Kentucky Pest News, August 28, 2012
Transcript of Kentucky Pest News, August 28, 2012
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Online at:www.uky.edu/KPN
Number 1316 August 28, 2012
CORN
-Corn Earworm Moths Captures Increasing in
Vegetables
SOYBEAN
-Soybean Vein Necrotic-Associated Virus
Common in Soybean
FRUIT CROPS-Bluberry Mosaic Virus Detected in Kentucky
-Fungicide-Resistant Downy Mildew Detected
in Kentucky Vinyard
SHADE TREES AND ORNAMENTALS
-Sawflies-Late Season Pine Defoliators
LAWN AND TURF
-Leaf Rusts are Apparent
PEST OF HUMANS
-Stinging Caterpillars
-Dealing with Mosquitoes
DIAGNOSTIC LABORATORY HIGHLIGHTS
INSECT TRAP COUNTS
CORN
Corn Earworm Moths Captures Increasing inVegetablesBy Ricardo Bessin
As corn earworm pheromone trap catches increase
in late summer, sweet corn and tomato growers
may need to step up their surveillance and
management of this pest. Corn earworm is knownby several common names including tomato
fruitworm, soybean podworm, and cotton
bollworm. Generally it is a fruit feeder and can
attack a wide variety of crops including tomatillo,
pepper, okra, and green beans.
Figure 1. Corn earworms are less sensitive to pyrethroid
insecticides than a decade ago.
At this time of the year we usually experience
much larger populations of this pest. The female
moth is attracted to fields that are flowering or
fruits. Field corn that is beginning to dry drown is
one source of the adult moths as they complete
their development in corn ears, the other source is
through migration from southern areas. Storm
fronts from approaching from southern states can
bring large numbers of corn earworm moths andother pests.
Sweet corn producers and growers of fruit
vegetables may need to step up their game to
prevent damage from this insect. Over the pastseveral years, entomologists in the Midwest have
noted reduced susceptibility to the pyrethroid
insecticides (IRAC group 3) by corn earworm, but
are hesitant to call it resistance. Because of this,growers should be ready to evaluate the level of
control after an insecticide spray. Sweet corn
growers need to carefully manage corn earwormwhile the ears are silking to prevent the larvae
entering ears. Generally commercial growers willneed to spray an insecticide targeting corn
earworm on three to five day intervals until the
silks dry. Sprays need to be directed to the center
third of the plant. With tomatoes and other fruit
vegetables, growers should monitor plants anddeveloping fruit for signs of fruitworm activity
Lexington, KY 40546
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and spray as needed. Fruitworms do not enter the
fruit but will chew up to -inch cavities in the
fruit.
Figure 2. Yellow-striped armyworm numbers also
increasing.
Yellow-striped armyworm numbers are also
increasing and they will cause similar damage to
tomato fruit. The young larvae are foliage feeders
while the larger larvae attack the fruit. In terms of
management, they can be treated as tomato
fruitworm when scouting or for selecting controls.
SOYBEAN
Soybean Vein Necrotic-Associated Virus
Common in SoybeanBy Don Hershman
A new virus disease of soybean, soybean vein
necrotic-associated virus (SVNaV), is fairly
widespread throughout Kentucky at this time. We
have seen symptoms of SVNaV at low levels inKentucky for the last 15 years, but the disease has
only recently been named and characterized (I.
Tzanetakis and co-workers, 2009; J. Zhou and co-
workers, 2011). The original description of
SVNaV was from field-grown soybeans collected
in Tennessee in 2008. SVNaV is thought to be
transmitted to soybean by soybean thrips, which
were quite common this season due to the drought.
Thus far, SVNaV has been confirmed in 12 states:
AR, DE, KY, KS, IL, MD, MO, MS, NY, PA, TN,
and VA.
