Saratoga Spittlebug—

íí\f^íÍAU

United States III Department of

Agriculture

Forest Service

Agriculture Handbook No. 657

Saratoga Spittlebug— Its Ecology and Management

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Cover (clockwise from top \eit)^Saratoga spittlebug; feedings scars; damage from spittlebug infestation; spittlebug nymph in spittlemass.

♦^ \^*

Saratoga Spíttiebug— Its Ecology and Management Louis F. Wilson, principal insect ecologist U.S. Department of Agriculture, Forest Service North Central Forest Experiment Station East Lansing, MI

United States Department of Agriculture Forest Service

Agriculture Handbook No. 657

April 1987

Contents

Page

Introduction 1 Biology, Distribution, Hosts, and

Damage 2 Description of the Insect 2

Taxonomy 2 Egg 2 Nymphs 2 Adults 3

Distribution 4 Hosts 4

Primary hosts 4 Alternate hosts 4 Interim alternate hosts 7

Life History and Habits 9 Egg stage 9 Nymphal stages 13 Adult stage 15

Host Damage 17 The feeding puncture wound 17 Physical injury 18 Physiological injury 22 Stand damage 23

Population Ecology, Dynamics, and Control 29 Ecological IVIodel 29 Population Dynamics IVIodel 30 Prevention and Control Tactics 35

Prevention 35 Cultural and biological control 35 Chemical control 35 Herbicidal control 37

Surveillance 38 Survey Methods 38 Risk 38

Risk-rating 38 Aerial risk-rating 39

Detection 40 Detection survey 40 Aerial detection survey 41

Evaluation 41 Feeding scar appraisal survey 41 Nymphal appraisal survey 41

Suppression 42 Predicting control date 42 Pre- and post-control appraisal survey ... 43

Page

Management 44 Management Guidelines 44 Socloeconomic Considerations 44

Timber 44 Wildlife 44 Water yield and quality 45 Recreation and visual quality 45

Selecting a Management Strategy 45 Unplanted sites 45 Plantations 46 Christmas trees 47

Literature Cited 48 Field Survey Forms 52

Risk-Rating Survey 53 Nymphal Appraisal Survey 55

Introduction

The Saratoga spittlebug, Aphrophora saratogensis (Fitch), is the most destructive sap-sucking forest insect pest of pines in eastern North America. Taxonomically described as a distinct species in the 1850's, it remained unnoticed until 1941, when Secrest (1943, 1944) linked red and jack pine mortality to feeding by spittlebugs. Pines planted extensively in the 1930's, especially in the Lake States region, provided abundant even-aged host material on which the adults fed. In addition, these pines were planted in old fields where abundant ground cover was available as food for the nymphs. This combination permitted the spittlebug population to reach epidemic levels, and many trees were killed in the early 1940's in Michigan and Wisconsin.

The spittlebug has damaged planted pines in most of the North- eastern States and in adjacent Canadian provinces. Its recogni- tion as a pest, in 1941, occurred almost simultaneously with the uncovering of the pesticide value of DDT. Because DDT was highly effective against the spittlebug, it and other chemicals were sprayed almost annually in the 25-year period following (Fowler and others 1986). In spite of these control programs, the spittlebug still ruins many pine stands each year and continues to affect thousands of acres of pine planted for pulp, timber, and other forest products. Much of the problem remains because pine is frequently planted on high-risk sites and because integrated pest management tactics and economic appraisals have not been available until recently.

Research has provided much new information about the behavior, habits, and ecology of the Saratoga spittlebug. Today management guidelines are available that are compatible with contemporary forest management practices. Such information is assembled and presented in this publication. It is divided into four major parts: • The spittlebug's biology, distribution, and hosts, and symp-

toms of the damage it causes. • The behavior of the insect as a population (this part includes

various preventive and control tactics, both historical and practical).

• Survey procedures useful for assessing spittlebug populations. • Management guidelines and socioeconomic considerations

useful for selecting appropriate management strategies.

Biology, Distribution, Hosts, and Damage

Description of the Insect

Taxonomy—Aphrophora saratogensis (Fitch) is in the order Homoptera, family Cercopidae, subfamily Aphrophorinae. The approved common name in North America (Entomological Society of America) is Saratoga spittlebug. The French name, used primarily in Quebec, is cercope Saratoga. Fitch (1893) originally described the species as Lepyronia saratogensis from specimens taken in Saratoga County, New York. Doering (1941) synonymized Ptyelus gelidus Walker from a list of Homoptera of 1851. Moore (1956) synonymized A. detritus (Walker) whereas Doering (1941) considered detritus to be distinct, but closely related to saratogensis. She says the two species can be separated by color; detritus lacks the broad white markings and other characteristics of the typical saratogensis adult. In this publication, I consider detritus as distinct from saratogensis, the former being a southern species, and the latter a northern species.

The genus Aphrophora was described by Germar in 1821 (Doer- ing 1930). Though Fitch (1893) originally placed saratogensis in the genus Lepyronia, he later pointed out that it should belong in Aphrophora because it fits Germar's description more closely. Still later, other taxonomists attempted to straighten out confu- sions in the genus and synonymies of saratogensis with mixed degrees of success (Walley 1928; Ball 1928, 1934; Doering 1930, 1941).

Egg—The egg is an elongate tapering ellipsoid, shaped somewhat like a teardrop—rounded at the large end and tapering to a curved blunt point at the other end (fig. 1). It averages about 1.8 mm long and 0.6 mm wide. Immediately after oviposition the egg is soft and depressed along the long axis; later it turns plump and turgid. At first it is a glistening light buff to yellow from pigment in the endochorion, but after over- wintering the pigment changes to red or purple. Eggs become deep red or deep purple if partially exposed to sun and weather.

Eggs dissected from gravid females contain well-developed embryos that average 0.6 mm long, the size at which they enter winter for their obligatory diapause (Giese and WUson 1957). Viable eggs more than a few days old contain a red spot that can be seen through the transparent chorion at the pointed end. The spot is spherical and appears to be granular, noncellular, and separated from the embryo by undifferentiated yolk. The spot apparently is the source of red pigment for the abdominal region of the first four nymphal instars.

Nymphs—The five nymphal instars range in body length from about 2.0 mm (first instar) to almost 8.0 nun (fifth instar). Because lengths overlap between succeeding stages, markings and head capsule measurements are more reliable distinguishing characteristics. Typical nymphs are shown in figure 2 and on the

Figure 1—Saratoga spittlebug egg.

front cover. Anderson (1947b) lists the following head capsule widths for the five instars:

Instar Width (mm) Range (mm)

1 2.0 1.7-2.1 2 3.0 2.8-3.5 3 4.3 3.7-5.0 4 5.8 5.4-6.5 5 7.5 6.6-8.1

The striking crimson abdomen is a distinct characteristic of the first four nymphal instars. The head, thoracic tergites, portions of the leg segments, and pleural lobes of the abdomen are dark gray to jet black. The median line on the head and thorax is light brown, as are the zones around the eyes and remaining portions of the leg segments. Following ecdysis, the dark pigment is absent for a short period and those parts usually black are then tan or whitish. The compound eyes are scarlet.

The degree of dark markings on the pleural region of the caudal abdominal segments are useful for identifying the first four nymphal instars (fig. 3). The abdomen of the^rji instar is entirely

V IV

FIRST INSTAR SECOND INSTAR

THIRD INSTAR FOURTH INSTAR

Figure 3—Abdominal markings on first four nymphal instars. Ttie abdomens are crimson, the markings dark gray to black. Roman numerals indicate segments.

Figure 2—Late-instar nymph of Saratoga spittlebug.

crimson with the gray-black pigment confined to the caudal tergite (segment IX). Pigment is found on all pleurites of the second instar, but most abundantly on segment VIII and also abundantly on segment VII. On the third instar pigment is most abundant on segments VI, VII, and VIII. On the fourth instar pigment is more abundant on segments IV to VIII, and the nymph shows early development of wing pads. The fifih instar (not shown in fig. 3) has a uniformly tan or dark brown abdomen.

Initially, the fifth-instar nymph has a pale red abdomen and a tan thorax, head, and legs. Later the entire insect becomes uniformly brown. As it ages further, it tends to darken to a deep mahogany. The crimson color actually remains but is masked by the melanistic pigment in the cuticle (Anderson 1947b).

Adults—Fitch (1893) originally characterized the adult Saratoga spittlebug. The adult is smoothly tapered and somewhat boat- shaped from a top view. Adults of both sexes are primarily brown but are marked variously with distinct tan, silvery-white, and creamy blotches, stripes, and bands. A distinct, irregularly mottled transverse silvery band highlights each hemelytron (anterior wing cover). The major distinguishing mark is a broad dorsal median cream-colored stripe on the vertex of the head that extends onto the pronotum of the thorax. The stripe is arrow-like in most well-marked specimens (fig. 4A and front cover).

Fitch (1893) discriminated both light and dark specimens, the latter form having an iilmost obsolete stripe. He saw others that

Figure A—!\/lorphological characteristics of the Saratoga spittlebug. A—Head showing arrow-shaped marking. B—Female sternltes and ovipositor. C—Maie sternltes.

graded between the two. Most, however, have some striping. Females are generally larger than males and readily distin- guished by their sword-shaped ovipositor (fig. 4B), which is about one-fourth the length of the abdomen. Females average 9.7 mm long (range 9.0-10.31) and males average 8.9 mm (range 8.0-9.5). Females not well marked with the median stripe can be separated from other species by the length of the vertex and the ratio of head length to pronotum length (Doering 1941). Males are readily separable from other Aphrophora by the shape of the genital plates (fig. 4C) as well as by markings.

Several spittlebugs occur on northern pines, but only the Saratoga spittlebug and the pine spittlebug Aphrophora cribrata Walker are abundant and economically important. The pine spittlebug, because it prefers Scotch pine and jack pine, is rare on red pine and does not require an alternate host. A. gélida (Walker) is another, rarer species that looks like, behaves like.

and is sympatric with the Saratoga spittlebug (Putman 1953). However, it lacks the cream-colored stripe on the head and thorax.

Distribution

The Saratoga spittlebug is native to eastern North America. The distribution generally corresponds to the range of its major native hosts. In the United States, it is present from Maine south to New Jersey, westward through Pennsylvania and the northern portions of Ohio, Indiana, and Illinois, and northwestward to Minnesota. It is probably not present in Maryland, Washington, DC, and southward (Doering 1941). In Canada, it is found in the southern parts of all the provinces from the east coast to Manitoba. Historically, the spittlebug has been a pest problem in the Lake States and Ontario and to a lesser degree in Penn- sylvania, New York, and Maine.

Hosts

The Saratoga spittlebug requires two different hosts for complete development and survival—one for the nymphal stages and one for the adult. The adult needs a conifer on which to feed, mate, and oviposit. The conifer, usually a pine, is called the primary (or adult) host. The nymph feeds on the sap of various woody and herbaceous plants of the forest floor beneath or adjacent to the conifer host. These hosts are called the alternate (or nymphal) hosts.

Primary Aiosis—The Saratoga spittlebug's primary hosts are pines but it sometimes feeds intermittently on other conifers, particularly when these other conifers are growing along with the primary host pines. Since the extensive planting of pines in the 1930's, red pine, Pinus resinosa Ait., has been the most important primary host from the standpoints of feeding preference and economic injury. Jack pine, P. banksiana Lamb., is the second-most important host. The spittlebug readily feeds on jack pine, and it stunts and kills some trees in both pure and mixed stands. More trees are usually killed in mixed stands of red and jack pines, however. Anderson (1947a) counted 5.5 and 1.9 feeding punctures per square centimeter, for the red and jack pines, respectively, suggesting a nearly threefold preference for red pine. Ewan (1961) also ranked red pines far above jack pines for spittlebug preference. He noted that in mixed plantings, even when red pines were severely injured or killed, jack pines rarely showed more than some dead shoots and appeared in little danger of dying or having their tops die. Also, jack pine usually dies from the spittlebug-associated burn blight fungus and not directly from the spittlebug.

Eastern white pine, P. strobus L., is another native pine that will support adult spittlebugs, but the insects seldom attack white pines when they are isolated from red or jack pines. Heavily injured white pines have been found near heavily infested red pines in Pennsylvania (Ewan 1961). I have noticed feeding punctures on white pines but have not seen flagged or dead white

pines. In one test, however, spittlebugs killed white pine shoots after a week of feeding in sleeve cages placed over white pine branches. Anderson (1945a) also suggested that eastern white pine is far inferior to red pine as a host. Using nymphal abundance on the alternate hosts beneath ñve adjacent pairs of red and white pines as an indicator of preference, he measured six times as many nymphs beneath the red pines (table 1). On sweetfem alone, nymphs per stem were seven times more abundant beneath red pine than under white pine.

Table '\—Saratoga spittlebug nymptial density beneath five adjacent pairs of red and eastern white pine trees'^

Nymphal host

No. of nymphs per plant

Red pine White pine

Sweetfern Aster Blueberry Bracken fern Barren strawberry Wild lettuce

3.5 .6 .5 .4 .3 .2

0.5 0 .2 .1 0

.1

iTaken from Roger F. Anderson, Biology of the Saratoga spittle insect, 1945.

Both Scotch pine, P. sylvestris L., and Austrian pine, P. nigra var. austríaca A. & C, are occasional primary hosts in Christmas tree or other plantations when alternate hosts are present. In a Scotch pine planting that showed heavy shoot flagging, the stand was infested by both the Saratoga spittlebug and the pine spittlebug, and the needles showed signs of Diplodia sp. infestation, which is frequentiy associated with pine spitflebug feeding.

Pitch pine, P. rígida Mill., was recorded as a host by Fitch (1893), and tamarack, Larix laricina (Du Roi) K. Koch, by Doering (1942). I have seen a few feeding punctures but no injury on tamarack.

Adult spittlebugs have been taken from balsam fir, Abies balsamea (L.) Mill., and northern white-cedar. Thuja occiden- talis L., when growing in the vicinity of infested red pines (Ewan 1961). No feeding on these conifers has been reported.

Alternate hosts—Hundreds of plant species likely qualify as alternate hosts of the spittlebug nymph. Ewan (1961) suggested that if a list were compiled, it would include nearly every herb, shrub, tree seedling, and fern growing in pine stands. This statement is almost valid, but some plants are so rare that they would not commonly become hosts of the nymphs.

Anderson (1947b) encountered and listed about 35 plant species that served as hosts during all or part of the nymphal period. Examining 91 one-tenth-acre plots in 60 red pine plantations infested with the spittlebug, Kennedy and Wilson (1971) recorded an abundance of about 30 species of plants covering the forest floor (table 2). Grasses and sedges were present in all plots and

Table 2—Abundance of understory vegetation in 91 Saratoga spittlebug plots in ttie Lower Peninsula of Michigan

Understory vegetation Scientific name

Graminea; Carex spp. Comptonia peregrina (L.) Coult. Rubus spp. Musci, Lycopodium spp.,

Cladonia spp. Soiidago spp., Aster spp.,

Potentilla spp., Rumex sp.. Centaurea sp., Anemone sp., Gaultheria sp., Achillea sp., Convolvulus sp., ef a/.

Pteridium aquilinum (L.) Kuhn Vaccinium spp. Fragaria Virginian a Dus. Prunus pumila L. fî/71/s spp. Hieracium aurantiacum L. Prunus spp., Sa//x spp.,

Populus spp.

Plots with these species

(%) Percentage of ground cover

Grasses, sedges Sweetfern

Brambles Mosses, lichens

Misc. forbs

Bracken fern Blueberry Strawberry Sand cherry Sumac Orange hawkweed Small trees, shrubs

Total

100

69 46

43

100 23 17 30 18 14

7

26

21 11

11

10 6 4 3 3 2 2

100

covered an average of 26 percent of the ground. Sweetfern and brambles together occupied about 32 percent of the ground cover; 69 percent and 46 percent, respectively, of the 91 plots contained these species. The remaining 42 percent of the ground cover consisted of other miscellaneous plants such as forbs, ferns, shrubs, small trees, mosses, and lichens (table 2). Secrest (1944) specified that sw^eetfern was the principal nymphal host, and Ewan (1961) believed that both sweetfern and brambles were necessary for spittlebug population buildup. They believed that other host plants were less important but could contribute to population increase where they were abundant.

Wilson and others (1977), after extensive host preference tests, concluded that the ground cover plants in pine stands vary in their support of nymphal development and survival. They categorized the understory vegetation as plants that support the nymphs through full development, plants that support the nymphs through part of their development, and plants that do not support nymphs during any part of their development (table 3).

Several plant species provide suitable conditions for complete nymphal development and are the true alternate hosts of the spittlebug. Sweetfern, brambles, and blueberry are the most numerous of the true alternate hosts in the Lake States region. Nymphs survive best on sweetfern. All other true alternate hosts, except willow, do not support nymphs as well as sweetfern. Survival on willow is exceptionally high, surpassing sweetfern in most cases. This suggests that willow also might be capable of supporting high population buildup. However, young willow is rare in pine stands, occupying only about 2 or 3 percent of the forest vegetation, and sufficient numbers of willow are seldom available to permit high population buildup.

Other plants able to support nymphs through their ñill developmental period are less abundant than sweetfern, brambles, and blueberry, and also appear to have less survival value for the nymphs. Sheep sorrel and old-field cinquefoil are particularly poor hosts and are usually abandoned long before the nymphs mature.

The following discussion gives more information on the specific plants that support ftill nymphal development and includes observations on the survival rates of nymphs on different species. Unless specified, the information is from Kennedy and Wilson (1971) and Wilson and others (1977).

Sweetfern—Most investigators have concluded that sweetfern is the principal alternate host plant of the spittlebug (fig. 5 and back cover). Anderson (1947b) easily reared adults on this species from third and fourth nymphal instars, and he and other investigators noted that this species had large spittlemasses and abundant nymphs in the fifth stadium. Wilson and others (1977) reported that sweetfern pollen was nearly completely shed and buds were beginning to swell when nymphs eclosed and began to seek hosts. First-instar nymphs avoid the old stems and search out first- or second-year stems for feeding. Nymphal survival is always excellent if clusters have at least some young stems. The nymphs feed on both old and new shoots after the third instar.

Willow—Anderson (1947b) notes that willow (Salix humilis) was an excellent alternate host and found more last-instar nymphs on it than on sweetfern. He also easily reared fourth instars to adulthood on this plant. Leaves of Salix are just opening when the nymphs eclose. Late instars feed on old stems but all stages prefer the young suckers. The survival rate is very high, ex-

Table 3—Plants supporting and not supporting Saratoga spittlebug nymphal development

Common name Scientific name

Plants supporting full nymphal development (true alternate hosts)

Sweetfern Willow Bramble Orange hawkweed Low blueberry Sourtop blueberry Golden rod Sheep sorrel Old-field cinquefoll Spotted knapweed Everlasting Meadowsweet Wild lettuce Prairie ragwort

Comptonia peregrina (L.) Goult. Saiix spp. Rubus spp. Hieracium aurantiacum L. Vaccinium vacillans Torr. Vaccinium myrtilloides Michx. Solldago spp. Rumex acetosella L. Potentilla simplex MIchx. Centaurea maculosa Lam. Antennaria neglecta Greene Spiraea alba Du Roi Lactuca canadensis L. Senecio piattensis Nutt.

