This dissertation has beenmicrofilmed exactly as received 66-13,704

HARAMOTO" Frank Hiroshi, 1924-BIOLOGY AND CONTROL OF BREVIPALPUS'PHGENICrs (GEIJSKES) (ACARINA:TENUIPALPIDAE).

University of Hawaii, Ph.D., 1966Zoology

University Microfilms, Inc., Ann Arbor, Michigan

.BIOLOGY AND CONTROL

OF

BREVIPALPUS PHOENICIS (GEIJSKES)

(ACARINA: TENUIPALPIDAE)

A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF THE

UNIVERSITl OF HAWAII IN PARTIAL FULFILLMENT

OF THE REQUIREMENTS FOR THE DEGREE OF

DOC TOR OF PHILOSOPHY

IN ENTOMOLOGY

JANUARY 1966

By

Frank Hiroshi Hararnoto

Thesis Comrn.ittee:

D. Elmo Hardy, Chairm.anHenry A. BessMarnoru IshiiWallace C. MitchellToshiyuki Nishida

iii

TABLE OF CONTENTS

· . . . . . . . . . .· . . . . . . . . . . . .

· . . . . . . . . . . . .

· . . . . . . . . . . . .

v

iv

1

3

5

10

14

24

42

57

67

7I

78

91

97

101

. . . . . . .

. .. . . . . . . .

. .

. . . . . .

• • 0 • • • • • • • • •

• • • • • • • • • • • •

• • • • • • • • • • • • •

• • • a • • • • • • • • •

· . . . . . . . . . . . .

· . . . . . . . . . .· . . .

. . .CHEMICAL CONTROL.

DISCUSSION •••

SUMMARY • • 0 • • ••

REFERENCES CITED • • ••

POPULATION STUDIE;

NA TURAL CONTROL FACTORS

LIFE HISTOR Y • • • • • • • • •

BIOLOGICAL OBSERVATIONS

METHODS AND MATERIAJ..S •

DE;CRIPTION OF liFE STAGE;

LIST OF TABLE; ••• 0 •

liST OF ILLUSTRATIONS

INTRODUCTION ••••••••

TAXONOMIC STATUS • • • • •

DISTRIBUTION • • • • • • • •

HOST PLANTS ••••••

Table

I.

il.

ID.

IV.

V.

VI.

Vil.

VID.

List of Tables

Geographical distribution of BtevipalpusphoPcnicis (Geij skes) •• • • • • • • • • • • • • •

Monthly maxiInum-minimum temperature s forHonolulu and Kaneohe, Oahu, and for Kahului,Maui, during 1962 and 1963 ••••••••••••••

List of host plants of Brevipalpus phoenicis(Geij skes) in Hawaii ••••••••••••••• ••

Average measurements of ~he life stage s ofBrevipalpus phoenicis (Geijskes). • I> •••••••

Effect of temperature and humidity on the lifestages of Brevipalpus phoenicis (Geijskes) •• 0 ••

Performance of different pesticides against theadults of Brevipalpus phoenicis (Geij skes) •••••

Number of eggs of Br,evipalI?us phoenicis(Geij skes) counted on treated surface one weekafter application of the different pesticides • • • • •

Ovicidal effect of different pesticides on theeggs of Brevipalpus phoenicis (Geijskes) ••••••

iv

6

9

11

27

44

86

88

90

Figure

1.

List of Illustrations

Distribution map of Brevipalpus phoenicis • • • • •

v

7

2. Rearing unit used in the constant temperatureand humidity experiments • • • • .. • • • • •

Rearing unit used in the chemical control studiesof BrevipalP\;1s phoenicis ••••••••••

• •

• •

18

21

5.

6.

7.

8.

9.

10.

Outline drawing of Brevipalpus phoenicis femaleehowing location and nomenclature of thesetae and plate s ••••••••••.••••• 0

Egg of Brevipalpus phoenicis. • • • • • • • • • •

Larva of Brevipalpus phoenicis. • • • • • • • • •

Protonymph of Brevipalpus phoenicis • • • • • • •

Deutonymph of Brevipalpus phoenicis • • • • • • •

Female of Brevipalpus phoenicis • • 0 • • • • • •

Variation in color patterns of females ofBrevipalpus phoenicis • • • • • • oi • • • 0 • • •

25

29

31

33

35

37

38

11. Male of Brevipalpus phoenicis . . . .0. . . . . 41

12. Mean number of eggs laid per week by 25Brevipalpus phElenicis female s • • • • • 0 0 0 • • 53

13.

14.

Longevity of the adults of Brevipalpus phoenicisat the different temperatures in combinationwith 65 to 70 per cent relative humidity • • • •

Feeding injury caused by Brevipalpus rhoenicison papaya fruit • • • • • 0 0 • • • • • • • •

• •

• •

56

59

IS.

16.

17.

Feeding injury caused by Brevipalpus phoenicison papaya fruit • • • • • • • • • • • • • • •

Feeding damage caused by Brevipalpus phoenicison passion fruit. • • • • • 0 • • • • • • • •

Egg and adult densities and fluctuations ofBrevipalpus phoenicis populations. • 0 0 0

o 0

vi

61

62

68

18.

19.

Injury caused by Chlorobenzilate •

Injury caused by Pentac • 0 •

o 0 0 . . . . .• •

82

83

20. Injury caused by ovex .0 . . . . • • • I! 84

rnTRODUC TION

The red and black flat mite, Brevipalpus phoenicis (Geijskes),

has been reported from many countries since its discovery in Holland

in 1939 (Geij skes, 1939). This mite is not endemic to the type locality,

but is believed to have a tropical origin. However, because of its

extensive geographical distribution and host range, the native home of

this mite cannot be established.

Baker in 1949 reported that several species of Brevipalpus have

been found to be pests of cultivated plants, and although not as impor­

tant as the spider mites they are serious enough at times to warrant

investigations of their biology and control. Since then, Manglitz and

Cory (l953) and Morishita (1954) have studied in detail the biology and

control of B. californicus (Banks) and of Jh obovatus Donnadieu,

respectively. These two species along with!h phoenicis and!h lilium.

Baker make up the known fauna of false spider mites of the genus

Brevipalpus in Hawaii. Of these, !h phoenicis is of most concern here

in Hawaii for besides damaging many ornamental plants, it attacks

two crops of significant economic importance: papaya and passion fruit.

~ phoenicis may have been in Hawaii previous to its description

date for in 1936 Marlowe (1937) reported a mite injury on papaya fruits

with symptoms similar to those now known to be caused by this species.

Despite its early presence in Hawaii, very little work has been done in

the past on this important mite by other worker So Therefore, a detailed

biological study ofl!: phoenicis has been made and the findings are

presented in this thesis so that they may serve as a basis for further

studies of this as well as other species of phytophagous mites.

2.

3.

TAXONOMIC STATUS

B. phoenicisbelongs to the order Prostigmata, sl!perfa:mily

Tetranychoidea, and fa:mily Tenuipalpidae. Geij skes in his descrip­

tion of phoenicis in 1939 placed it in the genus Tenuipalpus. At that

time, Brevipalpus was considered as a synonym of Tenuipalpus; how­

ever, Baker in 1945 established the validity of the for:mer and

reinstated it as a generic name.

Unaware of the extent of possible variations in certain charac­

ters of B. phoenicis, Baker P949) na:med~ yothersi, ~ mcbridei,

and B. papayensis as separate entities based on the differences noted

in the size of the dorso-lateral setae of the nymphs of yothersi and

:mcbridei, and on the presence of a prominent edentation on the second

palpal segm.ent, as well as on the less distinctive areolate pattern on

the dorsum of papayensis adults. In later studies, these characters

were found to be :merely intraspecific variations, and thus, the three

names were declared as synonyms of B. phoenicis (Pritchard and

Baker, 1951).

In Hawaii, prior to 1951, B. phoenicis was referred to as~ bio­

culatus McGregor (Holdaway, 1941), and as B. papayensis (Baker,

1949). The former is a misidentification and a synonym of B. obovatus,

a species very similar in gross morphology to B. phoenici~, and the

latter is a synonym. of B. phoenicis. The na:me, B. papayensis, was

proposed in 1949 by Baker for the :mites on papaya collected in 1941 by

4.

w. C. Look from Kailua, Oahu, Hawaii.

At present, there is no appt"oved common name for B.

phoenicis. The common name, the red and black flat mite, was first

used by Muma (1961) and is adopted to referring to~ phoenicis in

- this paper.

DISTRIBUTION

!h E!!.oenicis is widely distributed in both continental and insular

areas, primarily throughout the tropics of the world. Of the 28

distributional records, 18 have been reported from somewhere within

the boundarie s of the Tropic of Cancer to the north and the Tropic of

Capricorn to the s·outh (Fig. 1 and Table I). The northernmost area

from where B~ phoenicia has been reported is Holland (Geijskes, 1939)

and the southernmost is Argentina (Baker, 1949). The few reports of

recoveries of this mite from other than the tropics probably represent

temporary establishments as a result of dispersal from the generally

favorable range into pockets of favorable environment. The outbreaks

of ~ phoenicis reported in glasshouses in Europe are exam.ples of such

dispersal and fortuitous establisbm.ents. Since its initial description in

Holland in 1939, B. phoenicis was not observed again in Europe until

1951 when it was found infesting Phoenix canariensis Hort. in glass­

houses in Vienna, Austria (Dosse, 1957). The only areas outside the

tropics where B. phoenicis is firmly established are in Florida (Muma,

1958) and in the Mediterranean region (Baker, 1949; Attiah, 1956; and

Di Martino~ 1960) where the climate is mild and similar to that of the

tropics.

In Hawaii, B. phoenicis has been recovered from the islands of

Maui, Hawaii, Oahu, and Kauai. It is generally well distributed along

the coastal plains and foothills up to about 1, 000 feet in elevation.

6.