Although SVNaV is easy to find in many fields, I
would be surprised if the disease is severe enough
in any field to result in measurable yield losses. Infact, I am not aware of any instances in the U.S.
where measurable yield losses have been
attributed to SVNaV. It is, however, an emerging
disease that merits additional study and
monitoring.
Look for leaves with faint to distinct oak leaf
patterns that range from a whitish to bright yellow
(Fig. 1). Over the course of 2-3 weeks, the oak
leaf symptom will turn yellow to brown (Fig. 2).
Older lesions (Fig. 3) are commonly infected by
saprophytic/secondary fungi, especiallyCercospora spp. Symptoms tend to be most
evident in the upper 1/3 of the canopy. I have
been seeing symptoms of this disease for well overa month, but their frequency and intensity are now
peak. My preliminary observations suggest that
some soybean cultivars may be more susceptible
to SVNaV than others. To date, no resistance to
SVNaV has been identified. No control measurestargeting thrips or SVNaV are warranted.
Figure 3. Typical initial oak leaf pattern symptom caused by
soybean vein necrotic-associated virus (photo by D.
Hershman).
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(Soybean photos continued from previous page)
Figure 4. Range of symptoms caused by soybean vein
necrotic-associated virus (photo by D. Hershman).
Figure 5. Old lesions of soybean vein necrotic-associated
virus colonized by a host of secondary fungi, especially
Cercospora spp. (photo by D. Hershman).
FRUIT CROPS
Blueberry Mosaic Virus Detected in KentuckyBy Nicole Ward, UK Extension Plant Pathologist
Blueberry mosaic virus was confirmed in ablueberry orchard in central Kentucky this
summer. This is the first report of blueberry
mosaic in the state. The virus has not previously
been found in southern states, but it has been
reported in Michigan, Indiana, New Jersey, NewYork, Oregon, Washington, and British Columbia.
Formerly considered a disorder, blueberry
mosaic has only recently been classified as a virus.
Not much else is known about it. Highbush
cultivars Bluecrop, Pioneer, Concord,
Earlibule, and Jersey are among the susceptible
cultivars. Virus symptoms have not been reportedin rabbiteye blueberry. Limited research has beenconducted thus far, but it is under evaluation by a
team of researchers at the USDA-ARS Marucci
Center in New Jersey.
SymptomsFoliar symptoms include mottling and mosaic-
patterned characteristics on leaves. Patterns rangefrom mild to brilliant with yellow, orange, and/or
red colorations (see figures 6 through 9). Mosaic
symptoms are not always produced each year, and
environmental conditions may affect symptomdevelopment. It is possible that during cool
seasons, symptoms are more pronounced. Thus,
under ideal conditions, symptoms may appear
suddenly, and it may appear that spread is rapid.
Infected plants often result in reduced fruit load.
Yield losses of 15% have been reported on
Bluecrop in Michigan. Fruit on infected plants
have been shown to ripen later than noninfected
fruit, and fruit quality is low.
SpreadThe vector (carrier) of the virus is not known.
Researchers report that blueberry mosaic is not
transmissible by mechanical means (i.e. pruners).
However, the virus is graft transmitted. Becausevirus particles are systemic (dispersed throughout
the vascular system), once infected, all plant parts
are infected, even when symptoms are absent.
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Thus, cuttings should never be taken from a virus-
infected plant.
As mentioned above, the vector of blueberry
mosaic virus is not known. Therefore, growers areencouraged to destroy infected plants until it is
clear on how the virus spreads. Whether an insectvector is involved is yet to be determined.
Current research indicates that the virus is slow-spreading (if at all) under field conditions.
However, in Michigan, spread is rapid. So far, the
reason is unknown.
TreatmentThere is no cure for plant viruses, including
blueberry mosaic. Growers should remove
infected plants and destroy them by burning or
burying. Remove all roots within soil, as well.Scout orchards, especially nearby plants, several
times during the growing season. Contact a local
extension agent if a plant appears suspicious.