Fly honeysuckle Scarlet painted cup Common anemone White clover Lambkill Wlld-ralsin Gray birch Black chokecherry Canadian everlasting

Lonicera canadensis Marsh. Castilieja coccínea (L.) Spreng. Anemone canadensis L. Trifolium repens L. Kalmia angustifolia L. Viburnum cassinoides L. Betuia populifolla Marsh. Pyrus melanocarpa (Michx.) Willd. Antennaria canadensis Greene

Plants not supporting nymphal development (non-alternate hosts)

Grasses Sedges Lichens Mosses Clubmoss Leathery grapefern Violet

Gramineae Carex spp. Cladonia spp. Musci Lycopodium spp. Botrychium multifidum (J. F. Gmel.) Viola adunca Sm.

'Taken from Roger F. Anderson, The Saratoga Spittlebug, 1947 and J.P. Linnane and E.A. Osgood, Controlling the Saratoga Spittlebug in Maine, 1976.

Plants supporting partial nymphal development (Interim alternate hosts)

WIntergreen Swamp thistle Upright cinquefoll Bracken fern Common mullein Figwort Common yarrow Westen yarrow Shinleaf Trailing arbutus Silvery cinquefoll Aster Wild columbine Dandelion Pearly everlasting

Wood anemone Strawberry Grasses (few species)

Gauitheria procumbens L. CIrsium muticum MIchx. Potentilla recta L. Pteridium aqulllnum (L.) Kuhn Verbascum thapsus L. Scrophularia lanceolata Pursh Achillea miilefolium L. Achillea lanuiosa Nutt. Pyrola asarifolia MIchx. Epigaea repens L. Potentilla argéntea L. Aster spp. Aquilegia canadensis L. Taraxacum officinale G.H. Weber Anaphalis margaritacea

(L.) C. B. Clarke Anemone quinquefoiia L. Fragaria virginiana Duchesne Gramineae

Plants supporting at least partial nymphal development^ '■^-^jfà^ " : ,*^^^p<î

Upland willow Fire weed Quaking aspen Bastardtoadflax Daisy fleabane Smooth goldenrod Dwarf goldenrod Low bindweed Large-leaved aster Barren strawberry

Bush honeysuckle Pussytoes Common lousewort BIgtooth aspen Whorled loosestrife Common evening-

primrose Beaked hazel Smooth rose

Salix humills Marsh. Epiiobium angustifollum L. Populus tremuloldes MIchx. Comandra umbellate (L.) Nutt. Erigeron strlgosus Muhl. Solldago júncea Ait. Solldago nemoralis Alt. Convolvulus splthamaeus L. Aster macrophyllus L. Waldsteinia fragarioldes

(MIchx.) Tratt. Diervilla lonicera Mill. Antennaria canadensis Greene Pedicularls canadensis L. Populus grandidentata Michx. Lyslmachia quadrifolla L.

Oenottiera biennis L. Corylus cornuta Marsh. Rosa blanda Ait.

Figure 5—Sweetfern plant, the major alternate tiost of the Saratoga spittlebug.

ceeding that on sweetfern, suggesting that willow is the best of all nymphal hosts.

Brambles—Anderson (1947b) reared fourth-instar nymphs on brambles, and he detected fifth-instar nymphs in numbers second only to those on sweetfern and willow. Although the nymphs establish on brambles shortly after eclosión, the leaves are less than 0.6 cm long, and new-growth canes are from about 2.5 to 5.0 cm above the ground. Young nymphs feed on old canes first and move to new ones in the second and older instars. The survival rate is moderate to high on brambles.

Orange hawkweed—Anderson (1947b) readily reared nymphs to adulthood, beginning with the fourth instars, on orange hawkweed. Ewan (1961) considered this plant one of the principal spittlebug alternate hosts, but Kennedy and Wilson (1971) showed that it was not related to high population buildup. At nymphal eclosión, new hawkweed leaves are from 2.5 to 7.6 cm long. Previous year's leaves are present but are often flaccid or partly injured from freezing. Nymphs in all instars readily establish on this host, and the survival rate is generally high.

Blueberry—Anderson (1947b) placed fourth-instar nymphs on blueberry but was unable to rear them to adulthood. However, he noted firth-instar nymphs feeding on blueberry plants. Nymphs normally establish on the older woody stems, year-old stems, and new shoots. At eclosión, the new stems are from 0.6 to 2.5 cm tall and leaves are about 0.6 cm long. The new stems are preferred and most nymphs move to them by the end of June. Survival to adulthood is moderate on blueberry.

Golden rod—Anderson (1947b) reared spittlebug nymphs from the first instar to adulthood on goldenrod. Most goldenrod plants are from 2.5 to 7.6 cm tall at the onset of nymphal eclosión. Survival is generally good to excellent on the succulent species, but older nymphs usually vacate the "woodier" goldenrod and search for more suitable hosts.

Sheep sorrel—Sheep sorrel often grows in large clusters near red pine, and nymphs readily establish on it after eclosión. The plant appears healthy and succulent at eclosión time. By the time of the insects' third stadium, however, the nymphs usually vacate the plant in favor of more suitable hosts. Sheep sorrel supports a small percentage of the insects to adulthood, but it acts more like an interim alternate hosts (see below) because it mainly supports the young nymphs.

Old-field cinquefoil—Olá-ñdá cinquefoil is about 5.0 cm tall at nymphal eclosión, and the nymphs readily establish on it. Nymphs generally vacate cinquefoil in the later instars but can complete their development on it if there are no other suitable plants nearby. The survival rate to adulthood is moderate.

Spotted knapweed—Clusters of spotted knapweed are about 12.5 cm tall at nymphal eclosión. Nymphs easily establish on this host and develop to adulthood with moderate survival. Some nymphs in the older instars vacate knapweed for more suitable hosts.

Everlasting—Anderson (1947b) was unable to rear first-instar nymphs to adulthood on everlasting, but he noted a few plants had fifth-instar nymphs on them.

Meadowsweet—Meadowsweet has leaves about 1.2 cm long at the onset of nymphal establishment. Old and new stems appear equally attractive to nymphs. Most nymphs remain on the host to adulthood, and survival is moderate. Wilson and others

(1977) noticed that nymphal counts increased fourfold on some plants during the last instar, indicating a possible attraction for the older nymphs.

Wild lettuce and barren strawberry—Anderson (1947b) easily reared first-instar nymphs to adulthood on these hosts. Wilson and others (1977) reared only one insect to adulthood on wild lettuce.

Interim alternate hosts—Numerous understory plants support the nymphs through only parts of their development because of asynchronous life cycles of the insect and the host, nutrient or chemical changes, and/or various physical properties of the plants. These we have designated as interim alternate hosts and many of these species may collectively occupy a large proportion of the ground cover in pine stands. Bracken fern is one of the most common of these species. Interim alternate hosts appear to be valuable to the nymphs because they provide some food and/or shelter from the elements and their enemies. Also, their presence most likely increases the nymphs' chances for survival, especially when true alternate hosts are sparse.

Nymphs may utilize interim host species during the early or late portion of their development. For instance, the bracken fern, especially in shaded areas, is not always available to the nymphs at eclosión but is suitable as a host. In contrast, upright cinquefoil is available and highly suitable for early instar development but unsuitable for late-instar nymphs. The complete absence of true alternate hosts, which is unlikely, may interfere with the nymphs' survival and development to some extent, but nymphs can still survive by feeding on two or more species of interim hosts. For example, nymphs encountering upright cinquefoil shortly after eclosión could develop through the first or second instars on this plant, then vacate it and complete their development on a plant such as bracken fern.

Specific plants that support partial nymphal development, the interim alternate hosts, are described and also listed in table 3. In addition, Anderson (1947b) and Linnane and Osgood (1976b) listed and discussed numerous other hosts that support at least partial development (table 3).

Wintergreen—Anderson (1947b) noted a few young nymphs on wintergreen but later could not locate any fifth instars. This plant is woody in the spring and barely suitable for early nymphal feeding. In the absence of other hosts, some nymphs feed briefly on new shoots of wintergreen as they emerge. Survival is usually poor if the nymph stays too long on this species.

Swamp thistle—Nymphs have difficulty establishing on swamp thistle after eclosión because the leaves are in a tight rosette around the stem. Wilson and others (1977) examined 35 plants and concluded that the hairy or spiny leaves inhibit nymphal establishment for a week or more after eclosión. These spines spread out as the plant elongates, so second-instar nymphs are

able to establish and grow to adulthood on swamp thistle. Most late-instar nymphs, however, vacate the plant for more suitable hosts.

Upright cinquefoil—Nymphs readily establish on upright cinquefoil but most vacate it or die. In mid-June this plant becomes tough and woody, which may contribute to its failure to maintain nymphs beyond that time.

Bracken fern—Crosiers of bracken fern usually have not emerged above ground at the time of first-instar nymphal eclo- sión, and are thus not always available to the small nymphs. Wilson and others (1977) found that second- and third-instar nymphs would establish on this plant although they frequently vacated it for more preferred hosts. Spittlebug nymphs, however, sometimes remain on bracken fern from late May, when they are in the second instar, until adult emergence in July if these plants are in the vicinity of hawkweed or other favored alternate hosts. Anderson (1947b) reared a few nymphs from the fourth instar to adulthood and noted that only a small percentage of fifth instars inhabited the ferns.

Common mullein and /ygworf—Both these hosts support nymphs for a short period after eclosión but become unsuitable thereafter. The hairy nature of mullein probably repels the nymphs. Anderson (1947b) found a few nymphs spittled on common mullein but remarked that it was not a favored host.

Yarrow and s/7//7/eaf—These hosts easily support nymphs during the first half of their development. Mortality increases after that and those surviving readily vacate it for more suitable hosts. Both species appear highly unsuitable by late June, but Anderson (1947b) noted a few plants of one species of yarrow (Achillea lanulosa) with fifth instars.

Trailing arbutus and silvery cinquefoil—Nymphs establish and develop on these plants but usually die by the third instar if they don't move to other plants.

Aster and wild columbine—These plants support the nymphs through three-quarters of their development. Nymphs then vacate and do not reestablish on them, indicating that the conditions become totally unsuitable thereafter. Anderson (1947b) noted that first instar nymphs were abundant on Aster lindleyanus and A. macrophyllus but fifth-instar nymphs were very rare. Also, he was unable to rear first-instar nymphs to adulthood on either species of aster.

Dandelion, pearly everlasting, and wood anemone—These three plant species support nymphs from eclosión to the late instars, but all nymphs seem to vacate these plants by the last instar. Anderson (1947b) recorded only young nymphs on pearly everlasting and Anemone quinquefolia and older ones on dandelion and Anemone canadensis. His attempts at rearing first instars to adults on Anemone failed.

Strawberry—Nymphs readily establish on strawberry after eclo- sión when the new leaves are opening and the plants are from 5.0 to 7.5 cm tall. Survival, however, is poor. Anderson (1947b) found a few fifth instars on strawberry plants but was unsuccessfiil in rearing fourth instars to adulthood. Plakidas and Smith (1928) record a spittlebug species as a pest of strawberry in Louisiana but the pest was probably Aphrophora detritus Walker (Doering 1941).

Prairie ragwort—Anderson (1947b) was unable to rear nymphs from the first instar to adulthood on prairie ragwort. He found a few plants with last instars on them.

Other plants—Anderson (1947b) lists several additional plants on which he found spittlemasses with nymphs in some stage of development (table 3). He observed early-instar nymphs on common lousewort and late-instar nymphs on fire weed, quaking aspen, bastardtoadflax, daisy-fleabane, low bindweed, and bush honeysuckle. Further, he noted a few nymphs spittled on whorled loosestrife, common evening-primrose, beaked hazel, smooth rose, fly honeysuckle, scarlet painted cup, white clover, and bigtooth aspen. Wilson and others (1977) found a few young nymphs on low bindweed. Linnane and Osgood (1976b) list several alternate hosts common to the pine barrens of eastern Maine. Besides those found in the Lake States, they add lambkill, wild raisin, gray birch, and black chokecherry to the nymphal hosts list.

Part of the ground cover in pine plantations consists of sedges, grasses, lichens, mosses, and miscellaneous forbs upon which spittlebug nymphs do not feed; these plants are totally unsuitable as alternate hosts (table 3). For instance, after a diligent search Wilson and others (1977) found no nymphs on violet. And when placed on violet, the nymphs always abandoned it without feeding. Grasses also have always been considered unsuitable as alternate hosts. Wilson and others (1977), however, found first instars feeding on a few grasses in areas where forbs were scarce, and an occasional older nymph was observed feeding on grass even when other plants were available. These were isolated feedings; grasses certainly would not support nymphs for long.

The major full-development alternate host plants have been examined as to their importance by comparing red pine injury (as an index) to percentages of available alternate hosts (Kennedy and Wilson 1971). Not surprisingly, injury increased directly as the percentage of sweetfern increased (up to 45 percent, after which spittlebug injury leveled off) (fig. 6A). Therefore, sweetfern is important for spittlebug development or population buildup. Other fiill-development nymphal hosts (bramble, orange hawkweed, blueberry, etc.) collectively were also compared to pine injury. Interestingly, injury was not related to the availabil- ity of these hosts. That is, injury was always light no matter how abundant the plants (fig. 6B). Because Ewan (1961) ranked brambles and strawberry as primary alternate hosts, these were

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PERCENT MAJOR HOSTS (NO SWEETFERN)

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PERCENT BRAMBLES (NO SWEETFERN) PERCENT STRAWBERRY (NO SWEETFERN)

Figure 6—Relationship of adult Saratoga spittlebug injury to density of sweetfern (A) other alternate hosts (B-D). Numbers in the upper right corners indicate the number of plots measured.

individually compared to injury but also showed no relationship to injury and abundance (fig. 6C, D). Kennedy and Wilson (1971) thus concluded that sweetfern was the most important of the common full-development alternate hosts of the spittlebug.

Life History and Habits

The Saratoga spittlebug is univoltine—that is, it has only a single generation each year. The developmental period, however, varies somewhat. A 2- or 3-week variation of the life cycle, particularly in early spring, is not unusual over the insect's north-south range or where there are diverse seasonal weather patterns (fig. 7). For instance, nymphal development may take from 40 to 70 days in different years or at different latitudes. A few adults may emerge by the latter part of June and an occasional nymph may still be found in late August, indicating that stages tend to overlap broadly (Ewan 1961).

Egg stage—Eggs are laid from about mid-July to late September, which is most of the adult spittlebug's life. After adult eclosión, eggs mature for about a week before they are laid. The number of eggs laid usually peaks 2 or 3 weeks after

STAGE

EGG

N,

N2

N3

N4

N5

ADULT

EGG

WIN. APR. MAY JUNE JULY AUG. SEPT. WIN.

Figure 7—-Generalized life cycle of the Saratoga spittlebug averaged for several years for central Michigan.

most of the adults have eclosed. Eggs are present in the field from the onset of oviposition through fall and winter until late May, as much as 10 months.

The number of eggs laid by a female spittiebug is not known precisely because she may live for more than 2 months and lay eggs throughout that period. Anderson (1945a, 1947b) dissected spittlebugs weekly and counted the following number of fully developed oocytes:

Date (1944)

July 9-15 July 16-22 July 23-29 July 30-August 5 August 6-12 August 13-19 August 20-26 August 27-September 2

Mean number of eggs/female

5 0 1.3 5.0

12.8 5.2

12.8 10.7

He could not find fully developed eggs in young females until late July. Insects collected in August yielded an average of 9.7 eggs per female; some had up to 27 eggs and others were fully spent. Ewan (1961) dissected spittlebugs weekly and found an average of 14.6 eggs per female. He noted that the oocytes appeared to mature all at once, and suggested that the average he found was probably the full egg complement, or close to it. The exact fecundity of the spittiebug has not yet been determined, but it seems to be less than 30 eggs.

On red pine, eggs are deposited mostly under the bud scales. Red pine is ideal for oviposition because it has numerous large buds with loose scales that are somewhat free of a heavy pitch coating. On jack pine the buds are too resinous for oviposition sites; instead the eggs are laid in the needle sheaths. Secrest (1944) erroneously reported that eggs were laid in shallow slits or under the bark scales of sweetfem. Others have not observed this. Also, spurious reports have been made of eggs being found under the bud scales and bark scales of various hardwoods (Anderson 1947b, Eaton 1955). If true, this must be a rare occurrence, perhaps a result of population pressure. Red pine buds harboring eggs appear bumpy on the surface, and, when heavily laden, some eggs protrude from the ends of the scales (fig. 8). When scales are peeled back, two to ten eggs can be seen with their points upward and lying side by side in rows or clusters (Ewan 1961).

Eggs are laid on every whorl of young red pine, but many more eggs are laid toward the top of the tree than toward the bottom. Distribution is apparently related to large buds and loose scales, which occur on the upper whorls (fig. 9). Small, tightly closed buds are free of eggs no matter where they are located on the tree.

About 33 to 50 percent of the eggs are under the scales of the buds on the terminal shoots. These percentages are particularly applicable for red pine. The single, very large terminal bud may harbor 25 percent of the eggs on a tree. At high population levels numerous eggs can be collected from a large terminal bud, occasionally up to 50 or more. The first-whorl buds harbor another 10 to 20 percent of the egg population.

Figure 8—Saratoga spittiebug eggs protruding from scaies of a red pine bud.

237

Figure 9—Scfiematic of young red pine trees showing location and numbers of Saratoga spittiebug eggs, summed from seven moderately infested trees. T = terminal. Numbers 1-7 refer to wfiorls.

10

Egg distribution varies up and down the tree depending upon the insect population and tree size. Very lightly to moderately infested trees (about 10 to 90 eggs per tree) have 60 to 65 percent of the eggs on the terminal and first whorl (table 4). As the population increases, proportionately fewer eggs are laid on the upper whorls and more are laid on the lower, regardless of tree size (fig. 10). Also, large trees (or ones with several whorls of branches) have a broader distribution of the eggs than smaller ones. For example, three-whorl trees have more than half of the eggs on the terminal shoot. Trees with more whorls have about a third of the eggs on the terminal, with the rest distributed throughout the remaining branches (fig. 11).

Spittlebug eggs are aggregated or overdispersed on planted red pine trees (fig. 12) as indicated by Taylor's power law (1.00 is random) (Taylor 1961). This index for the spittlebug is 1.63 and indicates a strong aggregation, which may in part be due to distribution of alternate hosts and perhaps also to oviposition habits. Sweetfern, particularly, is highly clumped and the spit-

tlebug population tends to be higher in areas where sweetfern is abundant. If the adults remain fairly close to where they grew up and if the females lay most of their eggs on the same tree, some trees would receive many eggs and others few or no eggs—a situation encountered in overdispersed populations. Very mobile adults and single or small-batch egg deposition would encourage less aggregation. Spittlebugs, however, are poor ñyers, but they can dart from tree to tree when disturbed. This suggests that they do not move great distances. The position and proximity of the eggs under the bud scales indicates that the females lay several eggs before moving to a new site.

Eggs containing well-developed embryos overwinter in an obligatory diapause that normally ends after exposure to low temperature. Eggs collected in fall and held at room temperature or incubated at 80 °F do not differentiate beyond the embryonic stage in which they enter diapause (Ewan 1961). Giese and Wilson (1957) held eggs at 80 °F and after 2 years found them still viable but undifferentiated. Eggs collected in January or

WHORL Figure "ïO^Distribution of Saratoga spittlebug eggs on young red pine trees witti three to eight whorls for five population density classes ranging from 10 eggs per tree (VL = very light) to 90 eggs per tree (VH = very heavy). (C = current growth leader).