TABLE I. GEOGRAPHICAL DISTRIBUTION OF BREVIPALPUSPHOENICIS (GEIJSKES)

Continent

Africa

Asia

Europe

North America

Area *Belgian Congo (1)Egypt (Z)Kenya (3)Mauritius (4)Tanganyika (5 )

Aden Protectorate (6)Australia (7)

Ceylon (8)Formosa (9)India (10)Malaya (11)Philippines (IZ)

Austria (13)Holland (14)Sicily (15)Spain (16)

California (17)Cuba (18)Florida (19)Mexico (ZO)Puerto Rico (Z1)Washington, D. C. (ZZ)

Reference

Baker and Pritchard, 1960Attiah, 1956Pritchard and Baker, 1958Mou1ia, 1958Pritchard and Baker, 1958

Knorr, et al., 1961Commonwealth Institute of

Entomologyp 1959Baptist and Ranaweere, 1955Pritchard and Baker, 1958Pritchard and Baker, 1958Pritchard and Baker, 195ZRimando, 196z

Dosse, 1957Geijskes, 1939Di Martino, 1960Baker, 1949

Pritchard and Baker, 195ZBaker, 1949Baker, 1949DeLeon, 1961Cromroy, 1958Baker, 1949

Pacific Islands Hawaii (Z3)

South America Argentina (Z4)Brazil (Z5)Paraguay (Z6)Trinidad (Z7)Venezuela (Z8)

Baker, 1949

Baker, 1949Rossetti, et al., 1959Nickel, 1958Pritchard and Baker, 195ZKnorr, ~t al., 1960

* Numbers after localities correspond to those on map in Figure 1.

---~--------

Figure 1. Distribution map of Brevipalpus Eoenicis (Geijskes)-J.

8.

Also, papaya and passion fruit, two favorable hosts of ~ phoenicis,

are well adapted and grown extensively in many of these areas.. In

1964 there were approxim.ately 1,350 acres in papaya and 250 acres

in passion fruit in Hawaii. The climatic conditions in the areas where

these crops are grown are warm, hUID.id, and conducive for year round

reproduction of this false spider mite. The monthly maxim.UID. and

minim.UID. temperatures for the period of this study, January, 1962 to

December, 1963, for Kaneohe, Oahu, where papaya is very often

heavily infested by B. :phoenicis, for Kahului, Maui, where serious

damage by this mite to pas sion fruit has occurred, and for Honolulu,

Oahu, where this mite is very common on many ornamental plants,

are presented in Table II. The temperature in these areas seldom

approaches the maxima and mini.m.a shown in Table II but usually

fluctuates within a few degrees from the mean. In one such area, Wai­

manalo, Oahu, where ~ phoenicis outbreak was first seen on papaya,

the mean temperature, the daily temperature range, and the annual

temperature range have been recorded as 23.9°e, 7. 2oe, and 4.4oe,

respectively (Ripperton and Hosaka, 1942). The hUID.idity condition

in these areas is relatively high and seldom drops below 50 per cent.

B. phoenicis has not been recovered from areas above 2, 500 feet

in elevation despite careful search on many kinds of plants. Tempera­

ture is more variable in the upper areas than below (Ripperton and

Hosaka, 1942)0 In the upper areas, B. obovatus and B. californicus

were frequently encountered.

TABLE II. MONTHLY MAXIMUM-1vfiNIMUM TEMPERATURES FOR HONOLULU ANDKANEOHE, OAHU, AND FOR KAHULUI, MAUl, DURING 1962 AND 1963.

Temperature °cMonths 1962 1963 1962 1963 1962 1963

Max. Min. Max. Min. Max. Min. Max. Min. Max. Min. Max. Min.

Honolulu Kaneohe Kahului

January 27.2 19.4 27.2 16.1 28.3 19.4 27.2 17.8 28.9 13.9 27.8 12.2February 27.8 14.4 27.8 17.2 28.9 16.1 28.3 18.9 28.9 II. 7 29.4 14.4March 26.7 18.9 28.3 17.2 27.8 17.8 28.3 18.3 30.6 15.0 30.6 15.6April 28.3 19.4 27.2 18.3 28.9 20.0 28.3 20.0 31. 7 16.1 30.0 17.8May 27.8 20.5 28.3 17.8 28.9 20.0 27.8 18.9 31. I 16.7 31. 1 16.7June 28.9 21. 7 28.9 20.5 28.9 21. 7 28.3 21. 7 31. 7 16.7 31. 7 16.7July 29.4 21. 1 28.9 21.7 28.3 21.1 28.9 21. 7 31. 7 18.3 31. 7 18.9August 29.4 21. 7 30.0 22.2 29.4 22.2 30.0 23.3 31.7 '17.8 32.8 18.9September 28.9 21. 1 29.4 20.5 29.4 22.2 30.0 22.8 32.8 16.7 31. 7 18.3October 29.4 20.0 29.4 20.0 30.0 2.1.1 29.4 21.7 31.7 15.0 32.8 17.8November 27.8 21.1 28.9 20.5 28.3 21.7 28.9 20.5 31.1 16.7 31.1 16. IDecember 26.7 15.6 28.3 18.3 27.8 18.3 28.9 20.0 29.4 12.2 29.4 13.9

AVERAGE 28.2 19.6 28.6 19.2 28.7 20.1 28.7 20.5 30.9 15.6 30.8 16.4

I. Readings furnished by the U. S. Weather Bureau.

i

-.D.

10.

HOST PLANTS

Phoenix sp., a greenhouse palm, was reported as the first host

plant of.!h phoenicis in 1939. Since then, many different kinds of

plants have been reported by several authors as infested by this

species of mite in different parts of the world (Cromroy, 1958;

Pritchard and Baker, 1958; Baker and Pritchard, 1960; DeLeon, 1961;

and Rimando, 1962). To date about 80 genera of plants have been

listed as hosts of~ phoenicis.

Previously, only seven species of plants have been recorded as

hosts of B. phoenicis in Hawaii (Pritchard and Baker, 1952; and

Chilson, 1959), but some 39 species of plants belonging to 27 families

were found infested during this present study. Papaya (Carica papaya

L.), passion fruit (Passiflora edulis f. £lavicarpa Degener), hemi­

graphis (Hemigraphis colorata (Bl.) Hallif.), :anthurium. (Anthurium.

andraeanum. Lind.), and leInon (Citrus liJ:nonia Osbeck), are excep­

tionally favorable hosts of~ phoenicis. Only those plants which

contained all stages of the Inite in sufficient num.ber s were included in

the host list shown in Table ill. Although the list is by no means

cOlnplete, it does show that B. phoenicis is polyphagous. Many Inore

plants, belonging to the families listed in Table ill, are likely hosts

of this Inite; however, it must be cautioned here that two other species

of false spider Inites. B. obovatus and B. californicus, which look

very much like ~ :e!:.0enicis coexist on m.any plants. There also

TABLE m. LIST OF HOST PLANTS OF BREVIPALPUSPHOENICIS (GEIJSKES) IN HAWAII

Family Species

Acanthaceae Hemigraphis coloIata (Bl. )Ballif.

Aizoaceae Sesuvium }.i.,jrtulacastrum L.

Anacardiaceae Mangifera indica L.

Apocynaceae Allamanda cathartica L.

Araceae Anthurium andraeanumlind.

Araliaceae Nothopanax guilfoylei(Gogn. and March.) Merr.

Bignoniaeceae Bignonia venusta Ker.

Cannaceae Canna indica L.

Garicaceae Carica papaya L.

Compositae Eupatorium glandulosumHBK.

Bidens pilosa L.

Convolvulaceae Ipomoea batatas (L.) Poir.Ipomoea pes-caprae (L. )

Sweet

Cucurbitaceae Momordica balsamina L.

Euphorbiaceae Acalypha wilkesianaMuell. - Arg.

Liliaceae Cordyline terminalis (L.)Kunth

Malpighiaceae Malpighia glabra L.

Common Name

hemigraphis

carpet-weed

mango

allamanda

anthurium

panax

orange trumpet vine

canna

papaya

Maui pamakani

Spanish needle

sweet potatobeach morning-glory

balsam apple

copper leaf

ti

acerola

TABLE III. Continued

Fanlily Species

Ma.lvaceae Hibiscus rosa-sinensis (L.)Thespesia populnea (L.)

Sol. .

Meliaceae SWietenia mahagoni (L.)Jacq.

MiInosaceae Prosopis pallida (Willd.)HBK

Myrtaceae P sidium guajava L.

Orchidaceae Dendrobium.~Arundina. bambusuoHa

Lindl.

Palm<:+e Rhapis excelsa (Thunb.)Henry

Passifloraceae Passiflora foetida L.Passiflora edulis f.

flavicarpa Degener

Rubiaceae Coffea arabica L.

Rutaceae Citrus :paradisi Mad.Citrus sinensis (L.) OsbeckCitrus limonia OsbeckMurraya exotica L.

Sapindaceae Litchi chinensis Sonne

Solanaceae Solanuxn sodoroeum. L.

Verbenaceae Clerodendrum fragrans(Vent.) R, Br. var.pleniflorum Schau.

Lantana. ca.mara L"Lantana. montevidensis

(Spreng.) Briq.

12.

Common Name

hibiscusmi1p._

mahogany

kiawe

guava

dendrobiumbamboo orchid

bamboo palm

running popyellow passion fruit

coffee

grapefruitsweet orangelemonmock orange

litchi

apple of sodorn

glorybower

lantanatrailing lantana

13.

remains the possibility of recording plants which are merely

accidental hosts because of the general prevalence of!!.. phoenicis

in some areas.

Although ]h ;phoenicis and !!.. obovatus are polyphagous and

infest m.any kinds of plants in common, there are some plants which

support only one of them. The garden violet, Yl2.!! odorata L., was

found by Morishita (1954) to be a practical host for laboratory rearing

of B. obovatus; however, in this study, it was found unsuitable for

rearing .!!a. phoenicis. Likewise, 14 oboyatus was not able to re!1"0­

duce on papaya which proved to be an excellent rearing medium for

~ phoenicis. These two plants, the garden violet and papaya, may

be used in the separation of mixed populations into pure cultures of

these two species of mites which coexist on many kinds of plants and

are extremely difficult to distinguish unless mounted and examined at

magnifications of 900X or higher.

14.