Most importantly, purchase plants from a
reputable grower. Visit nurseries before plantpurchase and ask to inspect parent plants.
Furthermore, a virus-free certification is always
worth the extra cost.
Figure 6. Foliar symptoms include mottling and mosaic-
patterned characteristics on leaves.
Figure 7.
Figure 8. . Patterns range from mild to brilliant with yellow,
orange, and/or red colorations.
Figure 9.
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Fungicide-Resistant Downy Mildew
Detected in Kentucky VineyardBy Nicole Ward, UK Extension Plant Pathologist
This summer, a grape grower in central Kentucky
reported persistent downy mildew in his vineyard.He noted that regular applications of Abound andPristine fungicides failed to manage the disease.
After laboratory analysis, the pathogen was
deemed completely resistant to the two fungicides
at the lowest recommended rates and 85%
resistant at the highest recommended rates.
What is fungicide resistance?In the simplest terms, pathogens become resistant
to fungicides when the chemical no longer
manages disease symptoms. However, even the
most effective fungicides fail to completelyeradicate a pathogen population. There are always
a few fungal spores or other fungal inoculum that
survive the pesticide application. Those survivors
may be the result of ineffective spray coverage,but individual pathogens may have a trait that
provides some type of resistance to the fungicide.
Think back to high school biology when we
learned the theory of survival of the fittest.
Unfortunately, a single survivor can multiply into
thousands of individuals while passing that
resistance gene onto its offspring, much the way
our parents passed on eye color to us.
How did resistance develop?Consider that it is highly unlikely that a fungalpopulation will incur resistance to more than one
chemical type, at least over the short term. As a
fungal population can become resistant to a single
chemical, growers should rotate sprays with a
different chemical group. These chemicalrotations can become confusing, and many
growers do not fully understand the concept of
chemical groups.
Chemical groups are classified by biochemical
mode of action, not necessarily by active
ingredient. For example, within the strobilurin
group of fungicides, active ingredients include
azoxystrobin, pyraclostrobin, trifloxystrobin, and
kresoxim-methyl, all of which are quinone-outside
inhibitors. Because information on biochemical
modes of action can be confusing for growers, the
Fungicide Resistance Action Committee (FRAC)
developed numeric codes that represent these
chemical groups. Strobilurins are classified as
FRAC group 11. These codes appear on the top
right side of all pesticide labels. Thus, growers
may simply refer to the coded chemical group
number on labels as opposed to depending uponcomplex information such as mode of action.
Considering that all fungicides within the same
group have the same mode of action, it is clear that
if a grower fails to properly rotate fungicide
groups, fungicide resistance risk is high.Additionally, fungicide labels indicate the
maximum number of applications allowed per
growing season. A maximum of four applications
of strobilurins are allowed per growing season.The grower mentioned above used Abound and
Pristine fungicides consistently over a two-yearperiod, exceeding the maximum number of
applications and failing to rotate with a different
chemical group. This rapidly induced thedevelopment of a resistant population of the
downy mildew pathogen.
Figure 10. Abound fungicide is classified as a FRAC Group
11 fungicide. The chemical group code appears on the top
right corner of fungicide labels.
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How does a grower know if a resistant population
developed?Pathogen populations do not begin as 100%
resistant. In fact, resistance develops gradually.
Thus, growers should be aware of efficacy anddisease control. If a product(s) begins to become
less effective over time, he should contact his localExtension agent immediately.
What next?If resistant pathogen populations develop within avineyard, growers should immediately stop using
the fungicide in question and all others in the same
FRAC group. With the assistance with an
Extension agent or specialist, growers should
identify other fungicides that will effectively
manage disease. In the aforementioned case, the
grower stopped using strobilurin fungicides and
substituted a phosphorous acid fungicide (ProPhyt,Rampart, etc.) for management of downy mildew.If strobilurins are used for management of other
diseases, tank-mix with another product (within a
different FRAC group) that provides downy
mildew control.