30 7-74 2

31—753 ► / 22

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12

r27

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3 WHORLS 4 WHORLS 5 WHORLS

Figure ^^\--Distribution of Saratoga spittlebugs on red pine trees with various numbers of whorls per tree (various population levels are combined).

6 WHORLS 7 WHORLS

later always developed, and nymphs hatched in 1 to 3 weeks after warming. Eggs collected in October did not hatch when exposed to 0 °F for 1 week, but they did hatch when held at 20 °F for 60 days (Ewan 1961). This indicates that a prolonged exposure to moderately subfreezing temperature is more effective in stimulating diapause release than a brief exposure to very low temperature. Cold shock normally initiates the termination of diapause, but chemicals may play a minor role under certain circumstances. Giese and Wilson (1957) reported a 50 percent greater growth of embryos in eggs subjected to a solution of macerated red pine needles. However, the eggs did not hatch.

The role of the red pine needle solution or other chemicals is uncertain because eggs collected in fall do not hatch, even when left inside red pine buds where resinous chemicals certainly occur.

The red spot, which develops in the egg shortly after deposition, remains unchanged until diapause terminates. It is largest (0.2 to 0.3 mm in diameter) from fall until spring and occupies about 10 percent of the volume of the egg. When weather warms, the red spot decreases and after a short period disappears. In the laboratory, Giese and Wilson (1957) noticed that the red spot

Table 4—Percenfagfe distribution of Saratoga spittlebug eggs on trees with six or seven whorls at five egg densities

Terminal and Very light Light Moderate Heavy Very heavy whorl (<11 eggs/tree) (11 -30 eggs/tree) (31 -90 eggs/tree) (91- -120 eggs/tree) (>120 eggs/tree)

Terminal buds 54 46 40 23 28 First whorl buds 11 14 25 20 14 Second whorl buds 23 11 17 23 25 Third whorl buds 2 24 5 14 11 Fourth whorl buds 4 1 3 8 5 Fifth whorl buds 6 0 6 7 8 Sixth and seventh whorl buds 0 5 4 5 8

Columns may not add to exactly 100 percent because of rounding.

12

100

MEAN Figure 12—Aggregation distribution of Saratoga spittiebug eggs based on ttie relation between intertree variance (s^) and mean (m) number of spittiebug eggs per tree. Dispersion index s^ = am''^'^ is based on Taylor's power law. Equation s2 = m indicates a random relation.

diminished in proportion to the increase in length of the post- diapausing embryo according to the formula Y = (0.847)(0.085)^, where Y is the diameter of the red spot and x is the length of the embryo in millimeters. The spot disappeared by the twelfth day. Giese and Wilson (1957) propose that the red spot is absorbed by the embryo and supplies the red pigment of the nymphal abdomen. Red pigment accumulates in the lateral- ventral region of the embryo's abdomen at the same time that the red spot shrinks.

About 3 to 5 days before hatching, a bulge appears on the con- vex surface of the narrow end of the egg. This marks the expan- sion of the egg-burster on the head of the pre-emergent first- instar nymph. When fully expanded, the egg-burster splits the chorion of the egg.

Nymphal stages — The nymphs first appear in early May and are present until late July, with some eclosing earlier or later depending upon the weather. Eclosión begins at the time red pine shoots begin elongating. Soon after, the pre-emergent nymph splits the egg chorion and then wriggles free. Though this process may take hours in the laboratory (Ewan 1961), in the field the nymphs usually free themselves from the eggs in less than 1 minute (Wilson and Kennedy 1974). Freed nymphs immediately begin wandering over the bud surface and up and down nearby needles without pausing to dry out their exo- skeletons, as most other insects do. If humidity is high or the sky is overcast, the nymphs may spend several minutes on the tree. If it is a dry, sunny, and warm day, they vacate quickly. Most nymphs drop directly to the ground or are blown off by gusts of wind.

13

Nymphal eclosión occurs during a period of about 2 weeks. Each day new nymphs begin to appear around 6 a.m. Peak eclo- sión occurs between 8 and 9 a.m. and declines the rest of the day, culminating before 4 p.m. (fig. 13). Nymphs apparently do not emerge overnight (between 4 p.m. and 6 a.m.) (Wilson and Kennedy 1974). About 33 percent of the nymphs hatch during the peak hour and about 85 percent hatch between 7 and 11 a.m. On warm, sunny days nymphs emerge only during the 3 or 4 hours of the early morning. On cool, cloudy, or misty days, the daily emergence period is extended into the afternoon.

ground. While feeding, the nymphs withdraw plant juices and excrete liquid waste (through the anal pore). The waste is pumped up with air to form the characteristic spittlemass (fig. 14 and front cover). This froth prevents desiccation and probably fends off most natural enemies. Nymphs soon die if de- prived of the spittle. Spittle averages more than 99 percent water by weight and contains sugars and amino acids that are leftover metabolites. Bacteria may inhabit the sugary medium; sooty mold will use it as a growth substrate. The pH of spittle ranges from 7.1 to 7.8 (Wilson and Dorsey 1957).

Morning is the least stressful time for the primary eclosión of insects, such as young spittlebugs, that dry out quickly. Moisture certainly is important, but it appears not to be the only factor because the relative humidity often reaches 100 percent at night and also on rainy afternoons, periods when the insects do not normally eclose. Non-optimum temperatures may also squelch eclosión later in the day.

Nymphs iimnediately search out the alternate host plants when they reach the ground. They move quickly over small forbs and grasses. Ewan (1961) showed that newly emerged nymphs can travel long distances in just a few minutes in the laboratory. Moving onto suitable small alternate hosts, they feed singly or in groups at the root collars or in the axils of the lower whorls of herbaceous, rosette-shaped plants. On large plants, they feed at the root collar or occasionally from 2.0 to 5.0 cm above the

0500 0700 0900 1100 1300 1500 1700

TIME (HOURS)

Figure 13—Nymphal eclosión period of the Saratoga splttlebug.

Figure ^ A—Spittlemass of Saratoga splttlebug nymphs.

The spittlemass of first-instar nymphs is only 3.0 to 4.0 mm across, but increases to about 13.0 mm as more spittle is added by the nymphs as they mature. Two or more nymphs on a single plant usually inhabit the same spittlemass. Average spittlemasses contain two or three nymphs, and large "community" masses—from 5.0 to 8.0 cm across—may contain from 10 to more than 50 nymphs of two or three different instars. Anderson (1947b) counted 40 and 51 first instars on two wild letmce plants and 25 and 30 on two asters.

Ewan (1961) estimated the average duration of the five nymphal stadia as 16, 7, 9, 10, and 15 days, respectively, or about 57 days for the entire growth period of an average nymph. Studies in the 1970's in Michigan indicate the average duration of the life of the average nymph as 53 days. Though these differ, one would expect slight differences from climatic, geographic, and annual variations.

Nymphs transform to adults outside the spittlemass on the stem or leaf of the alternate host plant. Ecdysis has not been de-

14

scribed for the Saratoga spittlebug, but molting is similar for most cercopids. Doering (1931) and Severin (1950) observed the following adult transformation of the closely related A. per- mutata Uhler.

The mature nymph leaves the spittlemass, crawls up the stem, and firmly attaches its claws to the bark. By flexing its last abdominal segment, it covers the lower surface of the abdomen and thorax with spittle, which glues these segments to the stem. As the nymph bends its head and prothorax downward, the soft membrane adjoining them splits along the dorsomedial line. It takes about 20 minutes for the insect to extricate itself; ñrst it pushes the prothorax through the slit, then the head and the rest of the thorax follow, and finally the anterior abdomen emerges. The now callow adult bends backward and hangs down for about a half hour while drying. When dry, the new adult bends forward, clings to the exuvium and disengages the tip of the abdomen. The entire process begins at about 8 a.m. and is mostly complete by 10:30 a.m.

Because the ratio of woody plants such as sweetfern and brambles to other herbaceous forbs may be 1:4 or more in favor of the latter, the nymphs understandably end up mostly on the forbs. As the nymphs age, however, they usually change alternate hosts one or more times as their needs and the hosts' suitability change. By the end of the third stadium, numerous nymphs have moved onto the woodier plants. Ewan (1961) reported finding at least 60 percent of the fifth-instar nymphs on sweetfern and brambles during routine samplng of thousands of acres of red pine stands.

Anderson (1947b) was first to note that nymphal density decreased on most herbaceous plants and simultaneously increased on sweetfern as nymphs aged. On nine of the most common forbs, the number of nymphs per stem decreased from 1.5 to 0.2 for first or fifth instars, respectively, whereas the sweetfern nymphal population increased from 0.3 to 5.0 for the same stages.

More detailed studies later revealed that more than 80 percent of the nymphs start out on the forbs and remain on them throughout the first and second stadia until early June. Emigra- tion to sweetfern and brambles begins shortly thereafter and continues until late June—the approximate period of the third stadium. From a study in 1956, Ewan (1961) noted that the nymphs on sweetfern and brambles averaged about 17 percent on June 4 and 5, and about 50 percent on June 8 and 9, and about 80 percent at the end of June (fig. 15). This was a definite emigration from the herbaceous plants to the more woody plants and not a differential mortality of plants or nymphs because both the kinds of plants and numbers of nymphs remained stable throughout the month. The directed nature of this movement is particularly apparent when one con- siders that sweetfern and brambles accounted for only about 14 percent of the alternate hosts.

Nymphal density throughout pine stands differs greatly in space and time because of several variables. Eggs are on the trees, so the numbers, size, species (mixtures), and distribution of the trees influence where nymphs will be at eclosión. Eggs, too, are highly aggregated (see fig. 12), which immediately causes the nymphs to be overdispersed right after eclosión. Taylor's power law index for nymphs is 1.42 (random = 1.00), indicating a moderate degree of aggregation (fig. 16).

Most nymphs drop down from the trees, so first and second instars are aggregated close to the trees. Wind carries some nymphs a short distance from the trees, and nymphs on taller trees subjected to high winds during eclosión could be carried long distances before settling on hosts. As nymphs age they move about and emigrate to the woodier alternate hosts. All of these and other factors give the nymphs an uneven distribution in a stand as a whole. In addition, in stands that have openings or a low density of plants, or in areas where trees are more than 10 or 12 ft (3.0 or 3.6 m) apart, there is a population gradient spreading outward from each pine host. Ewan (1961) counted late-instar nymphs on sweetfern in concentric rings around red pine trees and found a decreasing gradient outward. The alternate hosts under the trees averaged more than five nymphs per plant, whereas those 10 ft (3.0 m) away from the trees averaged only one per plant (fig. 17). The gradient disappeared in denser stands having a thousand or more trees per acre when the distances between their crowns were less than 4 or 5 ft (1.2-1.5 m). The latter stands, however, are exceptions if infested by spittlebugs, because more appropriate alternate hosts tend to be in the open. Spittlebugs ftirther open up the stand as they weaken and kill trees. A nymphal gradient also occurs in large openings within a stand or along the edges of heavily infested stands. Anderson (1947b) counted nymphs on sweetfern plants from the edge of red and jack pine plantations out to 100 ft (30.5 m) and obtained a curvilinear gradient (fig. 18). Addi- tionally, he got similar results when counts were made in the vicinity of scattered large (12 to 16 in. or 0.3 to 0.4 m d.b.h.) jack and red pine.

Wilson and Hobrla (in press) showed that the nymphs could be sampled reliably for surveys if the ground was considered as a uniform substrate. Using 0.1-milacre samples taken randomly, they were able to predict the mean number of nymphs from the percentage of samples infested (fig. 19).

Adult stage—Adults begin to appear in late June or early July, and most have emerged by late July. Populations of adult insects remain constant for a week or two and then decrease at a rate of about 15 percent per week thereafter until late Sep- tember. Sometimes a few residual insects can be found in late October or until the first killing frost.

In preparation for eclosión, the fully developed nymph climbs onto a leaf of the alternate host and waits until its exoskeleton splits. Ewan (1961) speculated that transformation probably oc-

100

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NYMPHS ON SWEETFERN AND BRAMBLES

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Figure AS—Location and movements of Saratoga spittlebug nymphs during June.

15 20 25 30

JUNE

curred at night. Soon after drying, the newly formed adult flies to the pine host and seeks out feeding sites. Copulation occurs within a few days, and the peak of egg laying 2 or 3 weeks later.

At the beginning of adult transformation, males slightly outnumber females, but within a few days the sex ratio approaches 1:1. A collection of 1,088 adults taken in Wisconsin over 10 weeks gave a sex ratio (female/male) of 1.00:1.12 (Ewan 1961). Anderson (1947b) sexed 3,100 adults from 18 separate collections to get a ratio of 1.00:1.18. I sampled adults in Michigan for 4 years by sweep-netting and whole-tree bagging and obtained the following sex ratios from 4,595 adults:

Period Female/Male

mid-July 1.00:0.90 late July 1.00:1.06 early August 1.00:0.92 mid-August 1.00:0.83 late August 1.00:0.81 entire season 1.00:0.94

Most sweep-net collections showed a preponderance of females, but the whole-tree counts alone gave a sex ratio of 1.00:1.02 or nearly a 1:1 ratio. Sweep-netting probably biases the sex ratio slightly towards females because they spend some of their time ovipositing on the buds and are therefore more apt to be captured than males. Ewan (1961) noted that in September the total population drops to less than 10 percent of that in July and then the females outnumber the males 2 to 1.

When the weather is favorable, the adults spend most of their time feeding on the hosts' needle-bearing shoots. They nestle down between the needles, facing outwards, and insert their mouthparts through the cortical tissue of the shoots and branches. They feed all over the tree, including the needle- bearing portion of the mainstem, but prefer 1-year-old internodes in the upper crown. Once settled, adults may feed for several hours, but if disturbed, they spring away and fly to a new host. Each adult makes from 2 to 5 feeding punctures each day, with an average of about 2.6 per day (Ewan 1961). Feeding frequency peaks during late July and early August,

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Figure ^ 6—Aggregation distribution of Saratoga spittlebug nymphs based on the relation between intertree variance (s^) and mean (m) number of spittlebug nymphs per 0.1-milacre sample. Dispersion index s2 = am ^ ^2 /g based on Taylor's power law. Equation s^ = m indicates a random relation.

MEAN

when each adult makes about 3.5 punctures per day. Mid- September feeding generally drops to 1.5 punctures per day.

Adults are active during the warmest days or parts of days. All activity declines during cool and/or wet weather and nearly stops at 15 °C. Consequently, there is little movement or feeding at night and in the cool of early morning. Adults are active only during the warmest parts of the day in September and October. They are easily hand collected when the temperature is at or below 15 °C.

Adult spittlebugs aggregate on trees to about the same degree as nymphs congregate on the alternate hosts. Taylor's power law as an index of aggregation gives 1.42 (1.00 = random), which is a moderate aggregation and the same index as that for the nymphs (fig. 20).

Host Damage

The feeding puncture wound—Only adult spittlebugs damage pine. While feeding, the stylets of the adults' mouthparts enter and pass through the cells of the shoot cortex, penetrating to near the cambium. The stylets are narrow and leave little evidence of a feeding puncture wound on the bark of the shoot. Fresh punctures, however, can be detected if the shoot is inspected closely. The punctures can be traced in the inner bark by a discoloration that delimits them. Occasionally, small resinous droplets may appear at the wound following withdrawal of the stylets (Anderson 1947b). Light infestations of the spittlebug are difficult to detect, but heavy feeding occurring over several seasons leaves the shoot surface uneven and lumpy. This is particularly noticeable as the tree loses vigor.

17

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Figure M^Density of Saratoga spittlebug nymphs relative to distance from pine tree.

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DISTANCE FROM PINE PLANTATION (FEET)

Figure 18~De/7s/iy of Saratoga spittlebug nymphs on sweetfern relative to distance from an infested pine plantation.

The feeding puncture shows no immediate evidence of injury in the shoot, but about 17 hours later a slight tannish discoloration appears at the cambial-xylem interface (Ewan 1961). During the next few days this area darkens and broadens into a reddish and somewhat squarish blotch from 3.0 to 4.0 nmi across. Close ex- amination shows the blotch as a resin-filled pocket of necrotic tissues in the phloem and cambium (fig. 21 and front cover). As the shoot continues growing, a disruptive pitchy area develops in the xylem adjacent to the injured cambium. Still later, the injury is gradually repaired by proliferation from healthy cells nearby,

but the pitchy defect or scar remains permanently in the xylem as a small block to conduction. The defect also spreads up and down the shoot, leaving a dark streak up to 3.6 cm long in the xylem (Kennedy and Wilson 1971) (fig. 22).

On repeatedly attacked trees, the injured cambium may not heal over for two or more growing seasons. Slow healing leaves a pitch-filled necrotic streak that extends through two or more growth rings and terminates in a cuplike scar in the phloem (fig. 23A and B). These scars may be several millimeters across and are detectable externally as depressions and pitch-filled pockets in the bark. In trees nearing death, large scars contribute 10 to 20 percent of the injury to the current year's wood (Ewan 1961).

Healed-over scars show considerable histological disruption. The tracheids near the scar are malformed, and xylem cells just beneath the affected cambium are arranged with their long axes in a circumferential plane (fig. 23D) rather than in the normal plane parallel to the shoots' long axes (fig. 23C). Each scar, ex- clusive of surrounding abnormal tracheids, blocks from 1 to 5 percent of the conductive area of the xylem (Ewan 1961).

Necrosis of the cortical tissues following feeding is apparently due to a heat-labile substance—probably an enzyme contained in the spittlebug's salivary glands. Micro-organisms are probably not responsible for the tissue necrosis and scar formation, even though the spittlebug may transmit burn blight disease, which is caused by the fungus Chilonectria cucurbitula (Curr.) Sacc. (Gruenhagen and others 1947).

Feeding wounds occur in a definite horizontal gradient on both red and jack pine trees. Ewan (1953) showed that the spittlebug prefers feeding on the first internode and its preference decreases down the stem and inward toward the stem on red pine branches (fig. 24). This excludes the leader and current growth shoots, which always have the lowest wound densities. The gradient is consistent throughout the crown at any branch level and holds true at all feeding densities. Anderson (1947a) noted a similar gradient for jack pine, but proportionately more feeding wounds were found on the current growth compared to red pine.

There is practically no vertical gradient between branch whorls on the upper to lower portion of red or jack pine trees. That is, feeding wound counts on any internode on the upper crown are nearly the same on a comparable internode lower on the tree (fig. 24). Also, feeding wound densities are the same between the top and bottom surfaces of the branches. However, from 25 to 40 percent more feeding injury is visible in the phloem than on the xylem surface, and the percentages generally increase on progressively older growth (Ewan 1953).