METHODS AND MATERIALS

Stock cultures of B. phoenicis were started from field collected

specimens found infesting papaya in Manoa Valley, Oahu, Hawaii, on

April 25, 1962. The mites were mass reared on potted papaya plants,

three to five months old, which were kept outdoors but sheltered

from wind and rain. As needed, the mite s we re transferred from

these source plants to rearing media in order to study the various

aspects of the biology and control of this species of mite.

Since papaya of the Solo variety is of great economic itnport­

ance and a favorable host plant of B. phoenicis, it was used to study

the life history of this species in the laboratory. Green papaya fruits

or sections thereof were used as rearing media for they remained in

fairly good condition long enough to allow the completion of a life cycle

and were easier to manipulate under laboratory conditions than other

types of media. Excised leaves and stems of most plants used as

rearing media required frequent changing due to rapid desiccation.

This was especially true when mites were reared on them at tempera­

tures above 2SoC and at relative humidities below 60 per cent. The

necessity of frequent changes of the medium created a risk of injur­

ing or 10 sing the mite s while making the transfer s to fre sh medium.

When using papaya fruits under these adverse conditions, the entire

surface, except for the areas where the mites were allowed to feed,

was coated with paraffin. The paraffin film helped to prevent the rapid

15.

desiccation of the fruits by reducing the surface area of transpiration.

For transferring mite s from stock culture s to rearing m.edia,

a human hair mounted on a wooden handle of a dissecting needle

proved most satisfactory. Although the mites wer'e accidentally

jabbed in the process of picking them up for transference, the hair

was flexible enough so that no bodily harm was inflicted. The tip of

the hair was thrust beneath the venter of the mite from the caudal end

until the entire body came to rest on the hair before lifting it off the

plant surface. SinCE:~. :phoenicis has a strong tendency to move in a

forward direction when disturbed, it was found best to pick up the mite

from the posterior so that the anterior end always faced the tip of the

hair. When the mite was picked up in this position, it crawled off the

hair readily onto the desired area of transference but when picked up

in the opposite position, posterior end facing the tip of the hair, the

mite invariably crawled up the hair towards the handle and made dis­

lodging of it onto the plant surface difficult.

Whole fruits were used as rearing media for the life history

studies of B. phoenicis. lITanglefoot ll was used as a barrier to con­

fine the mites on the fruits. All excess amounts of IITanglefoot ll were

scraped off with an edge of a microscope slide so that only a thin,

slightly tacky film was left along the inner margin and a thicker layer

left along the outer margin of the barrier. When liberal amounts of

"Tanglefoot" were deposited along the inner margin l • the active stages

16.

of the mite invariably crawled into the material and died; however,

when the excess was removed, they were prevented from being caught

in it and also the remaining deposit was sticky enough to discourage

them from walking over it. The thicker deposit of "Tanglefootlt on

the outer margin of the barrier not only provided assurance against

the confined mites from escaping but also prevented other mites from

invading the premises of the individuals under observation.

The life history studies were begun with the egg stage. For

each combination of temperature and humidity condition under which

the life cycle of~ phoenicis was carried out, the mites were confined

in two ways, individually and in mass. When confined individually, tp.e

starting population of 100 eggs was placed on two fruits; 50 eggs to a

fruit, and each egg was allocated an area of 1. 0 sq. cm. on the sur­

face of the fruits. When confined in mass., the 100 eggs were placed

on one fruit in four batches of 25 eggs each. Each batch of eggs was

confined within an area of 4.0 sq. cm. of the fruit surface. The result­

ing larvae from these eggs were allowed to feed and to complete their

protonymphal and deutonymphal stages within the original confines

allocated to them earlier in the egg stage. Upon completion of the

deutonymphal stage, 50 newly emerged females from each tempera­

ture and humidity combination studied were selected; 25 females from

those confined individually and 25 from those cmfined in mass, and

transferred to. fresh fruits. The females that developed from eggs

17.

held individually and in mass were continued to be held in the res­

pective manner until completion of the life cycle. The eggs deposi­

ted by these females were counted and transferred from the fruit

surface onto 2. 0 cm. x 6. 0 cm. strips of adhesive tape on each ob­

servational date. These eggs were exposed to the same temperature

and humidity conditions as the females which laid them to determine

thei.r 'h::otchability.

The fruits with the eggs confined on them were enclosed inside

of wide-mouth gallon jars and placed in constant tem];erature cabinets

for rearing. Within each jar, the fruit, together with a temperature

and humidity indicator (Airguide), were placed on top of a wire screen

platform which was elevated about 8.0 cm. above the bottom of the

jar (Fig. 2). Also, in the bottom of each jar, 650 cc. of a saturated

salt solution was added in order to maintain· the desired level of

humidity within the closed system. The salts used to obtain the follow­

ing levels of relative humidity: 25 to 30 per cent, 65 to 70 per cent,

and 85 to 90 per cent, were potassium acetate, ammonium nitrate,

and potassium nitrate, respectively.

A modified refrigerator and a commercial incubator were used

as temperature cabinets. These cabinets were held in an air con­

ditioned room where the temperature varied between 2loe and 240 e

and humidity between 60 and 70 per cent. The modified refrigerator

was used for temperatures below Z50 e and the incubator for

'"

Figure 20 Rearing unit used in the constant temperatureand humidity experiments.

180

19.

temperatures of 2SoC and above. Both of these cabinets were

equipped with thermo-regulators and thermostats of:l: O. SoC sensi­

tivity. The thermo-regulator of each cabinet was adjusted and set to

the desired constant temperature with the aid of thermocouples and

a potentiometer. A mercury-in-glass thermometer was placed inside

each cabinet and this, together with the temperature and humidity

indicators enclosed within the jars, were referred to each day to in­

sure that the relative humidity and temperature were maintained

relatively constant throughout the life cycle of the mites.

Once the mites were placed in the cabinets, they were taken out

only briefly whenever necessary to observe and record the various

life history events. Those mites which were confined individually

were taken out from the cabinets at least three times daily for about

lO minutes each time in order to obtain the necessary data for deter­

mining the stadia of the different life stages, the preoviposition period

and fecundity of the females, and the other aspects of the life history.

Those mites which were held in mass were taken out not more than

once a week. Comparison of the survival populations from those con­

fined individually and in mass revealed that isolation as well as the

frequent removal of the individually confined mites from the constant

temperature and humidity conditions to laboratory conditions had no

significant effect on the survival potential of~ phoenicis.

20.

Sections of papaya fruit embedded in agar were used as rearing

media for the chemical control studies of B. phoenicis. This type of

rearing medium as shown in Figure 3 was prepared as follows: A

2 per cent agar solution was heated to the boiling point and then poured

into an aluminum foil tart plate, 8.0 cm. in diameter, until filled to a

depth of approximately 1. 0 em. After the agar solidified, a piece of

papaya fruit, about 5.0 cm. in diameter, was placed cut surface down

in the center of the plate. Then, more agar solution, first cooled to

45 0 C, was poured until about one-half of the original surface of the

papaya section became embedded. The agar provided moisture and

kept the papaya section fresh for two weeks under conditions of 21 0 C

to 240 C and 60 to 70 per cent relative humidity and also served as an

effective escape barrier against the active stages of B. phoenicis.

Mites were transferred from the stock cultures onto rearing media

of thi s type a day prior to subjecting them to the different pesticides

shown in Table VI. Twenty-five females were placed on each plate

and four such plates, or 100 individuals, made up each treatment.

Of the active stages, only the adults were selected for exposure to

the different treatments for in preliminary studies they proved to be

more tolerant of these pesti,cides than the larvae and nymphs.

A settling mist tower which was improvised by Sanchez and

Sherman (1963) was used to apply the pesticides. The four plates of

each treatment were placed on the turntable which revolved around a

¥igure 3. Rearing unit used in the chemical control studies ofBrevipalpuB~~ (Geijskes)

Nt-4•

22.

Venturi tube through which 5.0 cc. of a pesticide was blown under

pressure of about 50 p. s. i. into the tower as a mist. The mist was

allowed to settle for three minutes onto the plates. These plates,

with the treated mites on them, were held for two weeks in an air­

conditioned room where temperature ranged from 21 0 C to 240 C and

relative humidity from 60 to 70 per cent. Mortality records of the

mites were taken on the first, third, fifth, and seventh day after

treatment, and also on the seventh day all of the living females and

eggs present on the plates were counted. The living females were

removed at that time but the eggs were left in situ until hatching to see

if the pesticide residues on the media were still toxic to kill the larvae

which emerged 10 to IS days after the application of the pesticides.

In addition to the tests with the adults, eggs of B. phoenicis were

also subjected to the different pesticides shown in Table Vill, using

the dip method. Only the higher concentrations of most of the pesti­

cides were used because the lower concentrations gave no significant

kill of B. phoenicis eggs. Each treatment consisted of four repli­

cations of 25 eggs each, or a total of 100 eggs. They were placed on

2.0 cm. x 6.0 cm. strips of adhesive tape and dipped for a minute in

the various pesticides. These treated eggs were held for three weeks

in an air-conditioned room to see if the pesticides had any ovicidal

effect.

Since the effects of some of the pesticides on papaya were

23.

24.

DESCRIPTION OF ~IFE STAGES

The life stages of ~ phoenicis include the egg, larva, proto­

nym.ph, deutonym.ph, and adult. Both sexes are present, but m.ales

are scarce and have not been found in many parts of the world where

this species exists.

lh: phoenicis is a very variable species, but it Can be readily

distinguished in the adult stage from. the other mem.bers of the genus

by having five pairs of dorsolateral hysterosom.al setae and two

sensory rods on tarsus IT (Fig. 9B). The larvae and nym.phs also

have five pairso£ dorsolateral hysterosom.al setae but, unlike the

adults, they have only one sensory rod located posteriodistally on

tarsus IT. Morphologically, the im.m.ature stages of.!h phoenicis

closely resemble those of.!h obovatu.s, and like them., they are sub­

ject to considerable variation in the size and shape of some of the

dorsal setae. The num.ber and arrangem.ent of the setae on the

dorsum. of idiosom.a of the larva, protonym.ph, and deutonym.ph con­

form to tho se of the adult and to the genus Brevipalpus ~'pritchard

and Baker, 1952). Twelve pairs of setae are preaent on the dorsum.;

three pairs on the propodosoma and nine pairs on the hysterosom.ao

The location and nom.enclature of these setae are shown in Figure 4.