More InformationFungicide resistance can appear complicated, so
growers should not hesitate to seek assistance in
development of a spray program. Contact
University of Kentucky Cooperative Extension
agents or specialists for assistance.
SHADE TREES AND ORNAMENTALS
Sawflies Late Season Pine DefoliatorsBy Lee Townsend
Sawflies are members of the insect order
(Hymenoptera) that includes ants, bees, and
wasps. The larval stage has a caterpillar-like body
that may be brightly marked with stripes or spots.Some species change significantly in appearance
as they grow, making identification confusing.
Large numbers of sawflies can strip the needles
from a tree in a short period. Several species can
be found on pines in Kentucky.
The European pine sawfly is one that is active at
this time of year. These olive green larvae with
black stripes and shiny black heads can feed on
many pines including Scotch, Eastern white, andAustrian. They feed on the previous year's needles
and do not damage new needles. These sawflies
can feed on twig bark, causing growth deformities.
Trees are seldom killed by the feeding of this
insect during a single season. Full grown larvae
are about 1 inch long.
Figure 11. Introduced pine sawfly larva
The introduced pine sawfly has a black head and
black body that is covered with yellow and white
spots. They prefer the needles of eastern white
pine but also will eat Scotch, red, Austrian, jack,
and Swiss mountain pine. Short leaf and Virginia
pines have been attacked but usually are not
heavily damaged.
Feeding is most severe in the crown to upper half
of the tree but heavily infested trees can be
completely defoliated. If this occurs after the
winter buds have formed, many branches or even
the entire tree can be killed. There are two
generations each year. The second generation ofthis sawfly feeds on both old and new needles
during August and September.
Sawfly populations are usually controlled by
combinations of natural enemies, predators,starvation, disease, or unfavorable weather.
Outbreaks can occur when natural control does not
produce high mortality. Regular inspection of
pines will help to detect sawfly infestations beforethe larvae reach a size that can cause significant
defoliation. Since eggs are laid in clusters, feeding
by groups of larvae can cause unsightly damage to
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ornamental or landscape plantings, as well as
nursery trees
If only a small number of colonies are present and
accessible, they can be handpicked, shaken off, orpruned from the tree and destroyed. Some of the
insecticides that can be used for sawfly control arelisted by the common name of the active
ingredient followed by an example brand name.
Acephate - Orthene Turf, Tree & OrnamentalSpray, bifenthrin- Ortho MAX Lawn & Garden
Insect Killer, carbaryl - Sevin, cyfluthrin - Bayer
Multi-Insect Killer Concentrate, and permethrin -
Ortho Tree, Shrub, and Lawn Spray. Although
sawflies look like caterpillars, they are not
susceptible to Bt sprays.
Stinging CaterpillarsBy Lee Townsend
Late season caterpillars are active now. Many use
camouflage or secretive behavior to avoid
predators, especially birds. A few are protected
and advertise their presence by bright warning
markings. These should be avoided. The
distinctive larva of the white flannel moth is oneof the less common species. They feed on a variety
of deciduous trees and shrubs. These caterpillars
do not actively sting like a bee or wasp. Contact
usually comes as a person accidentally brushes
against a caterpillar that they did not see.
Figure 12. White flannel moth caterpillar. Beware of insects
with bright warning markings.
Stinging caterpillars have some brittle, hollow
spines that are connected to venom glands in the
body. These spines easily penetrate skin and break
off. Then, the irritating venom goes to work.
Reactions to the chemicals vary from slight
irritation to pustules, inflammation, and sometimes
intense pain.
Wide masking tape can be applied to the site to liftthese tiny spines from the skin. To avoid further
injury, the area should not be rubbed until they are
removed. The wound area should then be washedwith soap and water. Place an ice pack or cold
compress on the wound intermittently (15 minutes
on and 15 minutes off). See a physician if there is
a severe or persistent reaction to the toxin.