Physical injury—Early injury is entirely hidden from view, so that subclinical or subeconomic damage to the tree cannot be easily assessed at any time during a spittlebug infestation. When

18

o 0.1 0.2 0.3 0.4 0.5 0.6 0.7

PROPORTION INFESTED 0,8 0.9 .0

Figure 19—Mear? number of spittlebug nymphs per 0.1-milacre sample predicted by percentage of samples infested. Values of n are confidence bands for sample sizes.

flagging and other gross symptoms of injury become obvious, the threshold of economic injury has been surpassed. Gross injury may occur in only 2 years when a spittlebug population rises rapidly. A spittlebug population, however, may build up slowly over several years so that injury remains less obvious. One early indication of subeconomic injury is a growth change in terminal and lateral shoot elongation (Benjamin and others 1953). Growth, of course, can be shortened by many adverse or climatological factors such as poor soil, drought, etc., but then growth is shortened for all trees in the stand. That is, the shoots

of weak trees grow in the same proportion to those of more vigorous trees. Hence, if the length of the lateral growth is compared to the length of the terminal growth for the same year (L/T ratio) for each branch whorl on the crown, and then these ratios are plotted on a graph, a normal tree will show an in- clined or sloped growth pattern (ñg. 25). Spittlebug-injured shoots are far short of their potential length. When plotted, the L/T ratios for injured trees will produce a nearly horizontal growth pattern (fig. 25). This pattern then indicates evidence of subthreshold spittlebug injury.

19

MEAN Figure 20—Aggregation distribution of Saratoga spittlebug adults based on the relation between intertree variance (s^) and mean (m) number of spittlebug adults per tree. Dispersion index s^ = 3011*2 is based on Taylor's power law. Equation s^ = m indicates a random relation.

Figure 2A—Adult spittlebug feeding puncture wounds on wood of pine shoot.

Figure 22—Two adult spittlebug feeding scars showing longitudinal streaking in the xylem.

20

1 P app^H*' ■ ^^^"ii^^^^^^^B

^r '■" ■ 1 ÄJL-N_. -*'».^

1^ '^1

^H^'%

\

1 h ■ÉÉ Figure 23—Adult spittlebug feeding scars: A—Pitch-filled pockets. B—Cross-section of sfioot. C—Normal sfioot tissue. D—Histological disruption of shoot from feeding injury.

21

5

4

3

2

UJ û I O g o LU t 4

O Ö CO

er UJ Û_

co LU (T Z) h- o ;z Z) CL

O

Û LÜ UJ

LEADER AND BOLE

CURRENT WHORL

■

JÊÊ THIRD i FOURTH

^^ WHORL

FIRST WHORL

J FIFTH

^^ WHORL

SECOND WHORL

-'—""^—1 1 1 1

SIXTH WHORL

2 3 4 2 3 5 6

INTERNODE AGE (YEARS)

Figure 24—Distribution of Saratoga spittlebug feeding-puncture wounds on red pine tree by leader and whorls.

The L/T ratio, however, is unreliable as an indicator of subeconomic injury following rapid population buildup because there is a 1-year lag between effects on the tree and adult feeding damage. Shoot elongation is complete by the time the spittlebug feeds, and the feeding injury will not affect the growth until the following season. Shoot flagging would then occur simultaneously with the change in L/T ratios, so the ratios would be of little value.

Heavy feeding for a year or two, or prolonged light to moderate feeding for several years, eventually takes its toll. Shoots progressively shorten and then the tips of branches and the tops of trees turn yellow and finally red (flag). Flagging is generally more pronounced on the tree tops but may occur anywhere on the tree. Branches twist and the bark of shoots becomes bumpy due to uneven healing and scarring from the feeding puncture

wounds and scars. Extensive feeding kills branches, the tops of trees, and eventually the whole tree (see cover). Surviving trees are stunted and have crooked boles with distorted branches and shoots (Lyons 1952, Heyd 1978) (fig. 26).

Sapling pines are more vulnerable to spittlebug injury, but even pole-size trees may be injured because heavy populations kill and stunt trees, thereby maintaining openings for alternate hosts. Heyd (1978) examined a 45-year-old red pine plantation that was still being attacked by spittlebugs where there were dense sweetfern patches. These injured trees averaged 7 m tall and had sweep, crook, forks, and large and extensive lower limbs. They greatly exceeded tolerance for utility poles, lumber, or other products (Guilkey 1958), and harvesting them for pulpwood would have been difficult because of loading, hauling, and chip- ping problems. Other trees averaged 11m tall and were free from deformities. They had been attacked years earlier, but had crowded out the alternate hosts when their crowns closed.

Crooks and sweep of the injured trees resulted from stem necrosis and lower whorl dominance. Added to this, the snow load compounded the amount of sweep and internal defects. Slices of the bole showed extensive damage in the wood and much compensatory lateral growth. Scars from numerous wounds left stained, resin-soaked areas that degraded and structurally weakened the wood (fig. 27).

Physiological /n/ury—Internal stresses and chemical im- balances result from spittlebug feeding in two ways: the adult withdraws plant juice, and the necrotic resin-filled feeding scars block water conduction.

During a single feeding the adult withdraws about 0.4 cm^ of plant juice (Anderson 1947a). Considering that moisture content of the bark and phloem ranges between 208 and 221 percent of the dry weight and the inner bark is 1.0 to 2.0 mm thick, the amount of liquid removed at each feeding equals the moisture in about 3.0 to 6.0 cm^ of inner bark. If moisture is not replaced, a shoot rapidly dries out and dies. Ewan (1961), however, showed that the liquid is replaced by rapid conduction immediately after feeding. Even heavy feeding injury is not evident right after feeding, but water conduction diminishes throughout the season as necrosis increases and vessels are blocked with resin, a condition that finally reaches a threshold where there is irreversible moisture deficiency. Anderson (1947a) showed that the effect of a feeding injury on water content of the shoot was an inverse linear relation for jack pine (fig. 28). Heavily injured red pine shoots begin yellowing when their moisture content drops to about 79 percent of normal—the permanent wilting point (Marshall 1931). Anderson (1947a) also showed that as the number of feeding punctures rises, water conduction drops drastically. Jack pine shoots with about 12 punctures/cm^ conducted only one-thirtieth as much water as similar shoots with less than two punctures. Shoots with more than 15 punctures/cm^ were unable to conduct water.

22

er

er ÜJ

LO

0.9

0.8

0.7

0.6-1

0.5

< 0.4 er UJ

0.2

0.1

0

INJURED TREE

Y = .6I3-.008X

NORMAL TREE

Y = .73I-.093X

2 3 4

BRANCH WHORL

Figure 25—Lateral-terminal elongation growth pattern for normal sapling red pine shoots and shoots responding to Saratoga spittlebug injury.

As pine shoots deteriorate from necrosis, the carbohydrate content changes. Moderately infested trees have only about 25 percent of the usual amount of sucrose in the phloem. Roots of the same trees have at least 30 percent less reducing sugars (Ewan 1961). This type of response by the tree is a typical result of a plugging of the xylem vessels followed by a shortage of water and reduced food production in the foliage.

Stand damage—Spittlebugs routinely kill or ruin large portions of pine stands, especially if trees are less than 5 m (16 ft) tall. Some stands, however, remain apparently uninjured even when spittlebugs appear to be abundant. Various factors of the stand profile are largely responsible for these differences.

Damage to a young pine stand or plantation, of course, depends primarily on the number of feeding adult spittlebugs. But tree size, too, is important in assessing or predicting damage because spittlebug-susceptible pines may differ in size by a factor of five or more. A doubling in tree height results in at least a tripling of the amount of foliage. Thus, the smaller the tree, the more rapid and severe will be the damage from a given spittlebug

population. Equally important is the number of trees in the stand, for the damage potential of a given insect population depends on tree density, so that fewer trees are damaged more.

Therefore, in order for the degree of tree damage that will result in a stand from a particular spittlebug population to be understood, the stand must be viewed as a whole, as a quan- titative expression of tree size and density. The total length of needle-bearing branches on each tree provides an accurate expression of tree size, but such measurements are too time- consuming. The product of tree height and number of branch whorls is easier to measure and correlates so closely to length of needle-bearing branches that it can be used instead (fig. 29).

An excellent expression of the total amount of spittlebug "food" in a stand is called tree-units—an index calculated from the product of mean tree height (in feet), the mean number of branch whorls, and the mean number of trees per unit area (usually an acre). Because most northern pines are symmetrical uninodal trees and often planted in rows, they easily lend themselves to the tree-unit index. A typical index, for example,

23

^^ f i

' *

m..

m ■if

^

'>"■■"%''

'»^^^JBmtf^^^^BÊ^^^^^^wl^^mmif '^ i^^% ^

Figure 26—Even-age sapling red pines distorted from Saratoga spittlebug feeding. A—Stunted and deformed tree in sweetfern pocl^et. B—Tree forl<ed at base with intertwining boles. C—Tree with enlarged lateral branch. D—Crooked tree.

24

Figure 27—Sapling red pine boies showing internai injury from aduit spittiebug feeding. A—Crool<ed tree showing scarring and partial recovery. B—Permanently crooked bole with extensive scarring. C—Straight bole with internal scarring. D—Bole with heavy surface scars.

25

5 10 15 20

MEAN NUMBER OF FEEDING PUNCTURES PER CM ^

Figure 28—Dens/iy of Saratoga spittlebug feeding-puncture wounds relative to moisture content of jack pine slioots.

for a well-grown dense plantation of red pine might be 36,000 tree-units per acre, based on trees 6 ft (1.8 m) tall with 6 branch whorls and 1,000 trees per acre. In contrast, a younger, poorly stocked stand having trees 3 ft (1 m) tall with 4 branch whorls and 300 trees per acre would have only 3,600 tree-units and thus be 10 times more vulnerable to injury by a spittlebug population of equal size.

Density of alternate host plants ftirther determines whether a spittlebug population is capable of increasing sufficiently to cause moderate or heavy injury. Kennedy and Wilson (1971) clearly showed that spittlebug injury increased directly as density of suitable understory vegetation increased (fig. 30). This ex- cluded mosses, lichens, and grasses, which are nonhosts. A stand with sparse or unsuitable understory vegetation will never be injured by the spittlebug, no matter what its size. Alternate host density must be at least "sparse-medium" before moderate injury occurs and more than "medium-dense" for heavy injury.

Ewan (1961) listed several factors responsible for favoring development of abundant alternate hosts: • Absence of trees in rocky or stumpy spots or other places

considered undesirable for planting. • Uneven planting so that areas even as small as 0.04 ha may

be considered as fiiUy stocked but still contain openings of 4 m^ (3.4 sq yd) or more.

• Failure of trees in localized areas due to various biotic and climatic factors in the early life of the plantation.

• The spittlebug itself, which stunts or kills the young trees and thereby creates its own opening.

In addition, sweetfem competes best on sandy sites—sites where pines are often planted and thus may be under stress from insufficient site requirements.

How many and what kinds of alternate hosts, then, are needed to support a damaging spittlebug population? Ewan (1961) indicated that epidemic populations occur in areas with 60 or more alternate hosts per milacre, but the presence of sweetfern and other woody plants enhanced the probability of an epidemic. Kennedy and Wilson (1971) showed that sweetfern was actually the only alternate host crucial for population build-up when alternate hosts were scarce. Numerous other woody and herbaceous alternate hosts, however, could support a high spittlebug population, even if sweetfern is absent.

Sweetfern must occupy from 35 to 40 percent of the ground, in lieu of other hosts, to produce spittlebug populations capable of inflicting moderate and heavy damage, respectively (Kennedy and Wilson 1971) (table 5). If sweetfern is absent, other host plants must occupy from 50 to 80 percent of the ground to obtain populations capable of the same damage levels. Sweetfern is thus twice as important as other plants as a component of infestations. Outbreaks without sweetfern apparently are rare because the ground must be lush with other host plants.

Sweetfern alone may occupy from 0 to 60 percent of the ground in a planting, but more often sweetfem is combined with other host plants.

Wilson and others (1977) showed that 63 out of 91 spittlebug research areas contained some sweetfem, and sweetfern occupied an average of 21 percent of the ground on the areas. However, blueberry and other tme altemate hosts occupied an average of 24 percent of the ground and interim altemate hosts averaged another 17 percent. Thus, the average planting with this combination has more than enough plants for potential heavy damage.

Table 5—Approximate percentage ground cover occupied by sweetfern and other alternate host plants needed to produce moderate and heavy damage by the Saratoga spittlebug

Alternate host Ground cover (o/o)

Moderate damage^ Sweetfern 0 10 20 30 35 Other plants 50 40 20 5 0

Total 50 50 40 35 35 Heavy damagez

Sweetfern 0 10 20 30 40 Other plants 80 70 30 10 0

Total 80 80 50 40 40

1 Moderate damage means pines show stunted growth, some crooked boles, and light flagging. ^Heavy damage means pines show crooked stems and branches, heavy flagging, top kill, and mortality.

26

ÜJ

no-

100

(/) 90 Lu X

80

< er ÛÛ 70

o 7^

fío Ul < III ÛD bO

ÜJ -I Û 40

ÜJ ÜJ Z 30

ü_ O

20 X h- co 2 lU

ÜJ

N= 104 Y= 2.729+1.145 X r = 0.954

10 20 30 40 50 60 70 80

TREE HEIGHT (FEET) X WHORLS

Figure 29—Tree height x whorls as an index of length of red pine needle-bearing branches.

X LiJ Q

>- £r

< ÜJ

S^IR^S^E SPARSE SPARSE ^,,„^ MEDIUM ,,,3, VERV^

DENSITY OF UNDERSTORY VEGETATION

Figure 30—Injury from Saratoga spittlebug relative to density of understory vegetation.

More than one-third of the ground in an average planting is covered by such nonhost plants as grasses and sedges. At best, these could provide shelter; more likely, they hinder nymphal sojourns between host plants. Nymphs forced to vacate interim host plants must find other interim hosts or true host plants to survive. While searching, they must encounter many nonhost plants. Thus, the higher the proportion of interim hosts and nonhosts relative to true hosts (especially sweetfem), the less chance for survival. Small nymphs likely should have the most difficulty surviving the rigors of host change when many nonhosts are available to hinder them. Young nymphs do not move about much or over long distances, probably because of these obstructions. Older nymphs wander more and tend to vacate both true and interim hosts in favor of sweetfern and, if present, willow.

Though adult counts are the only sure indicators of host damage, nymphal counts (in fourth and fifth instars) correlate closely

27

Í2 < O C/)

O 40

Lü U-

LJ_ O

cr Lü m

NYMPHS PER TREE-UNIT

Figure 31—Saratoga spittlebug nymphs per tree-unit as a predictor of adult feeding scar density. Feedings scars are expressed as the number per 4-inch section of the 2-year-old internode.

with adult injury and, therefore, can be used instead. Nymphal counts have distinct advantages because nymphs can be estimated more easily and more accurately than the adults, and counting nymphs permits sufficient time to prepare for control if needed. Plotting nymphs per tree-unit against adult feeding scar counts on red pine gives a highly significant linear relation (fig. 31). Thus, by knowing the number of tree-units in a red pine plantation, it is possible to predict the subsequent amount of tree damage from the nymphal population (Ewan 1958b).

Ewan (1961) reported that if infested trees exhibit 35 or more feeding scars per 4 in (10.1 cm) of 2-year-old internodes, shoot mortality and growth deterioration will generally occur the following year or two. An average of just over one nymph per tree-unit results in 35 adult feeding scars per 4 in (10.1 cm) of shoot (figure 31). The following formula derived from this figure can be used to estimate the number of feeding scars from the nymphal population in an infested red pine plantation: X = 31.3 a/b, where X is the number of feeding scars, a is the mean number of nymphs per 0.1 milacre, and b is the number of tree- units per 0.1 milacre.

28

Population Ecology, Dynamics, and Control

The outcome of spittlebug injury depends on various interactions of the spittlebug, the tree, the ahernate host, and the physical environment. The following ecological and population dynamics models show these various interactions in a sequential arrange- ment with the physical effects on the stand as the final result or outcome. Natural influences can and do modify the degree of variation of the components and are thus the factors in the overall change of the stand. This statement implies that the major or key influences can be manipulated in favor of appropriate forestry management practices.

Sweetfern competition stresses pines, apparently through moisture depletion (fig. 32). During dry summer periods, soil moisture is least in sweetfern-covered soils. And after heavy rains, soil water content drops fastest where there is sweetfern. The reverse is true for blackberry-covered soil. That is, sweetfern, blackberry, and grass use soil moisture at different rates. Moisture stress can be especially critical on the lightly podsolized sands that are highly suitable for sweetfern, and where red and jack pine are usually planted (Wilde 1946, Rudolph 1950).

Ecological Model

The ground cover association—the kinds and numbers of alternate hosts present—determines the extent of injury to the tree because of its affect on both nymphal survival and tree growth (fig. 32). Alternate hosts are obligatory to the insect, and sweetfern in particular is important for high spittlebug survival levels. Blackberry (Rubus spp.) and other ground cover plants are excellent alternate hosts; others are interim host plants, useful for only a portion of the nymphal period; and still others, such as grasses, are nonhosts. Greater density of the favorable nymphal hosts not only means a greater spittlebug population potential but also greater competition for soil moisture. Trees in the vicinity of sweetfern, even if spittlebug is absent, are shorter—their heights being in direct proportion to the density of the sweetfern. This is true for various age stands, and the effect is exerted in the same year of planfing and thereafter (Clements and others 1968). More seedlings die when planted in sweetfern pockets than in sod or blackberry patches. In strawberry patches, trees grow above average in height.

Sweetfern is a nitrogen-fixing plant (Ziegler and Huser 1963) and in small clumps may be beneficial to pines. However, where sweetfern is abundant, trees are much smaller, less numerous, and, therefore, highly susceptible to injury. Crown closure, which shades out sweetfern, takes much longer or may not occur at all.

Sweetfern may add to the stress of the tree when red or jack pine becomes infected with sweetfern blister rust, Cronartium comptoniae Arth. This rust uses sweetfern for an alternate host and is often fatal to pine seedlings or causes defects in saplings (Anderson 1963). Jack pine is the preferred host (Anderson and French 1964).

The surviving nymphal populafion determines the numbers of adults, and in turn adults provide the egg population that becomes the new nymphal population the following year. Each of these life stages has its own regulating determinants, which will be discussed under the insect-tree population dynamics submodel.

SHADING AND

STAND CLOSURE

QNOUNO COVER

ASSOCIATION

INSECT-TREE DYNAMICS

ADULT FEEDING

EXPOSURE

FEEOtNG SCAR

DENSITY

TRANSPORT BLOCKED

TISSUE NECROSIS

TREE SIZE AND

DENSITY

LOW-MODERATE VOLUME LOSS

LIMBINESS,CROOKS PARTIAL BR. FLAGGING

MODERATE VOLUME LOSS

WHOLE BRANCH FLAGGING TOP KILL

HIGH VOL LOSS TOP KILL, DEGRADE TREE MORTALITY

SWEEP AND BREAK

VULNERABLE TO SNOW DAMAGE

Figure Z2—Ecological model of the Saratoga spittlebug.

29

The number of insects reaching adulthood determines the degree of feeding. Considering that each adult makes more than two feeding punctures each day when the temperature is above 60 °F and that each may live 2 months or longer, it only takes a few adults to injure small trees. Injury, however, is relative and also depends on the amount of feeding surface available. That is, tree size and density are important and may vary in a stand by a factor of 10 or more. Small trees widely spaced are most vulnerable to injury because of the small feeding surface or tree-units.