The size and shape of the dorsal setae of mo st larvae and nym.phs on

papaya are like those shown in the respective illustrations (Figs. 6,

7, and 8), and as described in the sections on the life stages below.

A I B

I.>W ,..,~ DORSOUIT'ERALHYSTEROSOMALS

:::b DOflSALPROPClO<l8ClMALS

> 'i t. ~ DOR8OC£NTlW.1fYSTEROSOMAI.S

r- ,'\. <~ HUIll£RAL

MEDlOVENTRAL if> >:t 7'PROPOOOSOMAI..

ANTERIOR MEDlOVENTRAL y,...METAPOOOSOMAL

POSTERIOR MEDlOVENTRAL 9'i:,'S \.METAPOOO8OIlIAL

VENTRAL PLATE ,.., f/ I .it /'I

ANAL PLATE ' \ \1\. 'i~ ...( \\1 ~'Je....--'

GENITAL PLATE /Aql h I \0 :'_

~igure 4. Outline drawing of Brevipalpus phoenicis (Geijskes) female showing the location andnomenclature of the setae and plates. Ventral aspect (A) and dorsal aspect (B).

N1.11•

26.

Of the dorsal setae, dorsolateral hysterosomal setae I and II, and

dorsocentral hysterosomal setae ill are most variable in size and

shape. These vary from a tiny, serrate setae to large, broadly

lanceolate, serrate setae similar to dorsal propodosomal setae II and

ill. larvae and nymphs with these large setae were more frequently

encountered on passion fruit and bamboo palm than on papaya.

DeLeon (1961) found nymphs of most Mexican specimens of.!!:.

phoenicis with the large dorsolateral hysterosomal setae I and II, and

in three collections, nymphs with the dorsocentral hysterosomal setae

nearly as large as the dorsolateral setae.

The location and nomenclature of the setae on the venter of the

idiosoma are shown in Figure 4. The number of setae on the venter

is not constant but increases from four pairs on the larva, five pairs

on the protonymph, seven pairs on the deutonymph to eight pairs on

the adult. These additions take place in the hysterosomal region of

the body. A pair of medioventral opisthosomal setae is present in the

two nymphal and adult stages but not in the larval stage. The medio­

ventral propodosomal setae, which are present in the larval, nymphal

and adult stages, and the posterior medioventral metapodosomal

setae, which are present only in the deutonymphal and adult stages,

are filamentous and smooth. The remaining ventral setae are short

and smooth.

The following descriptions of the life stages are based on

27.

individuals reared on papaya. All observations and measurements

were made on at least 25 individuals of each stage. Measurements

were taken on living spedmens since mounted ones often undergo con-

siderable distortion in size. Mites were placed on adhesive tape, to

keep them quiescent, and measured under 300 times magnification

using incident light. The width measurements of the larvae, nymphs,

and adults wer e taken at the level of the humeral setae, and the

length taken between the distal ends of the rostrum and opisthosoma

(Table IV). The meaSUremeI:lts shown for the larva, protonymph, and

deutonymph were taken on the inactive phases and represent the

average maximum size attained by individuals in the respective sta-

dium. The average minimum size for each stage is the same as the

measurements given for the stage preceding it.

TABLE IV. AVERAGE MEASUREMENTS OF THE LlFESTAGESOF BREVIPALPUS PHOENICIS (GEIJSKES)

StageLength (mm)

Mean S. D.Width (mm)

Mean S. D.

EggLarva, inactiveProtonymph, inactiveDeutonymph, inactiveAdult, female

0.1080.1710.2320.3080.308

0.0040.0050.0050.0080.007

0.0700.1090.1400.1630.163

0.0040.0040.0040.0050.004

S. D. = Standard deviation.

28.

The egg (Fig. 5) is elliptical and about 0.100 to 0.116 mm. long

and 0.060 to 0.080 mm. wide, averaging 0.108 I:. 0.004 mm. in length

and 0.070 I: 0.004 mm. in width. It is light orange, soft, and very

sticky when first laid. At this time, the egg adheres readily to any

surface it comes in contact with and attempts to remove it usually

result in its breakage. After a few minutes of exposure to air, it be­

comes firm and bright reddish orange. The chorion is thin, trans­

parent, and made up .of at least two layers. The outer layer is drawn

out to a fine stipe on the end of the egg which emerges last from the

ovipositor. This stipe is variable in length and is often missing for it

can be easily broken off by the mites trampling over it. The stipe is

also inconscpicuous in some cases for it bends back and adheres to the

surface of the main portion of the egg. When the egg is viewed under

450 times magnification with incident light, many close set irregular

striae are visible on the chorion; however, when it is mounted in

Hoyer's medium, the outer layer together with the stipe are dissolved

away and the clear, smooth, inner layer becomes exposed.

The protoplasm, which is translucent light orange when the egg

is first laid, completely fills the inside of the chorion and is in close

contact with it. With the advancement of the incubation period, a

space between the developing embryo and the chorion is formed. The

egg becomes opaque white a day before eclosion. The larva and its

,Figure 5. Egg of Brevipalpu6 phoenicis (Geijskes).Enlarged approximately 409 times.

29.

30.

bright red eyes are visible through the translucent white chorion at

this time.

larva

The hexapod larva (Fig. 6) is bright orange-red when newly

emerged and 0.128 to 0.140 mm. long and 0.080 to 0.096 mm. wide,

averaging 0.135 I:. 0.004 mm. in length and 0.088 I:. 0.005 mm. in

width. When fully grown and ready for molting, it is opaque orange

and 0.171 I:. 0.055 mm. in length and 0.109 I:. 0.004 mm. in width.

Two pairs of red eyes are present on the lateral margins of the pro­

podosoma. EKcept for the suture between the propodosoma and the

hysterosoma, and the irregular, folds along the lateral margins of the

idiosoma which gradually disappear as the larva grow, there are no

characteristic integumental markings on the dorsum. The integument

on the venter of the idiosoma, however, has regular parallel striae;

transverse on the propodosoma and anterior portion of the opisthoso­

ma, and longitudinal on the metapodosoma and laterad of the anus.

On the dorsum, the propodosomal setae II and ill, humeral

setae, and the dorsolateral hysterosomal setae ill and V are serrate,

broadly lanceolate, and O.OIl to 0.014 mm. long and 0.004 mm.

wide. The dorsolateral hysterosomal setae IV are filiform, 0.042

mm. in length, and the remaining dorsal setae are serrate and

short, less than 0.004 mm. (Fig. 6).

;Figure 6. larva of Brevipalpus phoenicis (Geijskes).Dorsal aspect. Enlarged approximately364 times.

31.

32.

On the venter of the idiosoma, four pairs of pilose setae are

present; a pair of long medioventral setae on the propodosoma, a pair

of short medioventral setae on the metapodosoma, and two pairs of

short anal setae on the opisthosoma.

Protonymph

The protonymph (Fig. 7) differs from the larva essentially in

being larger and in possessing four pairs of legs. Scattered light

green, orange, black, and yellow patches, resulting from accumu­

lations of food and waste matter inside the body, can be seen through

the translucent integument of the idiosoma. The protonymph grow s

from a minimum size of 0.171 mm. to a maximum size of 0.244 mm.

in length and from 0.109 mm. to O. 148 mm. in width, averaging

0 ..2'32 I: 0.005 mm. in length and 0.140 ~ 0.004 mm. in width as an

inactive protonymph. Except for the suture between the propodosoma

and hysterosoma and the few folds which gradually disappear as the

protonymph grows, no characteristic markings are present on the

integument of the dorsum. On the venter, however, there are regular

parallel integumental striae running transversely across the central

portion of the idio soma with the ends bending longitudinally to the

lateral margins. Longitudinal striae are present between the medio­

ventral setae of the propodosoma and the base of the gnathosoma.

On the dorsum p the propodosomal setae II and ill, humeral

setae, and the dor solateral hysterosomal setae ill, IV, and Vare

Figure 7. Protonymph of Brevipalpus phoenicis (Geijskes).Dorsal aspect. Enlarged approximately234 times.

33.

34.

broadly lanceolate and serrate. All of them are about the sam.e size,

0.014 mm. to 0.016 rr..m. long and 0.006 rom. at the widest part.

The remaining setae: propodosom.al setae I, dorsolateral hystero­

somal setae I and II, and dorsocentral hysterosomal setae I, II, and

m, are serrate and very small, less than O. 004 mm. long (Fig. 7).

On the venter of the idiosom.a, there are five pairs of pilose

setae; one pair of medioventral setae on the propodosoma, metapodo­

soma, and the opisthosoma. The setae on the propodosoma are long,

I 0.028 mm. to 0.031 mm.., while those on the m.etapodosom.a and

opisthosoma are short, O. 004 mm. to o. 006 rom. Two pairs of setae,

similar in length to the medioventral opisthosomal setae, are present

on the anal sc1erites.

Deutonymph

The deutonymph (Fig. 8) is similar to the protonymph in color,

dorsal chaetotaxy, and in the pattern of the st riae on the venter of the

idiosoma. In this stage, two additional pairs of pilose setae are

present on the venter of the idiosoma: a pair of long posterior medio­

ventral metapodosomal 'Setae, 0.031 mm. long, and another pair of

short setae, 0.006 mm., near the anterior margin of the anus similar

in size and shape to those located below on the anal sc1erites. When

fully grown and ready to molt, the size of the deutonymph ranges from

0.292 mm. to 0.324 mm. long and 0.156 to O. 168 mm. wide, averaging

Figure 89 Deutonym.ph of Brevipalpus :phoenicis (Geijskes). Dorsal aspect (left). Ventralaspect (right). Enlarged approximately 263 times.

W\J1•

36.

0.398 1:. 0.008 m.m.. in length and 0.163 1:. 0.005 mm.. in width.