Figure 13. Close up of stinging spines on spots down the
back of the white flannel moth caterpillar.
More information on stinging caterpillars found in
Kentucky is available in
www.ca.uky.edu/entomology/entfacts/ef003.asp.
LAWN AND TURF
Leaf Rusts Are ApparentBy Paul Vincelli
Leaf rust diseases are apparent on several cool-
season grasses. Leaf rusts are readily recognizable
in the field by the tiny, orange-colored pustulesthat contain powdery spores which erupt from
within the leaf blade (Fig. 1). These pustules
eventually cause leaf blades to turn yellow and dry
up. The disease does not kill turf outright but can
weaken it, if severe.
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Under Kentucky conditions, leaf rusts of
turfgrasses are usually most severe in turfgrass
stands that are growing slowly, such as those that
are low in nitrogen or soil moisture. Since autumn
is a very important time to fertilize swards of cool-season turfgrasses in Kentucky in order to help
promote root growth and overall vigor, swards thatare showing substantial levels of rust may simply
need to be fertilized or irrigated. Alleviation of
compaction through aerifying can also help.
For particularly high- value swards where there
may be interest in spraying fungicides, the most
effective products are listed in the UK Extension
publication, Chemical Control of Turfgrass
Diseases, available at
http://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pd
f. Be aware that several fungicides labeled for rust
control on turfgrass arenot labeled for home lawnuse (but are labeled for other turf uses). Thus, if
treating a home lawn, be sure the product is
labeled for that particular use.
Figure 14. Highly magnified view of a pustule of leaf rust,
showing orange-colored spores.
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PESTS OF HUMANS
Dealing With MosquitoesBy Mike Potter and Lee Townsend
Human cases of West Nile Virus have beendetected recently in Kentucky. Reducing exposure
to mosquitoes and eliminating breeding sites, if
possible, are key steps in reducing exposure.
Here are some tips to reduce chances of exposureto mosquitoes:
1. Eliminating breeding sites on your property can
be effective because mosquitoes tend to stay near
them after emerging as adults.
Dispose of old tires, buckets, aluminum cans, and
plastic sheeting or other items that can hold water.
2. Check for stagnant water in drinking troughs
flush out if necessary3. If practical treat water that cant be eliminatedby using products like mosquito donuts or or
granules labeled for that use. Various products
containing the mosquito- specific active
ingredients can be used.
Adult mosquitoes prefer to rest in moist, shady
areas such as dense vegetation during the daytime.
Consequently, homeowners should remove tall
weeds and overgrown vegetation from their yards.
To further reduce intolerable levels of biting adult
mosquitoes, residual insecticides can be applied toshrubs, hedges and other shaded areas, such as
under decks and along foundations.
Recent research by University of Kentucky
entomologists indicates that such treatments
effectively suppress nuisance, biting mosquitoes
for about a month. Residual mosquito sprays are
often best applied by professional pest control
firms. Homeowners opting to try this themselves
should use lawn and garden insecticides
containing permethrin (e.g., Ortho Mosquito B
Gone, Spectracide Mosquito Stop), cyfluthrin(Bayer Advanced Powerforce Mosquito Killer),
bifenthrin (e.g., Ortho Home Defense Max), or
lambda cyhalothrin (Spectracide Triazicide). For
homeowners, a hose-end sprayer is usually most
effective for making such applications.
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Exclusion - Mosquitoes can be kept out of homes
by securely screening windows, doors and
porches. The occasional mosquito found indoors
can be eliminated with a fly swatter. Aerosol-type
insecticides labeled for mosquitoes, gnats, andother flying insects seldom provide much relief at
the dosages applied by householders.
Topically-Applied Repellents - Repellents will
help prevent bites when spending time outdoors.Traditionally, the most effective mosquito
repellents contained the active ingredient diethyl
toluamide (DEET) ranging from 5% to 40%.