Feeding puncture wounds form resin-filled scars that block water transport and cause moisture stress at various locations within the trees but especially in the upper crown where feeding is con- centrated (fig. 32). Seasonal rains, drought, and the water- holding capacity of the soil further contribute to the amount of moisture stress. Stressed trees grow short shoots and short needles, reducing photosynthetic potential. Stunted shoots yield smaller buds, which produce still shorter shoots in the year following. Small buds, on red pine at least, influence the oviposition pattern so that more eggs are laid on the top of the tree, at least until the top dies and stops forming buds. Stressed trees also synthesize inadequate carbohydrates and therefore produce less wood fiber.

Lightly stressed trees show only little volume loss, light branch flagging, slight crooking, and a slight preponderance of limbiness in later years. Caught early enough, spittlebug control on such trees will cause a rapid response and recovery. More stress, though, will yield considerably more damage and volume loss. Feeding injury then coalesces and subsequently blocks so much of the transport tissues that branches and tree tops die. Spittlebug control at this level should only be decided from the economic value and the management criteria planned for the stand. Conversions to other uses may be more valuable than direct insect control, if management plans will permit. High moisture stress is severely damaging to the trees and manifests as very high volume loss, severe degrade, and mortality. Con- trol of the insect at this level of injury is almost always imprac- tical. Such stands should either be replanted and managed for spittlebug, left for wildlife, or converted to other uses.

An additional effect of feeding occurs where the bole is heavily scarred and necrosis is rampant. Large dead areas in the wood cause the tree to compensate by growing on the opposite side of the stem. This often produces structurally weakened wood that may break over from external stresses. Moderately and heavily damaged trees and those with inordinate sweep or crooking break or bend readily from snow.

Additional stresses on the tree, of course, can occur from various insect pests and disease pathogens partial to pines. Bum blight fungus has been isolated from the necrotic areas around the spittlebug feeding puncture. Its role is uncertain as to

pathogenicity and subsequent decline of the tree. Several Aphrophora species are vectors of viruses such as Pierce's disease on grape and alfalfa, and A. saratogensis may transmit viruses but there is no record of such transmission at this time.

Population Dynamics l\/lodel

Numerous natural factors interact within the ecosystem to modify a spittlebug population, and when they are minimal, outbreaks ensue. Sometimes we are able to manipulate these variables and thus reduce spittlebug populations before in- tolerable damage occurs. The major agents of this ever-changing system can be shown through a spittlebug-pine population dynamics model (fig. 33), which is a submodel of the population ecology model (fig. 32).

The spittlebug egg—from the moment it is laid, through its long dormant period, and until the nymph hatches in spring—is affected by physical and biological agents that threaten its survival (fig. 33). For example, Milliron (1947a, 1947b) reared two parasitic wasps from spittlebug eggs. One of these, Ooctonus aphrophorae Milliron, is a mymarid, and it parasitized between 8.5 and 9.3 percent of eggs collected from two pine stands in September. Soon after parasitization, spittlebug eggs turn a dull whitish pink or lavender and the red spots vanish. Gradually the eggs turn gray-blue to blue-black and finally black. The eggs are exceptionally turgid, somewhat distorted, and appear larger than normal. Adult wasps issue through a small hole in the end of the egg between early September and mid-October.

The other wasp, Tumidiscapus cercopiphagus Milliron, is an aphelinid. Milliron (1947b) reared one or two adults from the eggs, and in one instance he watched a male and female escape from the same egg. The adults emerged in October from eggs collected in September. The parasitized egg is turgid and shiny black. Ewan (1961) reared T. cercopiphagus and recorded 3 and 5 percent parasitization from eggs collected in March. The parasite adults emerged 3 to 4 weeks after the spittlebug nymphs began emerging in the laboratory.

Egg predators are either rare or illusive. I have noticed large red mites on the eggs in spring but have never observed them feeding. Prolonged exposure to cold temperature is required for stimulating diapause release. Ewan (1961) found that 1 week at -18 °C was insufficient for hatching but 2 months at -7 °C prompted normal emergence. Death of the eggs from cold is unlikely because exposures far below freezing are common in northern pine stands. We have collected eggs following overnight temperatures of -32 °C with no apparent decrease in hatching.

Some eggs die during winter nevertheless. Some eggs may be infertile, and sometimes more than 50 percent do not hatch. Moisture may be involved, especially in the spring just prior to

30

MOISTURE

LOW TEMP

PARASITES PREDATORS

PREDATORS PARASITES DISEASES

MOISTURE TEMPERATURE

EGG

1 NYMPH,

SPITTLEBUG DYNAMICS

EGG

MIGRATION No - Nc

IN: TOUT

ADULT —^

. ^ - ^

1 SMALL

SAPLING LARGE

SAPLING

1

1 ALTERNATE

HOSTS 1

INSECTS DISEASES

ETC. TREE

DYNAMICS ' '

SEEDLING POLE + MATURE ^ W

Figure 33—Population dynamics model of the Saratoga spittlebug-pine ecosystem. W = winter, S = seed, N2-N5 = second to fifth nymphal instars.

hatching. Eggs collected and placed at 76 percent relative humidity (RH) did not hatch in the laboratory, while others placed at 100 percent RH did.

Wind may influence the survival of some eggs and thus the subsequent survival of the nymphs. The drying of bud scales and the expanding of shoots in spring loosen the eggs, which sometimes fall from or are blown from the tree. Once on the ground they may be more readily preyed upon by ants or other insects. Eggs may be blown some distance from the alternate hosts, causing the emerging nymphs to be unable to find food.

Moisture is a critical limiting factor for the young nymphs. Soon after hatching they must find an alternate host and cover themselves with spittle. Under laboratory conditions some newly hatched unfed nymphs will live 2 to 3 days if kept at 100 per-

cent RH (fig. 34) but will succumb in less than 12 hours at 30 percent RH (Ewan 1961). Nymphs reared on potted plants in the laboratory die within 24 hours even if forming spittle unless plastic bags cover the plants. In the field, humidity is generally high at hatching so that nymphs usually are able to cover themselves with spittle before desiccating. Spittlebugs hatch in the early morning hours, and thus can take advantage of cool temperature and high humidity—the best conditions for low évapotranspiration rate. Newly hatched nymphs seldom remain on the trees for more than a few minutes, favoring the ground where the humidity is higher (Wilson and Kennedy 1974). Once they are on the ground, the nymphs' immediate survival depends upon the proximity of suitable local humidity during the day. The humidity near the ground, especially under a tree, is higher than on the tree, and the rapid movements of searching nymphs normally can bring them to a host within a few minutes (Ewan 1961).

31

100

1007o R.H. (N = 229)

24 36 48

HOURS OF EXPOSURE

72

Figure 34—Survival of newly hatched Saratoga spittlebug nymphs when exposed to 30 and 100 percent relative humidity.

Late spring frost shortly after hatching is another critical factor affecting nymphal survival (Ewan 1958a). For example, in mid- May 1957, temperatures dropped to between -9 and -5 °C in upper Wisconsin and adjacent Michigan. Most nymphs were in the first instar and just forming spittle. The cold air penetrated the duff and destroyed about 85 percent of the population throughout red pine stands in the area. Similar stands further south lost less than 10 percent of the nymphal population; temperatures there had dropped to only -2 to -1 °C during the same period. Secrest (1944) noted a similar occurrence in 1942, in central Michigan. The nymphal population dropped considerably following a frost in early May when temperatures dropped to between —9 and -6 °C. Events such as this usually occur when the late frost is preceded by a week or more of 21 to 27 °C temperatures, which provide abundant day-degrees for spittlebug hatching.

Anderson (1947b) logged mortality of third-instar nymphs in the field when temperatures dropped to —2 °C and remained below 0 °C for 7 hours. About 80 percent of the nymphs died if their spittlemasses were above the duff. All nymphs protected by the duff, where the temperature dropped to only 2 °C, survived.

Anderson also tested unadapted third-instar nymphs to momen- tary exposure to freezing and subfreezing temperatures in the laboratory. He recorded no mortality at 0 °C, 50 percent at -2 °C, 75 percent at -5 °C, and 100 percent at -7 °C. Precondi- tioning the nymphs at 0 °C for 12 hours reduced mortality but did not lower the minimum at which 100 percent mortality occurred.

Subfreezing temperatures seldom affect the fourth and fifth instars because they appear in late June. Secrest (1944), however, tested fifth instars to determine their resistance to cold. At various temperatures and exposure times he found the following values:

Temperature (°C) Exposure (hr) Mortality (percent)

-6 to -5 2 60 -4 to -3 2 77 -8 to -2 2 89 -9 to -2 2 89 -9 to -8 1 100 -7 to -3 18 100

32

First- and second-instar nymphs can die during very hot, dry weather, especially in open stands with sparse ground cover that insufficientiy protects the nymphs. Many nymphs died in mid- June 1956 in northern Wisconsin, when daytime temperatures for 4 days soared to 32 °C and above—far higher than normal for that time of year. Subsequently, the humidity fell to critical levels in the open, drying up the small spittlemasses and the nymphs too. In two open-grown red pine plantations, nymphal populations in open, sunny locations dropped between 63 and 70 percent because of the hot spell. In contrast, nymphal populations protected by heavy shade dropped only between 16 and 32 percent (Ewan 1961). Linnane and Osgood (1976a) similarly recorded more than 60 percent reduction of third and fourth instars in Maine in June 1975, following 2 days with temperatures exceeding 32 °C and several days without rain. Hot, dry weather seldom occurs during the first or second nymphal stadia, and most young pine stands susceptible to spittlebug have dense undergrowth that protects young nymphs against drying.

Most fourth- and fifth-instar nymphs are less susceptible to drying. When nymphs are deliberately removed from spittlemasses and placed on the ground in full sunlight on hot days, they quickly seek hosts and reestablish themselves without difficulty. High temperatures during molting probably injure the nymphs more than at other times.

Predators certainly take their toll of nymphs, but records are scanty. The nymphs are probably attacked more often while moving among plants than when in the spittlemass. Secrest (1944) notes that several predators, including reduviids, sphecid wasps, pentatomids, damsel bugs, and spiders, have been observed capturing the sympatric pine spittlebug. Similar organisms certainly feed on the Saratoga spittlebug as well. Knull (1932) reported a parasitic fungus, Entomophthora aphrophora E. Rostr., that was highly destructive to the pine spittlebug and might also be an enemy of the Saratoga spittlebug. Anderson (1947b) found a few mummified Saratoga spit- debug nymphs but did not identify the pathogen.

Nymphal parasites are unknown. Drosophila azteca (Sturtevant and Dobzhansky) inhabits spittlemasses of the similar Aphrophora canadensis Walley but its role is unknown. It could be parasitic because the closely related fly Clastopteromyia inversa (Walker) (= Drosophila inversa Walker) is an ectoparasite of Clastoptera spittlebugs (Kelson 1964).

Migrations or movements between alternate hosts can variously affect nymphal survival. At such times nymphs are not only vulnerable to natural enemies but also to hostile environments. Hot, dry weather has the least effect on the larger nymphs, which do most of the moving. Distances between suitable hosts could be critical.

the pine stand. Although spittlebug adults are not strong fliers, they must move about a great deal, for nearly every pine stand contains some Saratoga spittlebugs. Immigration and emigration can certainly influence the ultimate population in a stand. Spit- tiebug movement is probably the most critical when new stands are planted near old infested ones or when they are planted among old brood trees from which the insects move onto the new trees.

The adult is commonly parasitized by Verrallia virginica Banks (Thompson 1977). Linnane and Osgood (1977) were the first to rear this adult parasite from the Saratoga spittlebug in Maine. This pipunculid parasitizes the callow adult during the second week of July. It has two instars—the first instar appears by mid- July, the second by the end of July. Larval development takes from 6 to 7 weeks, and all parasites have vacated their hosts by the first week in September. Parasite pupae overwinter on the ground (Linnane and Osgood 1977). Emergence coincides with spittlebug adulthood in early July.

Ewan (1961) probably collected the same species in Wisconsin, though he failed to rear adults for positive identification. Parasitism sometimes exceeded 60 percent in some years and locations. Consequently, he noted that areas of high parasitism showed large population declines the following year.

Most parasitized adults have one parasite larva, but some have more. Two male spittlebugs each had four parasites. It is difficult to imagine a parasite ftilly developing when two or more inhabit one insect because a single full-size second-instar larva almost fills the entire spittlebug abdomen. In fact, the abdomen often appears distended from only one large parasite. In early stages of parasitism, first-instar larvae were frequently found in spittlebugs that had functional gonads. Whittaker (1969) reports that some parasitized cercopids are still able to lay a small complement of eggs (4 rather than 30) before the second-instar larvae appear. By then the abdominal contents become atrophied, and the reproductive organs are the first to degenerate. Parasi- tized adults appear unhampered in their movements and still may copulate, though the abdomens are distended and the internal reproductive organs of one or both are gone.

There are few records of other spittlebug parasites. Anderson (1947b) and Linnane and Osgood (1977) reared a few unknown specimens.

Various organisms prey on spittlebugs. Spiders, especially the jumping species (Salticidae) and crab spiders (Thomisidae), cap- ture the adults. Adults sometimes fly into spider webs, and ants drag away spittlebugs. A large red mite frequently adheres to the adult in late August and September, but it probably is not important because most eggs are laid by then (Ewan 1961).

The adult stage, of course, is the stage that influences the tree, so that every factor that lowers adult survival indirectly affects

Dead adults are often infected with fungi of the genus Beauveria, which has a long list of insect hosts.

33

Mortality factors for the entire generation of the spittlebug are best understood in the form of a life table. The life table provides progressive mortality for each stage of the insect by identifiable factors—such as parasites, predators, temperature, etc.— that greatly reduce the population of each generation. Table 6 presents a spittlebug life table for 15 generations and varying population levels from light to heavy. The data for the life tables were taken in Michigan in the mid-1970's. The ranges of percent mortality in the last column of the table show the variation of the mortality for the major factors observed. Note particularly that parasitism was only from 1.6 to 11.9 percent, which is far less than the 60 percent observed by Ewan (1961) in some Wisconsin populations, and which seemed to keep the populations under some control. Other identifiable factors could contribute to population decline, but none that were observed seemed able to do so.

the shoots, makes them more susceptible to the fungus. Burn blight has not developed in stands where the spittlebug has been controlled. Over the years, the spittlebug has changed preference from jack pine to red pine because of planting practices. Since then burn blight has not been a problem, probably because it is only weakly pathogenic to red pine. Nevertheless, this situation could change as new strains develop and the tree's tolerance is overcome.

The health of the tree further influences its survival and its tolerance to the spittlebug and transmitted pathogens. Pines are hosts of many other insects and diseases sympatric with the Saratoga spittlebug, and any of these pests concurrently operating in a stand could compound the situation. The spittlebug affects small and large saplings (fig. 33) and so do many other pests.

The adult spittlebug is a parasite itself in the way it directly affects the tree through its feeding injury. Additionally, the adult poses an even greater threat to the tree through the possibility of transmitting disease pathogens. Cercopids are well-known vectors of viruses (Severin 1950, Delong and Severin 1950), and the burn blight fungus is a well-known associate of the Saratoga spittlebug adult. This disease sometimes occurs in spittlebug- infested stands, especially on jack pine where it has killed shoots, branches, and whole trees. Gruenhagen and others (1947) suggested that spittlebug is the vector and by weakening

The alternate hosts, too, have their natural enemies. Sweetfern particularly supports a veritable zoo of defoliators and sapsuck- ing insects. A soft scale was found killing patches of sweetfern in a pine plantation in Michigan. Unfortunately the scale did not kill enough sweetfern stems to curtail the spittlebug. Aphids and leafhoppers are common residents as well. I studied several sweetfern defoliators in an attempt to find a biological control of this host. The sweetfern moth, Acrobasis comptoniella Hülst, is one of the more common ones, and it occasionally defoliates small patches of the host but probably has little effect because

Table 6—/./fe table of mortality for five generations of ttie Saratoga spittlebug on red pine in three Michigan plantations

Number alive at Range of

Age beginning of Mortality Number Percent percent interval interval (per acre) factor dying mortality mortality

Egg

Nymph 1-2

Nymph 3-5

Adult!

39,768

27,620

14,596

13,963

Generation mortality: 64.89% (range: 43.48-98.83) Sex ratio (female:male): 1.00:0.97

Nonviability 325 0.83 0.17-8.27 Parasitism 777 1.95 .16-12.78 Prédation 24 .01 0-.35 Incomplete development 734 1.86 .17-9.27 Incomplete emergence 1,600 4.03 1.44-11.39 Other 8,688 21.86 10.87-47.91

Total 12,148 30.54 23.64-60.49

Desiccation Variable Prédation — — Moderate Other — — Variable

Total 13,024 47.15 8.34-62.82

Prédation Small Disease — — Variable

Total 633 4.34 3.10-34.75

Parasitism (Diptera) 1,030 7.37 1.64-11.95 Other 3,474 2.49 22.90-93.28

Total 4,504 10.86 4.23-94.00

^Adult samples taken before all eggs deposited; mortality would have been higher later in the season from prédation and other factors.

34

sweetfern tends to resprout rapidly. Besides, Acrobasis has at least 16 known parasites that keep its populations in check (Wilson 1970).

Other sweetfem defoliators include the leaf tier, Aroga argutiola Hodges; the sweetfem underwing, Catocala antinympha (Hübner); and the moth Nemoria rubrifrontaria Packard (Wilson 1974, 1975, Wilson and Heaton 1974). None of these are ever numerous enough to be a threat to sweetfem.

Prevention and Control Tactics

Numerous researchers have attempted various tactics to prevent and control spittlebug outbreaks by using cultural, chemical, and other means against the insect or its alternate hosts. Techniques that have been proposed or tried are presented here. A few have proven useless, others are outmoded, and some are of historical value only. Certain approaches, however, show promise for the present and for future spittlebug management programs.

Prevenf/on—Secrest (1944) was the first to suggest that the quantity of alternate host material was important for spittlebug buildup and proposed that trees should not be planted where sweetfem was abundant. Years later, Wilson and others (1977) showed the relative value of sweetfem and other alternate hosts for spittlebug population buildup. Considering that new plantations have small trees and the alternate hosts grow and spread somewhat in the years following planting, fields proposed for planting should have no more than the following paired percentages of sweetfem and other hosts: 0/40, 10/30, 20/10, and 25/5. Higher percentages could support spittlebug populations that might injure the trees. At the above paired percentages, spittlebugs seem not to be able to damage a tree more than lightly. However, if all the sweetfem is in large clumps, pockets of trees may be injured.

Cultural and biological confro/—Cultural methods and biological agents have great potential for reducing spittlebug populations but methods are still unknown. Plowing under and mowing sweetfem were attempted, but in most cases the treatments only stimulated growth of the plants. Site is important for pine and for sweetfem, which seems to do best on the sandier sites marginal for pine.

Closely spaced trees, when growing well, shade out sweetfem. Secrest (1944) suggested planting pines with some hardwoods to give shade because he noticed that spittlebugs were worse in open stands. He felt such mixed stands would have better site quality because of the hardwoods, and the hardwoods would help shade out the sweetfem. This would also encourage certain wildlife.

Researchers have not yet attempted increasing or augmenting parasites, predators, and diseases. Egg and adult parasites seem to be best prospects for control. Adult parasitism in excess of 60

percent by the pipunculid (probably Verrallia virginica) reduced spittlebug population in Wisconsin (Ewan 1961).