Female

The female (Fig. 9) ranges in size from 0.288 rom. to 0.312

m.m... in length and 0.156 rom. to 0.176 mm.. in width, averaging

0.302 t 0.007 rom. in length and 0.162 t 0.004 rom. in width. The

body coloration of the females is very variable. Differences in age,

food, and temperature conditions have great influence on body color­

ation. In newly emerged females, the area between the red eyes is

bright orange and the remainder of the idio soma is translucent light

yellow with a few brownish patches occurring mediolaterally on the

hysterosoma. When feeding begins, a conspicuous black pattern in

the shape of an "Hit appears on the idiosoma (Fig. 10E to H). The

black pattern enlarges, coalesces, and covers almost the entire

idiosoma of some individuals (Fig. 101). This black pattern gradual­

ly disappears and the females once again assume a uniform carmine

body color a few days prior to death. Females reared at a tempera­

ture of 300 C have a uniform carmine body color and those reared at

200 e and 250 e usually have the black patterns on the idiosoma.

Females on passion fruit are mostly reddish orange and have less

variations in body coloration than those on papaya (Fig. lOA to 1).

On the dor sum, the integument has reticulations mediolaterally

on the propodosoma and hysterosoma. A pair of pores are present..

Figure 9. Female of Brevipalpus phoenicis (Geijskes). Dorsal aspect (A) palpus (B)tarsus IT (left). Ventral aspect (right). Enlarged approximately 300 times. UJ

-.:I•

E

38.

Figure 10. Variation in color patterns of females ofBrevipalpusphoenicis (Geijskes).

39.

mediolaterally on the propodosoma and metapodosoma. Propodo-

somal setae I, II, and ill, humeral setae, and do-rsolateral hystero-

somal setae I, II, ill, IV, and V are narrowly lanceolate, serrate,

and less than 0.010 mm. in length. The three pairs of dorsocentral

setae are minute at;ld setiform.

On the venter of the idiosoma, the reticulations on the ventral

plates and area directly anterior to them are wider than long and

those laterad to them are longer than wide. Eight pairs of pilose

setae are present: a pair of medioventral propodosomal setae, two

pairs of medioventral metapodosomal setae, a pair of setae on the

ventral plate, and two pairs each on the genital and anal plates. The

medioventral propodosomal and the posterior medioventral metapo-

dosomal setae are filamentous and about 0.070 mm. long. The pair

of anterior medioventral metapodosomal setae and those on the ven-

tral and genital plates are similar in length and about one-fifth the

length of the posterior medioventral metapodosomal setae. The anal

setae are the shortest of the setae on the venter and about one-half

the length of the genital setae.

Male

The male (Fig. 11) is wedge-shaped in outline and flattened in

profile. The idiosoma is reddish and has no black marldngs like

those on the females.

40.

On the dorsum, two transverse sutures demarcate the propo­

do somal, metapodosomal, and the opisthosomal regions of the body.

The integument has rather even reticulations mediolaterally and ir­

regular reticulations mediodorsally on the propodosoma, metapo­

dosoma, and the opisthosoma. A pair of pores is present on the

propodosoma and the metapodosoma. The dorsal chaetotaxy is

similar to that of the female.

On the venter of the idiosoma, reticulations are present medio­

laterally along the bases of attachments of legs il, ill, and IV, on the

opisthosoma, and medioventrally along the posterior margin of the

metapodosoma. The medioventral propodosomal and the posterior

medioventral metapodosomal setae are filamentous and very long,

0.070 mm. or more in length. The anterior medioventral metapo­

do somal and the medioventral opisthosomal setae are pilose and very

short; the former about one-fifth and the latter about one- sixth the

length of the posterior medioventral metapodosomal setae. Three

pairs of short, very narrowly lanceolate, and serrate setae are

present on the genito-anal sc1erites.

Figure 11. Male of Brevipalpus phoenicis (Geijskes). Dorsal aspect (A) palpus (left).Ventral aspect (right). Enlarged approximately 300 times.

II:>-J-004.

I'··.···.·········,

42.

LIFE HISTORY

The following is the life history of B. phoenicis based on infor-

mation ob~ined from laboratory rearings conducted under different

levels of relatively constant temperature and humidity conditions.

These two physical factors have been shown to greatly influence the

developmental and reproductive rates of several species of mites

(Morishita, 1954; Boudreaux, 1958; and Nickel, 1960). The purposes

of this life history study were to determine the approximate tempera-

ture and humidity combinations which favor natality and their ranges

which the various stages of B. phoenicia can tolerate. It is hoped

that the information obtained from this study will be helpful in better

understanding the other biological aspects of this mite. Food and

space were kept constant and provided in adequate amounts so as to

minimize intraspecific competition for them. In addition, other

factors that could influence the life history of~ phoenicis, such as

natural enemies and interspecific competition, w:ere excluded in the

present study.

Egg Stage

The egg is deposited in any position in cracks, crevices, exuviae,

and other protected niches on the plant surface. It is laid singly but

since the females tend to reuse the same ovipositional sites, many

eggs are often clustered together. These clusters of bright reddish

orange eggs are more readily seen with the unaided eye than the other

stages of the mite. When an egg is ready for ec1osion, one end 01' ~!

becomes swollen due to the larva pushing against the inner wall of the

chorion with its rostrum. With incident light and at magnifir3tions of

300X or higher, the larva can be seen repeatedly clawing tn€' h~!lel" waH

of the chorion with its front pairs of legs as if tTying to malt€' <In 0pE'n­

ing for emergence. After a while, the chorion splits ~l"tlv around on".

end of the egg at approximately the level of clawing. The larva &t~_ '':>ll

out one of its front legs through the split and uses it to enl~u'ie the

opening further. The larva then emerges anterior end first a.nd in itw:

process pushes aside one end of the chorion which remains conflened

like an "hinged door" to the remainder of the chorion. The empty

transparent chorion remains attached to the plant surface for a long

time unless forcibly removed.

The eggs were found to be greatly affected by the prevailing tt>!1:;-

perature and humidity conditions. Their incubation period and ha.td~··

bility varied significantly between the different temperatures inespE'i.:­

tive of humidity conditions; however, between humidity levels of 63 t(.)

70 per cent and 85 to 90 per cent at a given temperature, they wert':'

essentially the same (Table V). Within each temperature. hatchabil.ity

was lowest at the 25 to 30 per cent humidity level and the incubation

period about a day longer than at the higher levels of humidity. The

minimum incubation period was 8.0 days at 30°C in combination with

65 to 70 per cent relative humidity and the ma.'timum 24.8 days at ZOoC

in combination with 85 to 90 per cent relative humidity. Under the

43.

stages of the mite. When an egg is ready for eclosion, one end of it

becomes swollen due to the larva pushing against the inner wall of the

chorion with its rostrum. With incident light and at magnifications of

300X or higher, the larva can be seen repeatedly clawing the inner wall

of the chorion with its front pairs of legs as if trying to make an open­

ing for emergence. Mter a while, the chorion splits partly around one

end of the egg at approximately the level of clawing. The larva sticks

out one of its front legs through the split and uses it to enlarge the

opening further. The larva then emerges anterior end first and in its

process pushes aside one end of the chorion which remains connected

like an "hinged door" to the remainder of the chorion. The empty

transparent chorion remains attached to the plant surface for a long

time unless forcibly removed.

The eggs were found to be greatly affected by the prevailing tem-

perature and humidity conditions. Their incubation period and hatcha­

bility varied significantly between the different temperatures irrespec­

tive of humidity conditions; however, between humidity levels of 65 to

70 per cent and 85 to 90 per cent at a given temperature, they were

essentially the same (Table V). Within each temperature, hatchability

was lowest at the 25 to 30 per cent humidity level and the incubation

period about a day longer than at the higher levels of humidity. The

minimum incubation period was 8.0 days at 30 0 C in combination with

65 to 70 per cent relative humidity and the maximum 24.8 days at 20 0 e

.in combination with 85 to 90 per cent relative humidity. Under the

TABLEV o EFFECT OF TEMPERATURE AND HUMIDITY ON THl(GEUSKES)

Stage R E L A T I V E&: 25 to 30 Per Cent 6!

Temperatur e Duration (days) I

°c N Range MeantS. D. N Rani

Starting N 100 100(Egg)

~20 5 21.4-23.4 23.0iO.2 67 19.8·25 8 8.7-12.6 11. 1~I. 1 88 9. I·30 0 27 8. o·

Larva20 No survivors beyond 65 9.8·25 egg stage 88 4.8·30 26 3. 1·

Protonymph20 59 7.8·25 87 4.530 26 2.6

Deutonymph20 50 3.525 85 4.730 25 3.5

Immature StageEgg to Adult20 50 17.425 85 23.130 25 16.5

Adult, FemalePreovipo sition20 25 3.225 25 2.130 16 7.0Fecundity20 25 525 25 4130 25 0Longevity20 25 13.425 25 21. C30 25 3. e

~ ON THE,DIFFERENT STAGES OF BREVIPALPUS PHOENIGIS

44.

[)

lVE HUMIDITY65 to 70 Per CentDuration (days)

Range MeantS. D. N

100

85 to 90 Per GentDuration (days)

Range MeantS. D.

7 19.8-24.6 22.2Jl.l 65 18.8-24.8 22.61:.1. 18 9.1-13.0 9.4~0.6 85 8.0-12.9 9.4tO• 87 8.0- 9.0 8.2/:.0.4 29 7.8- 9.2 8.4tO• 9

5 9.8-12.4 10.5~0.7 62 9.5-11.9 10.4tO• 58 4.8- 8.9 6.71:.0.8 83 5.8- 7.8 6.5~0.7

6 3.1- 4.5 3.6.J.0.2 27 3.6- 4.5 3.71:.0.4

9 7.8- 9.5 8.21:.0.7 60 7.7-10.2 8.4/:.0.97 4.5- 9.6 6.31:.0.9 83 4.0- 9.6 6. 5~1. 16 2.6- 3.7 3.11:.0.4 27 2.7- 3.5 3.0JO.5

0 3.5- 4.1 7.51:.0.9 58 2.7,- 4.1 7.3tI.l5 4.7- 9.1 6.8~0.8 83 4.3- 8.2 6.91:.0.55 3.5- 3.9 3.71:.0.5 26 3.8- 4.0 3.91:.0.1

17.4-20.423.1-34.516.5-19.0

48.81:.1.529.31:.0.418.6~0.5

588326

45.4-50.522.0-33.016.8-19.8

47. 7f:.2. 529.31:.1.218.11:.0.2

:5 3.2- 9.5 5. 7tI. 4 25 3.5- 9.0 6.2/:.2.3~5 2.1- 6.7 3.51:.0.9 25 2.3- 6.5 3.71:.0.6[6 7.0- 8.0 7.31:.0.2 14 7.5- 9.0 8.0~0.3

~5 5-29 10.61:.4.5 25 5-20 12.4J5.6~5 41-73 57r51:.10.7 25 8-68 53.3t7.5~5 0-19 6.41:.2.4 25 0-17 7.5~1.7

~5 13.4-72.3 45.8/:.9.7 25 15.0-70.3 47.01:.12.1~5 21.0-44.0 34.81:.6.0 25 25.3-50.0 34.51:.3.5~5 3.8-20.8 10. 5t3~ 7 25 4.5-12.0 7.5J2.0

45.

foregoing conditions, however, only a few of the eggs hatched; 27 per

cent under the former and 63 per cent under the latter conditions.