Higher percentages of DEET in the ingredients
provide longer protection. Low -percentage
formulations (10% or less) are suitable for shorter
periods outdoors (e.g., 1 to 2 hrs), and are
recommended for use with young children. Earlier
this year, two new mosquito repellents wereregistered by the U.S. Environmental Protection
Agency and recommended as alternatives to
DEET by the Centers for Disease Control and
Prevention. Picaridin (7% Cutter Advanced) and
Lemon eucalyptus oil (30% Repel Lemon
Eucalyptus) provide relief for about 2 to 4 hrs.
Unlike DEET-based repellents, Picaridin is
essentially odorless and Lemon eucalyptus oil has
a lemon scent. For many people, the new products
will also have a more pleasing feel on the skin.
Both repellents should be appearing on store
shelves soon. Always read and follow directionson the container.
Other Control Possibilities - Many consumer
products claim to attract, repel, capture or kill
mosquitoes. Most of these devices do not
appreciably reduce mosquito abundance or
incidence of bites, or else their claims areunproven. Electrocuting devices or "bug zappers"
using ultraviolet light as an attractant are generally
ineffective in reducing outdoor populations of
mosquitoes and their biting activity. Studies
indicate that mosquitoes make up only a tinypercentage of the insects captured in such traps.
The majority are moths, beetles and other harmless
night flying insects. Other types of mosquito traps
utilize carbon dioxide, warmth, light, and variouschemicals (e.g. octenol) as attractants and claim to
capture tremendous numbers of adult mosquitoes.
Such devices can be quite expensive. Performance
claims to the contrary, such traps seldom have
been shown to reduce populations of biting
mosquitoes on one's property, or the frequency of
bites. In some situations, they could even attract
more mosquitoes into the area they were meant to
protect.
Advertisements for portable electronic devicesusing high frequency, ultrasonic sound routinely
appear in magazines, claiming to keep mosquitoes
and other pests at bay. Some supposedly repel
mosquitoes by mimicking the wing beat frequency
of a hungry dragonfly. Scientific studies have
repeatedly shown these devices to be of negligible
benefit in deterring mosquitoes and reducing bites.
Save your money, as these devices seldom if ever
provide any appreciable measure of protection.
Citronella oil does have mosquito-repelling
properties and the scented candles can providesome protection. For maximum effect, use
multiple candles placed close (within a few feet)
of where people are sitting. A single candle
located at the center or edge of a picnic blanket
probably will not provide much benefit other than
atmosphere. Mosquito-repellent plants, garlic, and
other oft-advertised botanical products generally
are ineffective.
DIAGNOSTIC LAB HIGHLIGHTS
By Julie Beale and Paul Bachi
During the past week we have diagnosed thrips
injury and Rhizoctonia root rot on corn; summer
black stem on alfalfa; frenching on tobacco; brownrot on peach; and Phytophthora fruit rot on
pumpkin.
On ornamentals and turf, we have seen Pythium
root rot and Rhizoctonia root/stem rot on
calibrachoa; downy mildew on impatiens;bacterial soft rot on iris; anthracnose on liriope;
Botryosphaeria canker on rhododendron; rosette
on rose; anthracnose on bentgrass; summer patch
on bluegrass; and brown patch on fescue.
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2012 INSECT TRAP COUNTS
August 16 - 23
Graphs of insect trap counts for the 2012 season
are available on the IPM web site at -
http://www.uky.edu/Ag/IPM/ipm.htm.
View trap counts for Fulton County, Kentucky at -http://ces.ca.uky.edu/fulton/InsectTraps
Note: Trade names are used to simplify the information
presented in this newsletter. No endorsement by the
Cooperative Extension Service is intended, nor is
criticism implied of similar products that are not
named.
Location Princeton, KY Lexington, KY
Black cutworm 10 0
Armyworm 20 1
Corn earworm 390 3
European corn
borer
0 0
Southwestern
corn borer
422 0
Fall armyworm 91 0