Biological control of sweetfem by either defoliators or sapsuck- ing insects so far shows little promise.

Chemical control—The spittlebug became a pest problem concurrently with the development of DDT; consequently, it was one of the first forest insects to be tested and controlled with DDT. In 1943, a year before DDT was tested, Secrest (1944) said that the use of chemicals would be unsatisfactory because the adults were sucking insects and a contact insecticide would be needed. He tried pyrethrin and found that although it would kill spittlebugs in cages, it was useless in the field because the slightest disturbance sent the adults flying away. The arsenicals in vogue during the 1930's were stomach poisons and useless on the spittlebug. Fortuitously, DDT was the "right" insecticide and was used from 1945 to about 1963. It was used in a quantity that qualifies the spittlebug as the most chemically treated forest pest on National Forest System lands in the Northeastern United States (Fowler and others 1986).

Working in Wisconsin in 1944, Anderson (1945b) applied five pesticide formulations, one of which was DDT, to caged spittlebugs on jack pine trees. The cage tests showed relative differences in pesticide toxicity (table 7); the field tests gave similar results at first, but only DDT held up over time. After 8 weeks in the field tests, 89 percent of trees treated with DDT still showed no spittlebugs. Secrest (1946), who made the first aerial spray tests with DDT, used dosages of 0.25, 0.5, 1, and 2 lb/acre in 1 gal of kerosene or fuel oil. The best control was a per acre dosage of 2 lb of DDT in 1 gal of oil. Other dosages were unsatisfactory, except 5 lb in 3 gal of oil. This gave excellent control but was thought excessive. More DDT tests were made by Milliron (1949), who found DDT at 1 and 2 lb/acre gave 98 and 100 percent control after 72 hours. Both dosages seemed satisfactory, but the oil carrier at the 2-lb dosage acted as a herbicide by spotting Rubus plants and causing some leaf fall. Because the 2-lb dosage inadequately controlled Rubus, he recommended the 1-lb dosage for future spray programs.

Table 7—Toxicity of several cliemical insecticides to Saratoga spittlebug adults in cages on treated pine branches'*

Insecticide Cone, of Mortality

(0/0) 24 hr 48 hr

DDT 1.0 96 100 Sabadilla +

hydrated lime 20-80 97 100 Hydrated lime 100 62 91 Bordeaux 4.8 14 32 Lime-sulfur 2.4 9 22

iData taken from Roger F. Anderson. DDT and other insecticides to control the Saratoga spittle insect on jack pine, 1945.

35

As DDT was phased out because of its various undesirable effects, scientists tried to find safer chemicals at lower dosages. Mist-blower tests with 0.5- and 1-lb/gal/acre dosages of malathion were tried, and both dosages controlled more than 99 percent of the spittlebugs (Millers and Wilson 1965). The only problem with malathion was that its effectiveness lasted only about 2 days in the field. Large-scale tests using helicopters followed. These tests proved that malathion by air at 1 Ib/gal/acre was better than 0.5 lb/gal (Wilson and Millers 1966). A low-volume malathion formulation applied at 10 oz/acre was equally good. The latter's major advantage, besides reducing the dosage by one-third, was that its bulk was one-twelfth that of the normal oil-based dosages, so that aircraft could cover many more acres with each load. Large-scale programs in 1969 using malathion (Cythion LV 95 percent) controlled 98 percent of the spittlebugs and proved the value of using low-volume dosages and a safe chemical such as malathion.

1969 (Wilson and Kennedy 1968, 1971). Granular propoxur, aldicarb, carbofiiran, and phorate greatly reduced the nymphs at 0.5 to 3 lb/acre rates, and the suppression was comparable to malathion (tables 8 and 9). Liquid propoxur and carbofuran controlled only at the 2- and 3-lb/acre rates. The other chemicals tested—dimethoate, disulfoton, fenitrothion, and oxydemeton- methyl—were not effective at the formulations and dosages tried. Systemics have not been used in large-scale control programs but should be considered in the future because they can be used 1 to 2 months before adults emerge. Timing is usually planned for early to mid-June to get the third or fourth instars during migration onto sweetfern. Sweetfern requires a week or more to translocate the chemical.

The advent of new and promising pesticides prompted further tests against the adult spittlebug. Satisfactory control resulted in registration of carbaryl and chloropyrifos.

Though malathion was satisfactory, its short residual retention made timing critical. In large control programs, it became difficult to spray precisely after complete adult emergence and before too many eggs were laid. This prompted the testing of systemic chemicals against the nymphs on their alternate hosts. One early test against the nymphs was tried using DDT at 0.5, 1, and 2 Ib/gal/acre. The chemical was applied over jack pine plantations prior to nymphal eclosión in order to kill the young nymphs, but control was poor and most nymphs survived (Bess and Eaton 1948).

The systemic chemical propoxur was tested as a granular formulation to control nymphs in 1966 and 1967 at 0.5, 1, 2, and 3 lb/acre. Control ranged from 97 to 100 percent, suggesting that systemics were effective in combating the spittlebug in the nymphal stages. This success led to further tests in 1968 and

Table S—Toxicity of granular systemic insecticides on Saratoga spittlebug nymphs feeding on sweetfern^

Table 9—Toxicity of mist-blower applications of various systemic insecticides on Saratoga spittlebug nymphs feeding on sweetfern^

Insecticide Application rate

(lb/acre) Percent mortality

Propoxur (5%) Disulfoton (10%) Aldicarb (10%)

Carbofuran (5%)

Phorate (10%)

3 3 3 2 1 0.5

3 2 1 0.5

3 2 1 0.5

100 48

100 100 98 98

100 100 100 98

99 96 92 94

Insecticide Application rate

(lb/acre) Percent mortality

Propoxur (cone.)

Propoxur (diluted 1:5)2

Carbofuran (wp)

Carbofuran flowable (diluted 1:5)

Dimethoate (cone.)

(diluted 1:5)

(wp)

Disulfoton (cone.)

(diluted 1:5)

Fenitrothion (diluted 1:5)

Oxydemeton-methyl (cone.)

3 2 1 0.5

3 2 1 0.5

3 2 1 .05

2 1 0.5

2 1 0.5

2

3

3

2 1 0.5

100 100 92 29

99 98 86 28

100 100 66 41

95 76 66

49

0 0 0

0

0

0

0 0 0

iData taken from Louis F. Wilson and Patrick C. Kennedy, Control of Saratoga spittlebug nymphs with systemic insecticides, 1971.

iData taken from Louis F. Wilson and Patrick C. Kennedy, Control of Saratoga spittlebug nymphs with systemic insecticides, 1971. 2Dilutions—chemicahwater.

36

Herbicida! coníro/—Herbicides have also been tried for controlling the nymphal hosts. Researchers tested 2,4-D on sweetfern in the 1950's and 1960's with generally poor results (North Central Forest Experiment Station file report). Linnane and Osgood (1976b) tried one to three applications of 2,4-D to kill sweetfern and lambkill. The herbicide killed the tops of the plants, but nymphs developed on the stems without apparent harm. One season later, however, 90 to 95 percent of the plants were gone and the nymphal population was down. Apparently, timing for application was not critical and Linnane and Osgood (1976b) recommended treatments from mid-June through July.

Heyd and others (in press) controlled sweetfern with fosamine ammonium and glyphosate in late summer. Fosamine ammonium applied at 1-, 2-, and 3-gal/acre dosages killed the sweetfern,

Table 10—Recov^eAy of sweetfern following herbicidal treatments^

Herbicide Herbicide applied/

acre

but because it was phytotoxic to jack pine, expensive, and did not kill blueberry, it was rejected in favor of glyphosate. Glyphosate at 2 and 3 qt/acre controlled the best, even 3 years after treatment (table 10). Heyd and others (in press) recommended that 2 qt/acre be applied in the late summer because it reduced sweetfern 83 to 100 percent. After 3 years, sweetfern recovery was only 4 percent and part of that was from invasion and edge effect of the plot tests. Recall that spittiebug populations seldom reach destructive levels until 25 to 30 percent of the ground is covered by sweetfern (Kennedy and Wilson 1971).

Hexazinone applied in April or May at 1.5 to 2.0 lb active material/acre has shown some promise in northern Wisconsin. It controlled sweetfern for at least 2 years and probably longer.

Mean percent sweetfern

Pre-treatment 1st yr 2nd yr 3rd yr

Fosamine ammonium

Glyphosate

3 gal 2 gal 1 gal 3 qt 2qt 1 qt

36 32 31 37 31 42

1 5 5 6 4

10

iData taken from Robert L. Heyd et al., Managing Saratoga spittiebug Aphrophora saratogensis (Fitch) in pine plantations by suppressing sweet-fern. Northern Journal of Applied Forestry [In press] '

37

Surveillance

Survey Methods

Young pine plantations need to be monitored for the Saratoga spittlebug until they are beyond risk of injury. Several kinds of surveys are available to forest managers for rating the risk of potential damage and for detecting, evaluating, and suppressing spittlebug populations (Benjamin and Beckwith 1956). Risk of injury, however, begins before the trees are planted because the composition of the alternate hosts on prepared planting sites affects spittlebug survival. Several steps are involved in assessing the influence of the Saratoga spittlebug on the management of proposed pine planting sites or established plantations (fig. 35). Briefly, when there is a threat of spittlebug injury, a proposed planting site or young pine plantation not yet injured should first be rated for potential injury by using the alternate hosts as an index of risk. If such rating indicates low risk, no further action is needed. Moderate or high risk ratings entail a balancing of the cost benefits of various management alternatives before pro- ceeding. The alternatives then are • not to plant trees on a new site or, in plantations beyond

recovery, to bypass treatment prescriptions; • to plant trees on a new site, and/or reduce alternate hosts in

well-stocked plantations; or • to monitor the stand and, if appropriate, control the

spittlebug. Surveillance is involved in all the steps in this process. The various kinds of surveys follow.

Risk

Risk-rating—Prospective pine sites should be risk-rated for potential spittlebug injury before planting (Wilson 1971b, Wilson and Heyd 1978). Established plantations, too, can be risk-rated. Risk-rating should be conducted between May and July so that alternate hosts can be easily identified. The procedure, however, must be completed by mid-June in young plantations so control measures can be applied if needed that year. Note that well- stocked stands of pine taller than 5 m and not yet showing visible spittlebug injury symptoms are safe and need not be risk- rated. Trees over 6 m tall are usually safe at any stocking density. Brood-trees with spittlebugs and adjacent spittlebug-infested stands increase the the probability of spittlebug injury and should be considered when risk-rating a prospective planting site.

There are three risk categories—low, moderate, and high. Low risk means that injury from spitflebugs will not occur or, at most, will be negligible. Moderate risk indicates that spittlebugs could cause some growth loss, light flagging on scattered shoots, and crooked stems on a few trees. High risk indicates that spittlebugs will cause heavy growth loss, many crooked stems, and numerous top-killed or dead trees.

Saratoga spittlebugs cause economic damage only when suitable alternate hosts are abundant. Thus, one must consider the kinds and density of alternate hosts when selecting planting sites or

PROPOSED PLANTING SITE

PLANTATION

LOW RISK -^7

^(+)

HIGH RISK

' MEDIUM RISK

NO

RESTRICTIONS

/-^

UATE \

5T-

FITS A

/^ \

1 EVAL

1 COÍ . .\ BFNF

DO NOT PLANT

PLANTATION BEYOND RECOVERY {+)

PLANT AND/OR REDUCE

ALTERNATE HOSTS

♦ ACCEPT RISK

CONTROL

UNLIKELY

Figure 35—Decision-making guidelines and probable consequences of Saratoga spittlebug management. (See Management Guidelines section for details.)

when determining the risk of injury to young pine stands. Because sweetfem is the most important alternate host, risk- rating is done by estimating and comparing the relative amounts of sweetfem and other suitable nymphal hosts (fig. 36).

38

10 20 30 40 50 60 70 80

PERCENT SWEETEERN

Figure 36—Saraioga spittlebug risk categories based on percent sweetfern compared to percent otiier alternate hosts.

Risk-rating presupposes that a proposed site or plantation has or will have at least 600 trees/acre. Fewer trees increase the risk.

Risk-rate unplanted land between May and July for best results. Risk-rate plantations in May or early June in order to follow up with nymphal surveys. You will need the following equipment: sketch map of the area, instructions and risk-rating form (page 53), clipboard, and pencil. To risk-rate an area proposed for planting pine or an established pine plantation:

1. Draw transect lines on planting sketch or map. Make transects parallel and spaced 2 to 5 chains apart (1 chain = 66 ft or 20 m). Use 5-chain spacing on unplanted land with good visibility; use a spacing as close as 2 chains where the lateral view is inhibited by trees and/or terrain.

2. Walk transects. Stop every 1 to 2 chains to observe the ground cover. First, estimate percent of ground cover occupied by the sweetfern canopy and then the percent occupied by nonhosts (i.e., grasses, sedges, lichens, mosses) and bare ground. Then estimate percent of the other host plants (all other broadleaf herbs, ferns, small trees, etc.) or calculate this percent by subtracting the percent sweetfern and percent nonhosts from 100 percent.

3. Use risk-rating triangle to determine if risk is low, moderate, or high at each stop. Plot the percentage of sweetfern against the percentage of other hosts on the triangular graph on the form (fig. 36). The point where the

coordinates intercept on the graph indicates the risk class for the area rated.

For example, if you plot 10 percent sweetfern against 20 percent other hosts, the risk given by the graph is low. If, however, you plot 30 percent sweetfern against 30 percent other hosts, the risk is high.

Place an L, M, or H at each stop to indicate low, moderate, or high risk, respectively. While walking transects, observe and note any changes in overall ground cover so that you can draw boundaries between areas of different risk. This is especially important for sweetfern, which has a tendency to form large clumps. If you have difficulty distinguishing a risk category (e.g., moderate from high), favor the greater risk.

4. After completing all observations, draw lines on the sketch or map that enclose areas of similar risk (fig. 37).

5. Estimate the acreage in each risk category.

6. See Management Guidelines (page 44) to formulate a plan of action.

Aerial fî/sIc-Rai/ng—Risk-rating prospective plantings and plantations is particularly easy and cost effective with a helicopter when many acres need assessing or time is especially short. A person experienced with the ground risk-rafing procedure can do an aerial survey over the same area in minutes.

H H / M M

H H y M j r^

H /M M/ L

H y M > ̂ L L

M r^ L L

M

M '^^

L L

V M M ^

Figure 37—Sample risk-rating map delineating areas of similar risk.

39

Low-risk areas are readily distinguishable from moderate- and high-risk areas, and the observer gains an excellent perspective of the amount and distribution of different risk zones. Aerial risk-rating is also an excellent way to screen sites rapidly and determine whether ground checks are needed. To risk-rate by

1. Assign areas to low-, moderate-, or high-risk categories. You may have to rely mostly on the amount of sweetfern as the principal component of the ground cover. The risk is low when sweetfern makes up less than 15 percent, moderate when it makes up 15 to 25 percent, and high when it makes up more than 25 percent of the vegetation.

2. Draw boundaries of the categories on the sketch map provided on the Risk-rating Survey Field Form.

3. Determine the acreage in each category.

4. Refer to the Management Guidelines (page 44) to formulate a plan of action.

Detection

Detection survey—The purpose of a detection survey is to learn whether the Saratoga spittlebug or its damage is present at any particular time or place. It can be made casually or systematically, whichever the observer desires. It is usually a ground survey, but it can be made from the air when the infestation is sufficiently heavy to show gross symptoms such as nagging, topkill, or dead trees (table 11). Ground checks, however, may also be needed to verify the insect's presence, because a few other insects and some diseases such as scleroder- ris canker cause similar gross symptoms of damage.

To make a Saratoga spittlebug detection survey from the ground, you will need a knife, vials, and an insect sweep net—a collect- ing net with a muslin bag instead of the typical net bag. To take a detection survey:

1. Detect damage. Look for gross symptoms of spittlebug damage such as flagging (reddish shoot tips), topkill, or dead trees. These are present only in moderate to heavy infestations (cover photo). Table 11 gives the various gross symptoms from spittlebug feeding and their ease of detection.

2. Detect injury. Examine 1-year-old shoots for feeding wounds and scars (any time of year). You will need to scrape off the bark of the shoot with a knife or other sharp blade to see these injuries (cover photo).

3. Detect eggs. Search for eggs (August through the following April only). Examine the leader or top whorl buds. You can feel or see the eggs as bumps on the surface or see them protruding from the bud scales (fig. 14).

4. Detect nymphs. Search for spittlemasses and nymphs (mid-May through early July only). The nymphs will be inside the spittlemasses at the bases of sweetfern and other ground cover plants (back cover photo).

5. Detect adults. Search for adults (mid-July through August only). Use an insect sweep net and sample one or several trees for adults. Run the net up the foliage, and, at the end of the swing, flip the end of the net over the ring to close the bag. You may need to catch the adults in a bottle or vial to identify them because they may fly away when the bag is opened.

Table 11 —Progression, ease of detection, and feeding intensity needed to produce gross symptoms of spittlebug damage to red pine

Damage symptoms

Slight uneven reduction in lateral shoot elongation

Barely perceptible yellowing of foliage on 2-year-old growth of lateral branches

Dead shoots Foliage yellow to red

(flagging) Stunting

Dead branches, tops, and trees

Crooked and misshaped trees

Ease of detection

Detected only by careful lateral-terminal growth measurements

Difficult to detect even with normal foliage for comparison

Easily detected, mostly on upper part of tree

Easily detected, generally occurs in clusters, with abundant alternate hosts

Seasons

Summer

Fall-winter

Spring-summer

Spring-summer

Feeding intensity needed preceding

symptoms

2 or more years of light to moderate feeding

1 or 2 years of moderate to heavy feeding

2 or 3 years of heavy feeding

3 or more years of heavy feeding

40

You may stop the survey after step 2, 3, 4, or 5 if the feeding injury or the insect is collected and verified. Note that when infestations are too light to show injury, you may need to sample several trees or alternate hosts before locating the spittlebug.

Aerial detection survey—When damage is pronounced, detection also can be made by helicopter or from small-scale aerial color photographs. Ground checks should be made, nevertheless, to verify the insect. Infrared photographic detection prior to visible injury has been tried but found wanting (Latham and Millers 1970).

Evaluation

Feeding scar appraisai survey—This survey estimates the severity of adult feeding, which in turn predicts whether a more detailed nymphal survey should be made the next season. The survey is usually made in fall, after spittlebug feeding, but it can be made in winter or early spring. This is a good way to monitor the population without investing a lot of time and effort. For this survey you will need a sketch map of the area, a knife, a pencil, and a clipboard. Also, because this is a sticky job, you may wish to carry some rubbing alcohol and a cloth to clean your knife and hands. To make a feeding scar survey:

1. Sample only areas with moderate or high risk. (See risk- rating survey, page 53.)

2. Determine the number of samples you will take according to the following acres at risk:

Acres <11

11-20 21-50 >50

Samples needed 20 25 30 35 or more

3. Conduct the survey systematically by walking and sampling at some reasonable interval such as every chain (66 ft or 20 m), tenth row, etc. Plot sample points on a map of the area ahead of time. The idea is to get good coverage of moderate- and high-risk areas and to do it economically.

4. Select an average tree at each sample point.

5. Select a branch from the upper half of the tree and cut a 4-inch section from the center of the 2-year-old growth (the penultimate internode).