Optimum hatch of 88 per cent was obtained at 25°C in combination

with 65 to 70 per cent relative humidity; however, the average incu­

bation period in this case was slightly longer than that at 300C with

the same level of humidity but the majority of the eggs hatched in 9.4:1:

0.6 days or less than one-half the time required by those subjected to

20°C. Some eggs hatched at 20°C and 25°C in combination with all

three levels of humidity, but at 30°C, hatching occurred only at the

65 to 70 per cent and 85 to 90 per cent levels and none hatched at the

25 to 30 per cent level.

None of the eggs hatched when exposed for several days to con­

stant temperatures below 20°C and above 30°C in combination with

either high or low humidity. The eggs maintained the shape and color

of freshly laid ones for about a month at temperatures below 20°C but

they became shriveled and opaque white in about four days at tem­

peratures above 32°C, especially when humidity was low.

Although continuous exposure of eggs to 20°C and 30°C caused

considerable reduction in hatchability, an exposure of 24 hours first

to either of these temperatures and then maintaining them at 25°C

with 65 to 70 per cent relative humidity had no detrimental effect on

hatchability. However, when temperature was decreased below 20°C

and increased above 30°C, short exposures caused hatchability of eggs

46.

to decline gradually in the former and abruptly in the latter case.

Hatchability of eggs which were first exposed to the different high and

low temperatures for 24 hours and then maintained at 250 C in combi­

nation with 65 to 70 per cent relative humidity, declined from 89.5:1:

3. 0 per cent at 300 C to 45.0:1: 5. 5 per cent at 320 C to O. 0 per cent at

340 C or a 100 per cent reduction in a temperature change of only four

degrees; but at the low temperatures, it declined from 87.5 :I: 4.5 per

cent at 200 C to 41.0 :I: 4.5 per cent at 150 C to 27.5 :I: 6.0 per cent at

100 C or a reduction of some 68 per cent in ten degree change in tem­

perature.

Immature Stages

The larva, protonymph, and deutonymph each spends about one­

half of its stadium as an active and one-half as an inactive individual.

Feeding, growth, and limited dispersion take place during the active

phase and transformation into the subsequent stage during the inactive

phase. Prior to becoming inactive, the mite assumes a characteristic

position. The chelicerae are fully extruded and inserted into the plant

tissue; the front two pairs of legs are extended straight forward and

drawn close to each other; and the posterior legs, one pair in the case

of the larva and two pairs in the case of the nymphs, are extended

straight backwards and held close to the sides of the opisthosoma.

This characteristic position was assumed to be the ending of the active

and the beginning of the inactive phase of each stage. Although the

47.

chelicerae are inserted in the plant tissue during the inactive phase,

they are not used for obtaining nourishm.ent but are used for an-chor­

ing the body in place. Besides using the chelicerae for anchoring,

an adhesive substance is apparently secreted by the mite just prior

to becoming inactive for the entire ventral surface of the body is

fastened to the plant surface as though glued and prying is needed to

dislodge an inactive mite. Ecdysis progresses normally even though

such a mite is dislodged soon after becoming inactive but the sub­

sequent stage has some difficulty in freeing itself from the exuvium

at the time of molting. When an inactive larva is mounted in Hoyer's

medium and examined under 300X or better magnification with trans­

mitted light, the outline of the developing protonymph can be seen

inside the exo skeleton of the larva. Leg s I, II, and III of the proto­

nymph are held inside the corresponding legs of the larva but since

the latter has only three pair s of legs, legs IV of the former are held

free along each side of the opisthosoma.

The habits of all the immature stages are similar except feed­

ing, growth, and disper sion become more pronounced with. the

passing of each stage. The newly emerged larva wander s in the im­

mediate vicinity of the chorion from which it has emerged for about

an hour before commencing to feed while the newly emerged proto­

nymph and deutonymph move further away from their exuviae and

com.m.ence feeding almost im.rn.ediately. The feeding damage done by

48.

the larva is hardly noticeable but that inflicted by the later stages is

readily discernible for the imm.ediate area around each feeding

puncture becomes discolored and blisterlike soon after the insertion

of the chelicerae (see page 57 for further descriptions of feeding

dam.age). The larvae and nymphs seldom leave the area where they

had emerged from the egg stage. They feed avidly and grow rapidly

during the active phase and undergo transformation just as rapidly dur­

ing the inactive phase when environmental conditions are favorable.

The temperature and humidity conditions favoring egg hatch also

proved suitable for larval and nymphal survival. At 250 C in combi..

nation with 65 to 70 per cent relative humidity, conditions under which

optimum hatchability was obtained, the majority of the newly emerged

larvae successfully passed through the three immature stages in

19.8 f:. 0.9 days. Development of the immature stages from egg hatch

to adult emergence was most rapid at 30°C, 10.6 t 0.3 days, and

slowest at 20oC, 27.3 t 1.7 days. Some individuals successfully

reached the adult stage under constant temperatures of 200C, 25°C,

and 30°C in combination with either 65 to 70 per cent or 85 to 90 per

cent relative humidity, but none survived beyond the larval stage when

humidity was 25 to 30 per cent (Table V). Except for the temperature

and humidity combinations of 25°C with 65 to 70 per cent and 85 to 90

per cent at which more than 80 per cent of the starting population suc­

cessfully completed the egg, larval, and the nymphal stages, the other

49.

combinations caused high larval mortality in addition to the low egg

hatch so that less than 35 per cent of the starting population reached

the adult stage. But once passed the larval stage, the protonymphs

reached the adult stage without much mortality for the nymphs were

more tolerant of the adverse conditions than the earlier stages

(Table V).

oProlonged exposures to temperatures above 30 e and below

200 e were fatal to the immature stages regardiess of humidity condi-

tions. The larvae died within two days after being exposed to 320 e,

whereas they became motionless, ceased to develop beyond that stage,

and remained alive for at least 10 days when exposed to 180 e. Some

larvae remained alive for as long as a week at temperature as low as

100e and when transferred to favorable temperature and humidity

conditions, 250 e in combination with 65 to 70 per cent relative

humidity, they continued development.

Adult Stage

The adult stage was reached in I~. 6 i. 0.5 days at 300 e and in

48.8 I:. 1.5 days at 20 0 e after the eggs were laid. At these extremes

in temperature, only few of the starting population of eggs success-

fully reached the adult stage despite favorable humidity conditions

(Table V). Completion of the life cycle was not possible when tem­

perature was above 30 0 e and below 20 0 e regardless of humidity

conditions, and when humidity was only 25 to 30 per cent regardless

50.

of temperatur'e conditions. Survival was highest at 250 C in cOUlbi­

nation with either 65 to 70 per cent or 85 to 90 per cent relative

humidity as 85 and 82 individuals reached the adult stage out of each

of the starting population of 100 eggs, respectively. All of the adults

that were reared from the egg stage under the different temperature

and humidity combinations were females, and thus, the discussion that

follows on the various life processes of the adult stage is on the

female sex.

Preoviposition Period: The female starts to feed soon after freeing

herself from the deutonyxnphal exoskeleton and must feed before egg

laying can comm.ence. This period between emergence and deposition

of the first egg, referred to as the preoviposition period, wa,s as

shown in Table V for the different temperatures in combination with

65 to 70 per cent and 85 to 90 per cent relative hwnidity. Although

the durations of all life processes discussed thus far, such as eclo­

sion, ecdysis, life cycle, etc.: were shortest at 30oe, the preovi­

position period was longer at this temperature than at 200 e and

250 e. Moreover, continuous exposure to 300 e probably affected the

reproductive physiology in the early stages of development for many

of the females failed to lay any eggs even though they were trans­

ferred to more favorable temperature and humidity conditions soon

after reaching the adult stage. Females in which the earlier stages

51.

were exposed to constant temperature of 25 0 C, however, started to

lay eggs earlier when exposed to 300 C soon after becoming adults

than those kept continuously at 250 C from the egg stage to the end

of the preoviposition period.

Oviposition: When ready for oviposition, the female locates a suit­

able site such as an exuvia, crack on the plant surface or a bud axil

for depositing the egg. She first examines and cleans out all debris

from the site with the front pair of legs, turns herself 180 degrees so

that the tip of the opisthosoma now is in contact with the ovipositional

site, and then deposits the egg after about a minute of alternate con­

tracting and expanding of the body. After depositing an egg the female

leaves the oviposition site and resumes feeding in its proximity until

the next egg is ready for deposition some six hour s later at the earli­

est, at which time she usually returns to the former site to deposit

it. Because of this habit of returning to the same site for oviposition

and since many females frequently oviposit in a common site simul­

taneously, several eggs are massed together even though only one

egg is laid per individual during an extended duration. The female

seldom wandered afar but remained within the confines of the original

area in which she was reared as long as food was ample and suitable.

When intraspecific competition for food and space became intensive

due to overcrowded conditions, the females emigrated to uninfested

52.

parts of the same plant or to other plants and continued feeding and

oviposition.

The number of eggs laid by the females varied greatly with

temperature differences when humidity was kept constant (Fig. 12

and Table V). At 25 0 C, all of the females began laying eggs and con­

tinued to lay from one to four egg s per day per individual during their

life span. One of the females laid a maximum of 76 eggs in 42 days

of existence and these were deposited equally during the day and night

without any peak periods of oviposition. Out of the 562 eggs laid

during a 24-hour period by 300 females which were kept under con­

stant temperature of 25uC in combination with 65 to 70 per cent

relative humidity, 271 were deposited between 8:00 a. m. and 8:00

p. m. and 291 between 8:00 p. m. and 8:00 a. m. These eggs were de­

posited uniformly throughout the day and night without any peak hours

of oviposition. Oviposition was very irregular at 200 e and 300 C and

it ceased at temperatures below and above these temperatures, res­

pectively. All of the females laid some eggs at 20 0 e but over 50 per

cent of them failed to lay eggs at 30oe. At these two temperatures,

the number of eggs laid per female was less than one-fifth the num­

ber laid at 250 C. When gravid females were subjected to tempera­

ture of 18oC, they laid no eggs as long as they were held at this

temperature, but when returned to 25°C, they commenced to lay

eggs again after 8 to 10 hours. Some females survived exposure to

53.

Z<lW:E

2 3 4 II 8

WEEKS7 8 9 10

,Figure 12. Mean number of eggs laid per week by four startingpopulations of 25 Brevipalpus phoenicis females.

54.

constant temperature as low as 100 C for 23 days and wh.en returned to

more favorable conditions, 25°C and 65 t?_ 79 per cent relative humi­

dity, they started to lay eggs after a day.

Longevity: Some of the more obvious factors which affected the

longevity of the adults were food, temperature, and humidity. When

food was withheld, the adults died from. starvation within three days.

The adults were m.ore susceptible to temperature changes than to

humidity changes and they tolerated the changes better than the im.­

mature stages. The adults lived longer under tem.perature conditions

below 25°C than above it (Fig. 13 and Table V). The average longevi­

ty was 47.0 t 12.1 days at 20°C but only 7.5 t 2.0 days at 30°C in

com.bination with 85 to 90 per cent relative humidity. At 30°C, less

than 25 per cent of the adults were alive at the end of two weeks

while 75 per cent of them were still alive at the end of five weeks at

20°C. Although the females lived longer at 20°C than at 25°C, they

laid only a few eggs, remained quiescent m.ost of the time, and

caused very little feeding injuries. At 2SoC in com.bination with 65

to 70 per cent relative hum.idity, the m.ajority of the fem.ales lived for

over a m.onth, laid m.ore eggs than at other temperature and humidity

com.binations, and oviposition continued daily up to a day prior to

death.. For each respective decrease and increase in temperature

below 20°C and above 30°C, longevity of the adults shortened at a

55.

faster rate at the high than at the low tem.perature levels. At 3ZoC,

none of the adults were alive after 7 days, whereas at lOoe som.e

were still alive after 23 days.

90

80

70>­I-:Jj:!600:::o~

50

I-ZW040

0:::Wa.. 30

20

10

56.

23456

WEEKS7 8 9

Figure 13. Longevity of the adults of Brevipalpusphoenicia (Geijskes) at the differenttemperatures in combination with 65to 70 per cent relative humidity.

57.

BIOLOGICAL OBSERVATIONS

Molting

B. phoenicia, like most other tetranychids, molts three times

during its life cycle; at the end of the larval, protonymphal, and the

deutonymphal stages. In the process of molting, the integument to

be cast off splits transversely across the dorsum slightly in back of

the humeral setae, along the lateral margins of the podosoma, and

transversely across the venter at the level of the frontal margin of

the anus. The emerging mite pushes itself backwards, frees the

front two pairs of legs from inside the exoskeleton of the previous

stage and, in doing so, the exuvia separates into t"w-v sections along

the splits mentioned above. The small posterior section remains

attached to the opisthosoma of the newly emerged mite until rubbed

off and the large anterior section remains attached to the plant sur­

face for a long time and serves as a common site for oviposition.

When the front legs are freed, they are used to withdraw the rest of

the body from the exuvium. The molting process, from the appear­

ance of the split on the dorsum until the emergence of the mite from

the exuvium required from 20 to 45 minutes at 250 C in combination

with 65 to 70 per cent relative humidity.

Feeding

B. phoenicis is an active feeder, feeding at all hours of the day

and night during the greater part of its active phases. Feeding is

58.

especially intense and its resulting damage very extensive when tem­

perature is between 250 C to 30 0 C and relative humidity high. This

species feeds on the stems of many kinds of plants; however, when

high population density prevails, some individuals emigrate to other

parts of the plant. On papaya plants, this mite usually feeds on the

trunk at the l.,vel where the bottom whorl of leaves are attached. As

intraspecific competition for food and space intensifies, the mites

feed upwards on the trunk and outwards onto the leaf petioles and

fruits, leaving a large conspicuous damaged area behind them.

In feeding, the needlelike chelicerae are used to puncture the

epidermal cells. The sap that oozes out from the wounded cells is

mixed with saliva and imbibed into the digestive tract of the mite.

The immediate area around the feeding puncture becomes raised and

blisterlike as though caused by a toxic substance. Later, the affected

tissue dries up, dies and becomes discolored. Since many feeding

punctures occur close together, the affected areas coalesce to form

a large continuous calluslike, tannish, scaly and/or scabby area

(Fig. 14). The feeding damage is very pronounced when young papaya

fruits are attacked for the affected areas become sunken due to the

differential growth of the injured and uninjured tissues. The mites

sometimes puncture the latex glands while feeding, causing a copious

outflow of a milky white liquid which mars the appearance of the

fruit (Fig. IS). All stages of the mite in the path of the flow of the

":-."";""', '..

Figure 14. Feeding injury caused by Brevipalpusphoenicis (Geijskes) on papaya fruit.

59.

60.

sticky latex are engulfed and drowned in it. The stem of papaya

which normally remains green for a long time takes on a tan,

suberized appearance prematurely and makes a spindly growth when

heavily infested by B. phoenicis.

A disease of orange known as Lepra explosiva in Argentina,

originally thought to be caused by a fungus (Marchinatto, 1935) and

later by a virus (Marchinatto, 1938; and Blanchard, 1939), is now

attributed to toxins injected by ~. obovatus in the process of feeding

(Carter, 1952). B. phoenicis has been collected from an orange tree

exhibiting symptoms of Lepra explosiva in Paraguay (Nickel, 1958).

In addition to the feeding injury described above on papaya, B.

phoenicis causes pitting and splitting of the sld.n of orange fruits

(Planes, 1954), scarring of tangerine fruits (Nickel, 1958), galling

of sour-orange seedlings (Knorr, et al., 1960), and defoliation and

vine dieback of passion fruit (Fig. 16).

Mating

Mating is seldom seen because 'of the scarcity of B. phoenicis

males. During the two years of study, only six matings were ob­

served. In every case, the males mated with non-gravid females

about a day old and remained in copula for about 15 minutes. In

mating, the male approached the female from the posterior, rested

his two pairs of front legs on the dorsum of the female's opisthosoma,

Figure 15. Feeding injury caused by Brevipalpusphoenicis (Geijskes) on papaya fruit.Note the exudates from feeding punctures.

61.

Figure 16. Feeding damage caused by Brevipalpus phoenicis (Geijskes)on passion fruit. a­

N.

63.

and crawled beneath the opisthosoma so that one-half of his body was

beneath hers. Simultaneous to crawling beneath the female, the

opisthosoma of the male was bent upward and forward in a form of a

Ilell until the tip came in contact with the posterior end of the female's

opisthosoma. Attached to the female in this position, the male

walked along on his two hind pairs of legs, holding on to the dorsum

of the female's opisthosoma with the front two pairs of legs and fol­

lowed her wherever she went. These mated females produced only

female progenies as did the unmated females under laboratory con­

ditions so it was not possible to find out if the males were functional

or otherwise. Cytological confirmation of this was unsuccessful for

the standard method of chromosome determination using the squash

technique with either aceto-orcein, aceto-carmine or Snow's stains

failed to bring forth the chromosome complement of this species al­

though hundreds of eggs and adults were treated and examined.

Sex Ratio

As stated earlier, males have not been found in many parts of

the world where this species is known to occur. Here in Hawaii,

males comprised less than 1 per cent of the 6, 774 adults collected

from various localities and at different seasons during 1962-63.

There were no indications of seasonal or local abundance of males.

In the laboratory, several generations of.!!.:. phoenicis were reared

without males. No males were obtained from females of all ages

64"

which were reared under the different temperature and humidity con­

ditions. Also, mated as well as unmated females produced only

female progenies. These rearing data, plus the occurrence of pre ..

ponderance of females in nature, indicate that parthenogenisis is the

principal mode of reproduction in this specie s.

Dispersion

Man, in transporting plants from place to pl.ace, has unknowing ..

ly disseminated B. phoenicis to many distant places. The ability of

this mite to subsist on many different kinds of plants has certainly

enhanced its rapid spread and establishment in many tropical areas

of the world.

Within a given area, birds, insects, mammals, wind, and rain

have been incriminated as disseminating agents of many organisms.

Of these, wind has been proven to be the most important agent of

disper sal for many spider mite s (FIe schner, .!:! al., 1956; and Boyle,

1957). Likewise in this study, wind was demonstrated as an impor ..

tant disseminating agent of ~ phoenicis. Several microscope slides

coated with "Tanglefoot" and strips of fly paper were placed at vary­

ing distances from a papaya plant heavily infested with B o phoenicis

and other species of mites. After a 24..hour exposure periodp 123

adults of~ phoenicis and several specimens of Tetranychus

telarius (L.) were trapped on the microscope slides and strips of

65.

fly paper placed directly downwind from the source of infestation.

None was found on those placed upwind from the source of infestation.

The slides and fly papers placed nearest to the source of infestation

contained the greater number of mites. One individual was taken on

a slide placed as far as 50 feet away from the infested papaya plant.

Another common way in which wind may play an important part in

mite disper sal is blowing fallen leaves with mites on them for great

distances. Although B. phoenicis commonly feeds on the stems,

crowded conditions cause many individuals to establish them selves on

the petiole and on the lower surface of leaves along the main veins.