6. Scrape off the bark of the 4-inch sample with a knife and count and record the number of scars (red flecks) on the wood (front cover). Mark each scar with an indelible pencil or felt pen to prevent missing or recounting scars.

7. Repeat sampling until all counts have been made and recorded.

8. Average the number of scar counts from the samples. If the average is less than 25, the stand is still safe (with a chance of 9 of 10 times), and a nymphal survey is not required the next season. If the average scar count is between 20 and 25, the area should be scar-surveyed again the next year. If the average scar count is greater than 25, the stand should be surveyed for nymphs in the spring (Nymphal Appraisal Survey, below).

Nymplial appraisai survey—A survey of spittlebug nymphs determines the current threat of injury. Damage in terms of growth loss, deformity, and tree mortality is estimated from the number of spittlebug nymphs relative to the number and size of trees in a stand. Begin looking for nymphs in spittlemasses the second week of June and not later than the third week. Tally the nymphs when most are late instars (third to fifth instars). Younger nymphs are difficult to find and late instars more accurately reflect the adult population that injures the trees. The first four nymphal instars are black and red; fifth instars are chestnut brown. When you find a few of the brown nymphs, it is time to survey.

If the current threat does not warrant concern, nothing further needs to be done that year. However, nymphal surveys should then be scheduled periodically until the trees are 15 ft (5 m) tall or their crowns close, whichever comes first.

For a nymphal survey you will need a sketch map of the planting with risk areas delineated (from Risk-Radng Field Form, page 53), clipboard and pencil, four flags or stakes, a measuring pole (in feet), a square sampling frame 25 in by 25 in (inside measure), and the insect evaluation instructions and the Nymphal Survey Form (page 55). To take a nymphal appraisal survey:

1. First survey the areas of high risk on the risk-rating map. If some areas qualify for control, then survey moderate- risk areas also.

2. Select the number of 1/10-acre sample plots needed depending on plantation size.

No. of plots Acres in high risk 1 1-5 2 6-10 3 11-20 4 21-40 5 40 +

3. Establish 1/10-acre sample plot (66 by 66 fl), demarcating the four corners with flags or posts. Pace off the plot or use a 66-ft tape or rope.

4. Count the number of trees in the sample plot.

5. Determine the average number of whorls per tree. If the trees are the same age, you can determine this easily from five trees.

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6. Measure height (to nearest half foot) of 10 trees scattered throughout the plot. Then determine their average height.

7. Calculate and record the tree-units for the plot by multiplying the number of trees by the average number of whorls by the average tree height.

8. Count the number of nymphs in 50 one-tenth milacre samples using the 25-in by 25-in sampling frame. Begin at one corner of the plot and proceed systematically along the rows of trees. Take samples about 5 or 6 ft apart to get 50 samples evenly spaced throughout the plot. Regularly stagger the sampling locations so that some are taken in the lane between rows and others are taken close to the trees.

9. At each sample location, drop the frame, being sure not to preselect or omit specific plants as you locate the sample. Carefully examine all host plants for nymphs, which will be in spittlemasses at their bases. When you find one live nymph, stop sampling and record the sample as a plus (+). If no nymphs are found after examining all host plants, record the sample as a negative (—). Move to next sample and repeat.

10. Afler taking 50 samples, count the pluses (-\-) and multiply by 2 to determine the percent samples infested with nymphs. The percent samples infested provides an estimate of the number of nymphs for the 1/10-acre plot. Calculate and record the nymphs per tree-unit by taking the number of nymphs per plot and dividing by the number of tree- units per plot. The nymphs per tree-unit gives the potential damage level. (See tables 12 and 13.)

Table 13—Key to action recommended after nymphal appraisal survey'^

Oa. Nymphs/tree-unit less than 1.0—see no. 1 Ob. Nymphs/tree-unit 1.0 or more—see no. 8

1a. Trees shorter than 10 ft—see no. 2 1b. Trees 10 ft or taller—see no. 4

2a. Nymphs/tree-unit less than 0.15—evaluate again in 3 years 2b. Nymphs/tree-unit 0.15 or more—see no. 3

3a. Nymphs/tree-unit more than 0.25—evaluate next year 3b. Nymphs/tree-unit 0.15 to 0.25—evaluate in 2 years

4a. Trees from 10 to 12 ft—see no. 5 4b. Trees taller than 12 ft—see no. 7

5a. Nymphs/tree-unit more than 0.15—see no. 6 5b. Nymphs/tree-unit 0.15 or less—no need to reevaluate

6a. Nymphs/tree-unit more than 0.25—evaluate next year 6b. Nymphs/tree-unit 0.15 to 0.25—evaluate in 2 years

7a. Nymphs/tree-unit more than 0.40—reevaluate next year 7b. Nymphs/tree-unit 0.40 or less—no need to reevaluate

8a. Nymphs/tree-unit 1.0 to 2.0—if there is flagging or noticeable degradation, control this year; if not, reevaluate next year

8b. Nymphs/tree-unit more than 2.0—control this year

■"Given near threshold values, use indicators of the previous year's feeding injury to help nnake a control decision. The previous year's feeding scars persist to add to the present year's injury; thus, use presence of feeding scars, flagging, and the previous insect evaluation, if available, to decide if control is warranted.

Suppression

Table 12—Damage level categories for adult spittlebug feeding

. . K. u IX x Potential growth Damage level Nymphs/tree unit reduction (o/o)

Very /ow—lateral terminal growth differences 0.25 2

Low—up to 4 yr of growth reduction 0.50 6

/Woderafe—up to 10 yr of growth reduction, scattered flagging, some degradation 1.00 25

H/g/7—whole-branch flagging, dead tops, extensive degradation, some dead trees 2.00 41

Very high—óeaó tops, extensive degradation, many dead trees 6.00 66

Predicting control date—Adult spray programs are usually timed so that the chemical is applied when about 80 percent of the adults have emerged. Though this occurs in July, temperatures are sufficiently variable to make the control date vary over a 2-week period from year to year. Timing is especially critical with chemicals that have short residual lives. Spray programs usually begin in southernmost areas and proceed northwards because emergence usually varies a few days from south to north. Predicting control dates from nymphal development is not reliable, so the standard way of predicting the date is by actually observing adult transformation. You will need one or several open-ended rearing cages for this exercise. (A description of a simple, inexpensive cage follows on page 43. ) To predict the control date:

1. In late June select a large sweetfem plant in the open that has one or more spittlemasses with numerous nymphs.

2. Count the nymphs in the spittlemass(es). You'll want about 40 insects, so either add nymphs to the spittlemass from others nearby, or plan to set up enough cages to total 40 or more nymphs.

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3. Set up the cage (instructions follow) over the sweetfern plant.

4. Each morning examine the cage for adult spittlebugs—Û\e,y usually sit on the walls of the cage. Remove the adults and keep a running tally of the number that have emerged.

5. Remove adults daily until half the nymphs have emerged.

6. Begin control spraying about 3 days later. If temperatures have been especially warm, 2 days later is the best predicted date; if especially cool, 4 days later is the best date.

A simple cage, useful for determining when spittlebugs transform, is easy to build, collapsible, readily portable, com- pact, and inexpensive (Wilson 1971a) (fig. 38). The cage is made of plastic window screen and the dimensions are 36 in high (cage opened on top) by 16 in on a side. The walls are supported by four pointed wooden stakes 0.5 in square by 28 in long that protrude 4 in beyond the bottom edges of the cage. Ordinary staples from a staple-gun hold the netting on the stakes. The comer seam of the netting is sewn by hand or machine with plastic thread. The cage can be built to various dimensions.

Figure 3B—Rearing cage for adult Saratoga spittlebugs shown both in position over a sweetfern plant and rolled up for transport and storage.

In use, the stakes are driven into the ground around the plant and the top is folded in and over to resemble the top of a paper milk carton (fig. 38). Four medium binder clips secure the top. Lx)ose soil is packed around the base of the cage on the edge of the netting to make the cage escape proof. When not in use, the cage lies flat and can be rolled up tightly to store or transport (fig. 38).

Pre- and post-control appraisal survey—The efficacy of a chemical control treatment can be assessed by counting populations of adult spittlebugs 1 to 2 days before and 1 to 2 days after treatment. The survey is most reliable if the counts are taken by the same observer at about the same time of day. The survey requires only a sturdy insect sweep net, pencil, and notebook. To take one of these surveys:

1. Set up transects in the plantation and plan to take at least 100 sweep-net samples throughout.

2. Select trees to be sampled and sweep each tree once with the sweep net, quickly moving the net upwards along the tree's foliage from the lowest branch to as high as you can reach.

3. Count and record adults captured after each sweep. If the population is low, you may be able to make several sweeps before counting.

4. Empty the net and repeat sampling along the transects until all samples are taken.

The effectiveness of the treatment can then be determined by in- serting the sweep counts in the following formula:

percent control =

No. of bugs pre-sweep - No. of bugs post-sweep

No. of bugs pre-sweep X 100.

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Management

Management Guidelines

The Saratoga spittlebug can be managed by preventive, cultural, and chemical measures. It can also be managed by doing nothing—that is, by letting an infestation run its course.

Prevention involves restricting the planting of spittlebug- susceptible pines to only no-risk or low-risk areas. This may mean not planting an entire area or omitting just a few small islands or pockets where the important alternate hosts pre- dominate. Not planting a small portion of an area may greatly enhance esthetic and/or wildlife values in some regions. Pockets with 35 percent or more of the ground cover in sweetfern are especially troublesome, and if planted and then infested, there is a nearly certain probability of high injury without control. Even if not injured greatly by spittlebugs, trees in such areas usually grow slowly until their crowns close because of direct competition from sweetfern.

Cultural control mainly involves reducing the principal alternate hosts—especially sweetfern. Deep plowing disrupts and buries sweetfern and usually curtails rapid regeneration. However, deep plowing can disrupt soil structure and water-holding capacity of the plowed soil layer, which may cause a critical situation in sandy soils. Shallow plowing or mowing stimulates sweetfern growth and should be avoided unless repeated for 2 to 3 years, which may be prohibitively costly. Chemical herbicides seldom disturb the soil and provide what appears to be the most reasonable method of reducing ground vegetation. Herbicides suppress sweetfern, brambles, and certain other alternate hosts when applied properly and seem to provide long-term suppression, which will benefit future crops.

Pesticides kill nymphs and adults, but control is usually directed against the adults. This means that pesticides must be applied precisely between adult emergence and egg laying (usually early July). In high-risk areas, two or three applications may be needed before the trees outgrow the risk. The nymphal evaluation survey provides the most accurate predictor of adult population and injury and is recommended for making management decisions.

certain circumstances it can have a positive effect on the forest ecosystem. A spittlebug outbreak used wisely can help land management in a manner similar to the use of prescribed burn- ing. This does not mean that an outbreak should purposely be initiated but rather that an existing outbreak can be allowed to run its course when its effects are deemed advantageous to forest management. What is suggested is a change in thinking, from "all insects are bad and must be suppressed vigorously" to "let's evaluate the situation and capitalize on it if possible."

In practice, spittlebug management is basically a concern of economists because it involves social and economic considerations. It is the economists' job to describe the effects of the insect in socioeconomic terms useful as decision-making criteria for land managers. Such an economic analysis can be found in the section Selecting a Management Strategy. Here, however it is useful to point out how some of the effects of the spittlebug might relate positively or negatively to land management goals under a multiple-use concept.

Timber—Pines are managed primarily for wood products, so the spittlebug is essentially an economic pest. Spittlebugs kill and deform young pines growing in high stress areas where there is abundant sweetfern. These areas often have indices for red pine near or below 50. The better (without sweetfern) areas may have site indices 60 or higher. Manthy and others (1964) showed that well-stocked red pine stands of site index 60 will return financial yields for pulpwood rotations from about 2 to 5 percent and for sawlog rotations from 3 to 7 percent. In contrast, the trees with a site index of 50 can expect a financial yield of less than 3 percent for pulpwood rotations and from 3 to 5 percent for sawlog rotations, and then only if appropriate stocking is maintained. Sometimes less than one-third of the original trees remain in sweetfern pockets after an outbreak, and surviving trees are deformed and unevenly dispersed over the area. Merchantable volume then would yield less than 1 percent on these sites and would certainly not be worthy of additional forest management input as far as forest products are concerned. In areas where the spittlebug does less injury, an economic analysis should be conducted to help decide management practices.

Socioeconomic Considerations

Land managers are concerned with satisfying human needs relative to available natural resources; their goals are to supply wood, water, forage, wildlife, and recreational opportunities.

The Saratoga spittlebug, like most other forest pests, is usually thought of as a deterrent to the achievement of one or more of these management goals because it appears to cause a negative effect on the forest and associated land. Consequently, spittlebugs have historically been evaluated in terms of adverse impact rather than in terms of their effect on land-use goals. The spittlebug need not always be perceived as destructive, for under

From the current viewpoint of the land manager, the spittlebug has a negative effect on the financial yield of pine. Large low- quality sites or extensive sweetfern pockets sometimes might better be left unplanted in the first place and thus be available for other more productive uses. Sweetfern sites, of course, can be planted, but losses should be anticipated and planned for in the overall management objective.

Wildlife—Most plantations, especially red pine plantations, provide little variety and hence are generally unfavorable as a long- term habitat for edge wildlife species such as deer, bear, hare, and grouse. The early stages of a plantation briefly provide some habitat for some edge wildlife.

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Mature red pine stands are generally favorable for interior wildlife species such as squirrels, owls, and warblers (Ohmann and others 1978). Kirtland's warbler is an endangered species that requires young jack pine stands for nesting.

Openings in large pine stands, if properly managed and kept open for several years, can provide forbs, grasses, and shrubs that supply food, nesting sites, and shelter for edge wildlife. Tubbs and Verme (1972) and Ohmann and others (1978) recommended that wildlife openings be established in large stands, and McCaffery (1970) suggested that red pine not occupy more than 30 percent of an area. The best places to create openings in a stand or leave openings during planting are excessively or poorly drained soils, on shallow soils, and in frost pockets (Tubbs and Verme 1972). These areas have little advance reproduction and are the easiest areas to maintain as openings. Tubbs and Verme (1972) also recommended that the openings border trails and other timber types to provide a variety of vegetation and allow escape cover. Openings 1 to 10 acres in size are best, and many smaller areas are preferred over a few large ones. Irregular shapes provide longer perimeters and thus more edge vegetation and are esthetically more pleasing.

Large pockets of sweetfern fit the criteria suggested above for wildlife openings. As trees die on these sites, irregular openings appear that favor the edge wildlife species. Small clumps of remaining pines provide ideal escape cover. Such sites can be managed to remain in the forb-grass-brush stage for many years. And, if such areas are identified prior to planting, they can be left unplanted and managed exclusively for wildlife.

The spittlebug then, can have a strong positive effect on development of edge wildlife habitat. Many of the edge species are also game species, so that proper management also enhances recreational opportunities.

Water yield and quality—Fines have relatively high évapotranspiration and respiration losses, and thinning dense pine stands usually increases water yield (Urie 1971). Thus, areas with trees killed by spittlebugs should have greater water yield, but because these areas usually occupy only a few acres, the increase would be small. Also, any changes would be for only a short duration because shrubs, grasses, and other vegetation will eventually compensate for the pines and trap as much or more water.

Spittlebug-injured trees should not normally affect stream sedimentation and nutrient enrichment from waste products. Because of the highly permeable soils characteristic of most pine plantations, water quality could be affected if a pesticide were used against the insect, and especially so if treated areas were adjacent to streams or lakes. The effect and duration of water quality change would largely depend on the type and amount of pesticide applied. At least in northern areas, the spittlebug ap-

pears to have little or no long-term effect on water yield and quality and only a slight short-term positive or negative effect under conditions of extensive stand change.

Recreation and visual quality—Most pines become more esthetically pleasing as they age. The spittlebug seldom injures trees more than 5 m tall. Young dying, dead, and deformed trees are not esthetically pleasing. When someone encounters a spittlebug-injured stand, reaction varies from non-interest to excitement or concern. Concern is often about the welfare of the trees, and the level of excitement depends on the degree of injury and on the ownership of the trees. Hunting opportunities may improve from the change in edge wildlife habitat following a spittlebug outbreak. Fishing will probably not change unless water quality changes due to silting or pesticide contamination.

Selecting a Management Strategy

After risk-rating an unplanted area or pine plantation, decide whether ftirther evaluations are needed. If the risk is low, the potential damage is also low and ftirther evaluation is un- necessary. If the risk is moderate or high, however, further evaluations, decisions, and actions are warranted (fig. 35).

Unplanted sites—On unplanted land that has been risk-rated as moderate or high, you have the option to plant and accept the risk, plant and monitor the insect and control a threatening population, plant and reduce the alternate hosts for long-term control of the spittlebug, or not to plant. To select an economically sound strategy, a cost-benefit analysis should be made. That is, the costs of each strategy should be carefully weighed against the benefits, and then a strategy should be selected that provides an acceptable return on investment.

More specifically, the present value of returns (PVR) should be compared to the present value of costs (PVC) to derive the net present value (NPV) of a particular management strategy (NPV = PVR - PVC). This is done by discounting projected costs and returns at the desired rate over the period in which each cost or return is to be realized. If the resulting new present value is greater than or equal to zero (PVR > PVC), the management strategy in question produces or exceeds the desired return on dollars invested. In addition, the size of the positive net present value indicates additional dollars that can be spent now, yet still achieve the given return. A negative net present value means the management strategy does not provide the desired return on investment. Again, the size of the net present value represents the dollar amount in present money (money that can be spent now) with which a project either falls short of (-NPV) or exceeds (+NPV) the desired return on investment.

An example of the costs and returns (on a per acre basis) of managing a stand using a 60-year rotation with two thinnings is shown in table 14.

45

Table 14—Costs and returns of managing a hypothetical red pine stand using a 60-year rotation with two thinnings

Year Operation Cost/acre Return/acre

1 Stand establishment $120 5 Spittlebug control 12 —

10 Spittlebug control 12 — 35 Thinning — $140 45 Thinning — $400 60 Final harvest — $1200

In the example in table 14, the

present value of costs =

120 + 112(1 +iy ^ 12 (1 + ¿y' (1 + ry

present value of returns =

(1 + ry

140 (1 + ty^ _^ 400 (1 + ty^ _^ 1200 (i + ty^ (1 + r)35 (1 + r)45 (1 + r)6o

Where: r = desired rate to be earned as a decimal (e.g., 0.07 for 7

percent); / = rate above inflation expected for costs or returns. For

example, forest products may increase in value faster than inflation. So, / for PVR may be set at 0.04 if a 4-percent increase above inflation is expected.

net present value = present value of returns — present value of costs.

If there is a positive NPV, the management strategy pays at rate r; the size of the value is money that can be spent now and still earn rate r.

If there is a negative NPV, the management strategy does not pay at rate r.

An example of using net present value (NPV) to select the best management strategy follows:

Let's assume that we want to plant an area to red pine and that this acreage has significant portions in the moderate- and high- risk categories for Saratoga spittlebug. We want to plant 600 trees per acre to be harvested at age 45. For the purpose of this example, we set establishment cost at $116.72 per acre (Olson and others 1978). Any additional costs and returns expected will depend on the management strategy selected.

Table 15 presents the net present values resulting from different management strategies for site indices of 50, 60, and 70. The yield in cords of each management strategy in the table is used to determine stumpage price (i.e., stumpage price per acre +

6.44 -\- (0.36 X no. cords harvested)). The upper and lower limits of growth loss in a moderate-risk area are 4 and 10 years, respectively. Growth loss caused by the Saratoga spittlebug uniformly affects the productivity of the entire tree, so that height and diameter growth are reduced. Thus, reduced yields from growth loss were calculated by using the volume yields of a rotation shortened by the years of lost growth. For example, given 4 years' growth loss, the yield of this planting would be calculated for age 41 instead of 45.

It is apparent (table 15) that accepting the risk of injury is not an option for high-risk areas or for moderate-risk areas of site index 50 or less at the selected rates. The monitor and spray strategy consistently produces the highest return. Reducing alternate hosts is a much more expensive operation, yet it provides greater NPV's in most instances than accepting the risk. The only exceptions shown in table 15 are for rates 8 to 9 percent in moderate risk (lower limit) on site index 70. However, any increase in productivity of the site from reducing ground cover competition was not considered because of a lack of yield data for site indices greater than 70. The net present values for site indices 50 and 60 include an increase in yield reflecting a release from ground cover competition. This is shown most dramatically in the high-risk areas with site indices of 50 and 60. Here, reducing alternate hosts yields higher NPV's than monitoring and spraying.

Reducing alternate hosts provides protection for future crops. Thus, monitoring, surveying, and spraying may produce higher returns for the present rotation; however, future plantings can still derive the benefits of reducing alternate hosts.

P/anfaf/ons—Basically, the same procedure to make management decisions for proposed planting sites is used in established pine plantations. The present value of returns is calculated by discounting the value of the crop at maturity by the number of years to maturity at the desired interest rate. The present value of returns (PVR) is then compared to the present value of costs (PVC) for each management strategy (and any other costs to be incurred) to calculate net present value (NPV). If the spittlebug deforms, kills, or slows the growth of the trees, the value of the crop at maturity is modified by the reduced yield caused by these injuries.

If monitoring and control is chosen as the best management strategy, a spittlebug nymphal appraisal survey should be scheduled. Injury in terms of growth loss, deformity, and dead trees is estimated from the number of spittlebug nymphs relative to the number and size of trees in a stand. (See Nymphal Ap- praisal Survey.) Control of the adult spittlebug is then recommended on the basis of this survey.

If the current threat does not warrant concern, nothing further needs to be done that year. Surveys, however, should be scheduled periodically until the trees are taller than 15 feet (5 m) or their crowns close, whichever comes first.

46

Table 15—A/ef present values at four discount rate percents for different management strategies and site indexes on planting sites with moderate and high risk for Saratoga spittlebug (the proposed planting is 600 red pine per acre to be harvested at age 45)

Net present value ($/acre) at discount rate percent

Moderate risk High risk

Management strategy 70/0 8% 90/0 10% 7% 8% 90/0 10%

Site Index 70 Accept risk (lower limit)^ $246 122 41 -12 — — — — Accept risk (upper limit)2 216 83 3 -44 -117 -117 -117 -117 Reduce alternate hosts^ 265 114 15 -49 265 114 15 -49 Monitor and spraye 314 164 66 1 307 157 59 -5 No risks 325 174 75 11 325 174 75 11

Site Index 60 Accept risk (lower limit) 89 19 -27 -58 — — — — Accept risk (upper limit) 81 2 -45 -73 -117 -117 -117 -117 Reduce alternate hosts 132 27 -42 -88 178 57 -23 -74 Monitor and spray 136 46 -12 -50 128 39 -19 -57

No risk 146 56 -2 -41 146 56 -2 -41

Site Index 50 Accept risk (lower limit) -10 -47 -70 -86 — — — — Accept risk (upper limit) -6 -50 -77 -92 -117 -117 -117 -117 Reduce alternate hosts 1 -60 -100 -126 32 -39 -86 -117 Monitor and spray 14 -35 -67 -88 7 -42 -73 -93 No risk 31 -19 -52 -74 31 -19 -53 -74

1 Moderate risk (lower limit) = 4 years lost growth.

2Moderate risk (upper limit) = 10 years lost growth. However, yield at 45 years was discounted to age 55 because loss of 10 years growth at age 45 reduced yield below acceptable limits. High risk = total loss.

3Cost = $60/acre; reducing alternate hosts increased site index by 5 for moderate-risk areas and 10 for high-risk areas for site indexes 50 and 60. No data were available for yields on site indices greater than 70.

sSpray cost—$12/acre for aerial application. Moderate risk areas were evaluated three times and sprayed once. High-risk areas were evaluated three times and sprayed twice. If site index is <50 add one evaluation and one spray to account for increased length of spittlebug-susceptible height stage (3 to 15 ft) due to slow growth.

sYield expected with no threat of loss or need to control, presented for comparison.

Christmas trees—Scotch pine or Austrian pine Christmas trees are vulnerable to Saratoga spittlebug injury when alternate hosts are abundant. Christmas tree stands should be kept free of sweet fern and other primary alternate hosts as much as possible to prevent injury. Even clean-looking stands occasionally have abundant small forbs such as orange hawkweed, which can sup-

port enough spittlebugs to cause some flagging. Red pine, if grown for Christmas trees, is very vulnerable to attack; eastern white pine, however, is nearly resistant to injury even if mixed with other tree species. The cost of prevention and control in Christmas tree plantings is economically justified when needed.

47

Literature Cited

Anderson, G. W. Sweet-fern rust on hard pines. For. Pest. Leafl. 79. Washington, DC: U.S. Department of Agriculture, Forest Service; 1963. 4 p.

Anderson, N. A.; French, D. W. Sweet-fern rust on jack pine. Journal of Forestry 62:467-471; 1964.

Anderson, Roger F. Biology of the Saratoga spittle insect. Washington, DC: U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine; 1945a. 21 p.

Anderson, Roger F. DDT and other insecticides to control the Saratoga spittle insect on jack pine. Journal of Economic En- tomology 38(5):564-506; 1945b.

Anderson, Roger F. Saratoga spittlebug injury to pine. Journal of Economic Entomology 40(l):26-33; 1947a.

Anderson, Roger F. The Saratoga spittlebug. Journal of Economic Entomology 40(5):695-701; 1947b.

Ball, E. D. Notes on the Cercopidae of America north of Mex- ico (Homoptera). Entomological News 39(2):4-49; 1928.

Ball, E. D. The spittle insects of the genus Aphrophora occurring in the United States (Homoptera: Cercopidae). En- tomological News 45(7)175-179; 1934.

Doering, Kathleen C. Synopsis of the family Cercopidae (Homoptera) in North America. Journal of the Kansas En- tomological Society 3(3-4):53-64, 81-108; 1930.

Doering, Kathleen C. Some biological notes on the Cercopidae north of Mexico (Homoptera). Journal of the Kansas En- tomological Society 4(2):48-51; 1931.

Doering, Kathleen C. A revision of two genera of North American Cercopidae (Homoptera). Journal of the Kansas En- tomological Society 14(4): 109-134; 1941.

Doering, Kathleen C. Host plant records of Cercopidae in North America, north of Mexico (Homoptera). Journal of the Kansas Entomological Society 15(2):65-72, (15)3:73-92; 1942.

Eaton, Charles B. The Saratoga spittlebug. For. Pest Leafl. 3. Washington, DC: U.S. Department of Agriculture, Forest Ser- vice; 1955. 4 p.

Ewan, Herbert G. The Saratoga spittlebug Aphrophora saratogensis (Fitch), a study of gradients of feeding injury distribution on red pine, Pinus resinosa Ait., and notes on the diapausing egg. Spec. Rep. M-1. Milwaukee, WI: U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine; 1953. 36 p.

Benjamin, Daniel M.; Beckwith, Leroy C. An evaluation of Saratoga spittlebug population estimation techniques. In: Pro- ceedings, 11th annual meeting. North Central Branch, En- tomological Society of America; 1956 March 28-30; Lafayette, IN: Purdue University; 1956: 19-20.

Benjamin, Daniel M.; Batzer, Harold O.; Ewan, Herbert G. The lateral-terminal elongation growth ratio of red pine as an index of Saratoga spittlebug injury. Journal of Forestry 51(ll):822-823; 1953.

Ewan, H. G. Some effects of temperature extremes on Saratoga spittlebug populations. Tech. Note 519. St. Paul, MN: U.S. Department of Agriculture, Forest Service, Lake States Forest Experiment Station; 1958a. 2 p.

Ewan, Herbert G. The use of the host size and density factor in appraising the damage potential of a plantation insect. In: Proceedings, 10th International Congress of Entomology; 1956 August 17-25; Montreal. Ottawa: Mortimer, Ltd.; 1958b: 363-367.

Bess, Henry A.; Eaton, Charles B. Airplane spraying experiment with Saratoga spittlebug, 1947. Rep. For. Insect Lab. Milwaukee, WI: U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine; 1948. 4 p.

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Gruenhagen, R. H.; Riker, A. J.; Richards, C. Audrey. Burn blight of jack and red pine following spittle insect attack. Phytopathology 37:757-772; 1947.

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51

Field Survey Forms

Use the following forms for:

1. Risk-rating Saratoga spittlebug 2. Nymphal appraisal survey of Saratoga spittlebug

Before risk-rating and sampling, read the section entitled Risk (page 38 of this publication). Photocopy the forms (front and back) for field use.

52

Saratoga Spittlebug Risk-Rating Survey

Field or Pianation No Date

County T R.

Total acreage.

_S._

RISK-RATING

A Sweetfern B Other hosts C Nonhosts & bare ground

A % % B % % C % %

100% 100%

A % % B % % C % %

100% 100%

A % % B % % C % %

100% 100%

A % % B % % C % %

100% 100%

A % % B % % C % %

100% 100%

A % % B % % C % %

100% 100%

A % % B % % C % %

100% 100%

100%

100%

100%

100%

100%

100%

100%

Total

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

0 10 20 30 40 50 60 70 80 90 100

PERCENT SWEET-FERN

Use grid below to sketch planting

Acreage in each risk category:

low moderate high _

53

Instructions for Saratoga Spittlebug Risk-Rating Survey

Unplanted land should be risk-rated between May and July for best results. Plantations should be risk-rated in May or early June so that nymphal surveys can be taken in June. Well-stocked stands of pine (that is, 600 or more trees/acre) taller than 3 m and with no visible symptoms of spittlebug injury are safe and need not be risk-rated. To risk-rate, you'll need a sketch map of the area, a clipboard, and a pencil. If this is an aerial survey, also read the instructions for risk-rating by air.

Risk-rating on the ground Risk-rating by air

Draw transect lines on planting sketch or map. Make transects parallel and spaced 2 to 5 chains apart (1 chain = 66 ft. = 20 m). Use 5-chain spacing for unplanted land with good visibility; use a spacing as close as 2 chains if the lateral view is inhibited by trees and/or terrain.

Walk transects. Stop every 1 to 2 chains to observe the ground cover. First, estimate the percentage of ground cover occupied by sweetfem foliage and then the percentage occupied by nonhosts (that is, grasses, sedges, lichens, mosses) and bare ground. Then estimate the percentage of the other host plants (all other broadleaf herbs, ferns, small trees, etc.) or calculate this percent by subtracting the percentage of sweetfem and percentage of nonhosts from 100 percent.

1. Estimate the low-, moderate-, and high-risk categories. You may have to rely mostly on the amount of sweetfem as the principal component. The risk is low for less than 15 percent sweetfem; moderate for from 15 to 25 percent sweetfem; and high for more than 25 percent sweetfem. If in doubt about any area, make ground spot-checks, especially when there are areas of high risk. Large amounts of blueberry or blackberry may increase this risk.

2. Draw boundaries of the categories on the sketch map.

3. Determine the acreage in each category.

4. To formulate a plan of action if moderate- or high-risk areas are present, read the Management Guidelines (page 44).

3. Use the risk-rating triangle to determine if risk is low, moderate, or high at each stop. Plot the percentage of sweetfem against the percentage of other hosts on the triangular graph at the right. The point at which the coordinates intercept on the graph will fall in one of the risk classes. For example, if you plot 10 percent sweetfem against 20 percent other hosts, the risk given by the graph is low. If, however, you plot 30 percent sweetfem against other hosts, the risk is high.

4. On the sketch map, place an L, M. or H at each stop to indicate low, moderate, or high risk, respectively.

5. After completing all observations, draw lines on the sketch or map that enclose areas of similar risk.

6. Estimate the acreage in each risk category.

7. To formulate a plan of action if moderate- or high-risk areas are present, read the Management Guidelines (page 44).

54

Saratoga Spittlebug Nymphal Appraisal Survey

Field or Plantation No.

County T. _

Plot No

Date.

_S._

I. TREE-UNITS

A. Number of trees in 1/10-acre (66- by 66-ft) plot

B. Average no. of branch-whorls per tree

1 2 3 4 5 Total Average

C. Average tree height (ft)

D. Calculate tree-units by multiplying A x B x C =

1 6 2 7 3 8 4 9 5 10

tree-units per plot

Total Average

11. NYMPHAL SURVEY

Take 50 systematic 1/10-milacre samples (1/10-milacre = 25 X 25 in. frame); record samples as infested (+) or not infested (-)

1 11 21 31 41 2 12 22 32 42 3 13 23 33 43 4 14 24 34 44 5 15 25 35 45 6 16 26 36 46 7 17 27 37 47 8 18 28 38 48 9 19 29 39 49 0 20 30 40 50

Count the number of infested (H-) samples

Multiply this value by 2 = percent samples infested.

Determine no. of nymphs per plot from chart

nymphs per plot Nymphs per tree unit tree-units per plot

Percent No. nymphs samples per 1/10-acre infested

10

plot

100 20 250 30 450 35 600 40 700 45 950 50 1100 55 1500 60 1800 65 2300 70 3100 75 4000 80 5900 85 9000

55

Instructions for Saratoga Spittlebug Nymphal Appraisal Survey

Saratoga spittlebug nymphs are best surveyed during the last 3 weeks in June (for greatest accuracy). You will need a sketch map of the planting with risk areas delineated (from risk-rating field form), a clipboard and pencil, four nags or stakes, a measuring pole (in feet), and a square sampling frame 25 in. by 25 in. (inside measure).

1. Survey the areas of high risk first. Survey moderate risk areas if they qualify for control.

2. Determine the number of 1/10-acre (66- by 66-ft) plots needed according to the acreage at high risk.

Acres in high risk No. of plots

1-5 1 6-10 2

11-20 3 21-40 4 40 + 5

3. Establish 1/10-acre plots, demarcating the four corners with flags or posts. Pace off the plot or use a 66-ft tape or rope.

4. Count the number of trees in the sample plot and record it on line A.

5. Determine the average number of whorls per tree and record it on line B. If the trees are the same age, you can determine this easily from five trees.

6. Measure height (to nearest half foot) of 10 trees scattered throughout the plot, calculate their average height, and record it on line C.

7. Calculate the tree-units for the plot by multiplying the number of trees (A) X average number of whorls (B) x average tree height (C). Record this value in line D.

8. Begin sampling nymphs at one corner of the plot. Drop the sampling frame and carefully examine all host plants within the frame for nymphs, which will be in spittlemasses. When you find one live nymph, stop sampling and record the nymphs as a plus (+). If no nymphs are found after examining all host plants, record the sample as negative

(-).

9. Move to next sample and repeat. Take each sample about 5 or more feet apart to get 50 samples evenly spaced throughout the plot. Regularly stagger the sampling locations so that some are taken in the lane between rows and others are taken close to the trees.

10. After taking 50 samples, count the pluses (-I-) and multiply by 2 to determine the percentage of samples infested with nymphs. The percentage of samples infested provides an estimate of the number of nymphs for the 1/10-acre plot. (See table in box on form.)

11. Calculate and record the nymphs per tree-unit by taking the number of nymphs per plot and dividing by the number of tree-units per plot. Nymphs per tree-unit gives the potential damage level.

12. Use this key to find action recommended after nymphal appraisal survey.^

Oa) Nymphs per tree-unit less than 1.0—see no. 1 Ob) Nymphs per tree-unit 1.0 or more—see no. 8

la) Trees shorter than 10 ft—see no. 2 lb) Trees 10 ft or taller—see no. 4

□ □ □

□ □ □ □ □ □ □

2a) Nymphs per tree-unit less than 0.15—evaluate again in 3 years

2b) Nymphs per tree-unit 0.15 or more—see no. 3

3a) Nymphs per tree-unit more than 0.25—evaluate next year

3b) Nymphs per tree-unit 0.15 to 0.25—evaluate in 2 years

4a) Trees from 10 to 12 ft tall—see no. 5 4b) Trees taller than 12 ft—see no. 7

5a) Nymphs per tree-unit more than 0.15—see no. 6

5b) Nymphs per tree-unit 0.15 or less—no need to reevaluate

6a) Nymphs per tree-unit more than 0,25—evaluate next year

6b) Nymphs per tree-unit 0.15 to 0.25—evaluate in 2 years

7a) Nymphs per tree-unit more than 0.40—reevaluate next year

7b) Nymphs per tree-unit 0.40 or less—no need to reevaluate

8a) Nymphs per tree-unit 1.0 to 2.0—if there is flagging or noticeable degrade, control this year; if not, reevaluate next year

8b) Nymphs per tree unit more than 2.0—control this year

iQiven near threshold values, use indicators of the previous year's feeding injury to help make a control decision. The previous year's feeding scars persist to add to the present year's injury; thus, use presence of feeding scars, flagging, and the previous insect evaluation, if available to decide if control is warranted.

56

Pesticide Precautionary Statement

Pesticides used improperly can be injurious to humans, animals, and plants. Follow the directions and heed all precautions on the labels.

Store pesticides in original containers under lock and key—out of the reach of children and animals—and away from food and feed.

Apply pesticides so that they do not endanger humans, livestock, crops, beneficial insects, fish, and wildlife. Do not apply pesticides when there is danger of drift, when honey bees or other pollinating insects are visiting plants, or in ways that may contaminate water or leave illegal residues.

Avoid prolonged inhalation of pesticide sprays or dusts; wear protective clothing and equipment if specified on the container.

If your hands become contaminated with a pesticide, do not eat or drink until you have washed them thoroughly. If you swallow a pesticide or get it in your eyes, follow the first-aid treatment given on the label, and get prompt medical attentíon. If a pesticide is spilled on your skin or clothing, remove clothing immediately and wash skin thoroughly.

Do not clean spray equipment or dump excess spray material near ponds, streams, or wells. Because it is difficult to remove all traces of herbicides from equipment, do not use the same equipment for insecticides or fungicides that you use for herbicides.

Dispose of empty pesticide containers promptly. Have them buried at a sanitary land-fill dump, or crush and bury them in a level, isolated place.

Note. This publication reports research involving pesticides. It does not contain recommendations for their use, nor does it imply that the uses discussed have been registered.

Some States have restrictions on the use of certain pesticides. Check your State and local regulations. Also, because registra- tions of pesticides are under constant review by the United States Environmental Protection Agency, consult your county agricultural agent or State extension specialist to be sure the in- tended use is still registered.

Back cover (top)—Sweeifern, the primary host of the Saratoga spittlebug. (bottom)—A spittlebug-infested plantation of red pine.

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