Intensive feeding causes the leaves to drop prematurely and, when

windy, these infested leaves are blown some distances away from the

source plant. Should one of these leaves land fortuitously on or in the

vicinity of a suitable host plant, an incipient mite population can be

started by this means.

Disper sion by migrating from plant to plant by crawling over

non-plant surfaces is unlikely when great distances are involved for

none of the active stages of B. phoenicis are able to live for more

than three days without food. In closely set plants, however, disper­

sion by crawling f:rom plant to plant is possible for under conditions

where plants were sheltered from wind and rain, clean plants became

readily infested when placed near infested ones. Also, many mites

were caught in the sticky bands that were wrapped around the bottom

66.

of the tTunks of both infested. and uninfested papaya plants to study the

migration of B. phoenicis. The bands on the uninfested plants were

adjusted to trap immigrating mites and those on the infested for emi­

grating mites. Emigration of mites from the infested plants started

when the plants became over-populated and suitable feeding areas

scarce. Immigration onto uninfested plants occurred soon after

emigration started; however, the number of immigrants was con­

siderably less than the emigrants. Apparently, many of them died in

the process of finding a suitable host during migration. Plants in

direct contact with the infested plants became infested much sooner

than those somewhat removed from the source of infestation. The

outward migration of mites due to population increase is very evident

on passion fruit for the vines intertwine and form a contiguous mass

of growth. On this plant, B. phoenicia foci of infestation enlarge

concentrically, leaving in their wake a conspicuous feeding damage

characterized by defoliation and vine dieback.

67.

POPULATION STUDIES

Seasonal Abundance

The seasonal fluctuations of the ~ phoenicis population densi­

ties were studied over a two-year period at two localities, Manoa and

Kaneohe, Oahu, Hawaii. Backyard papaya plants in their first year

of fruiting and receiving no pesticidal treatment were used for follow­

ing the monthly fluctuations of the mite populations. The monthly

samples consisted of 40 imprints made with adhesive tapes taken from

10 plants at each locality. Each imprint consisted of an area 6.25

square centimeters of the trunk. The imprints were taken from four

sides of the trunk and between six to ten inches below the attacbm.ent

of the bottom whorl of leaves for here is where the B. phoenicis

populations are usually concentrated.

All stages of ~ phoenicis were present at every sampling date

throughout the two-year period but their numbers varied from month

to month at the two localities. All stages of the mite were numerous

from June to October and scarce from December to May, and were

more abundant in 1962 than in 1963. The monthly densities and fluc­

tuations in the egg and adult populations which were very sim.ilar at

the two localities during the two-year period are shown in Figure 17.

The nUIIlber of individuals, especially the active mites, decreased

suddenly following a heavy rain and increased gradually with the

return of warm and hurm.d conditions. Rain not only ha:m.pered the

68.

III

oII,

POPULAnON

MANOA

0"0I "'0: '0I \I \I \

9 bI \I ,I

1963

KANEOHE

(/)

~200::)o()

0"0"""I V'V'\R J' '\ ./EGG POPULATION

I b-u \~I \I 0I \o \

\\

q P, 0-\ I \'0,\ "',0 ~o b'O

J F M A M J J A SO N OJ F M A M J J A S 0 r'f 0

1962 ' 1963

Figure 17. Egg and adult densities and fluctuations of Brevipalpusphoenicis (Geijskes) populations during 1962 and 1963at Manoa (upper) and Kaneohe (lower). Oahu, Hawaii.

69.

movement of the active mites but washed off many of them from the

plant surface; however, it had little effect on the eggs and the inactive

mites which are more firmly attached to the plant surface. In areas

and during periods of adver se climatic conditions, many of the mite s

were observed feeding on the sheltered sides of sterns, leaves, and

fruits away from direct exposure to sun, rain, and wind.

The number of generations produced at Kaneohe and Manoa

during 1962 and 1963 was impossible to determine because of the great

overlap of the different generations caused by continuous reproduction

throughout the year. However, based on the information obtained

froIn the life history studies conducted in the laboratory, at least 10

generations per year were probably produced in the plots during the

two-year period of study.

We station

B. phoenicis infestations varied between the different kinds of

plants, localities, and seasons. Infestations on papaya were found

at all of the locations on Oahu from. sea level to about 1,000 feet

elevation where this crop is grown extensively. Out of the 350 plants

examined during 1963 at different months of the year, 253 of them

were infested by B. phoenicis. All stages of the mite were present

throughout the year at all of the localities. Older papaya plants of

fruit-bearing age were more heavily infested than younger plants of

700

pre-fruiting age. One of the plants in its f~rst year of fruiting had

3,094 !!:. :phoenicis in all stages of developm.ent within an area of

6.25 square centimeters on the trunk surface, with lesser numbers

on the leaf petioles and fruits. On the fruits, ~ phoenicis infesta-

tions were usually concentrated on the side of the fruit that was in

direct contact with the infested trunk or with another infested fruit.

Those fruits located lower on the trunk were m.ore heavily infested

than the younger fruits and blossom.s closer to the apex of the trunk.

None of the other species of plants studied were as heavily in-

fested by B. phoenicis as papaya. The highest num.ber of l!. phoeni-

cis counted within an area of 6. 25 square centitneter s of stem.- '

surface was 181 on passion fruit, 59 on lem.on, 50 on anthurium., 45

on hem.igraphis, and 8 on hibiscus. On other host plants listed in

Table ill, large am.ounts of plant m.aterial had to be exam.ined before

all stages of~ phoenicis were encountered. Infestations by this

species of m.ite were not found on any of the above-mentioned host

plants when found growing in areas above 2,500 feet elevation where

rainfall is ~bundant and temperature drops below 200 C for many days

out of the year.

71.

NATURAL CONTROL FACTORS

There are many factors or conditions, both biotic and abiotic,

which influence the population density of B. phoenicis in a given area.

Abundance of host plants, warm. and humid climate, and paucity of

natural enemies are some conditions which favor high population

density of this mite, whereas conditions contrary to these tend to

depress it and favor the natural control of the pest. In Hawaii, B.

phoenicis is very abundant in areas between sea level and 1, 000 feet,

scarce between I, 000 and 2, 500 feet, and has never been recovered

from areas above 2, 500 feet in elevation. Since host plants are

abundant in all of the areas, this factor is not the cause of the differ­

ences in population density. However, the laboratory studies

revealed that temperature does greatly affect the reproductive and

survival potential, and this is probably the main factor which causes

B. phoenicis to be of no econom.ic importance in areas above 1,000

feet elevation. Here, temperatures drop periodically to a level where

mortality is considerably greater than natality and completion of a

life cycle is not possible.

Temperature conditions along the coastal areas in Hawaii are

favorable for continuous reproduction throughout the year at nearly

maximum reproductive and survival potential; however s the popula..

tion density of B. phoenicis has never been observed in any locality

to reach the point where food and space become limiting due to

72.

intraspecific competition. Food and space do not become lim.iting

over a whole orchard or locality but can become lim.iting on indivi­

dual plants due to both intra- and interspecific competition. Papaya,

for example, is attacked by at least seven species of phytophagous

mites other than the several species of insects which are of minor

importance (Holdaway, 1941). The mites are: Tetranychus telarius

(L.), Eutetranychus banksi (McGregor), Panonychus~ (McGregor),

Tuckerella pavoniform~s (Ewing), Tuckerella ornata (Tucker),

Hemitarsonemus latus (Banks), and B. phoenicis. !. telarius,

!:h latus, and B. phoenicis are the major pe sts of papaya. Individuals

of these three species have been observed to coexist, increase to

tremendous numbers, and to severely damage individual plants to the

extent that the food media were no longer suitable for the members of

their own species as well as those of the other species. Under such

intense conditions of intra- and inter specific competition, many

individuals of B. phoencis die from starvation and predation by ants,

mites, spiders, and other predators which are fairly common in

Hawaiian soils in the process of migration to other host plants, es­

pecially when great distances are involved. Even though some

individuals of B. phoenicis are successful in reaching a host plant,

it may be already occupied by some other organisms which compete

with this species of mite for the same food and space, or the new host

73.

plant may not be as conducive for population increase as papaya. The

latter is evidenced by the considerably lower infestation indices of

the mite on different kinds of plants mentioned earlier and by the

lower fecundity data reported by authors who reared ~ phoenicis on

plants other than papaya (Planes, 1954; Baptist and Ranaweere, 1955;

Dosse, 1957; and Moutia, 1958).

Within the favorable ranges of temperature and humidity, one of

the most conspicuous natural factors that keeps B. phoenicis from

reaching epidemic proportions is natural enemies. Murna (1958) noted

a strong negative correlation between the summer-fall infestations of

!h phoenicis and a complex of Typhlodromus and Arnblysiopsis on

citrus in Florida. Although actual predation was not observed, he

considered these phytoseiid mites to be the principal cause for the

reduction in infestations of B. phoenicis which undergo cycles of high

and low intensity in Florida. In Hawaii, at least four species of pre-

dators, three mites and an insect, have been observed feeding on

B. phoenicis. These are: Phytoseiulus macropilis (Banks)

(Me so stigrnata: Phytoseiidae), Arnblyseius largoensis (Murna)

(Mesostigmata: Phytoseiidae), Mexecheles hawaiiensis (Baker)

(Pro stigmata: Cheyletidae), and Sticholotis punetata Crotch (Coleop-

tera: Coccinellidae).

P. macropilis was first reported from Hawaii in 1953 bv- - . .Cunliffe and Baker while this is the fir st report of A. largoensis for

74.

Hawaii. Besides Hawaii, the former species occurs in Florida,

California, Canary Islands, Puerto Rico, and Panama (Cunliffe and

Baker, 1953; and Chant, 1959), and the latter species in Florida,

Guatemala, Mexico, and Japan (Chant, 1959; and Ehara, 1959). Both

species of phytoseiids usually feed on spider mites, but when these

preferred sources of food become scarce, they feed on other mites.

Adults of P. m.acropilis and A. largoensis were seen on several

occasions feeding on eggs of B. phoenicis on the petioles, fruits, and

stems of papaya. After making contact with an egg, it took an adult of

P. macropilis two minutes to pierce the chorion and withdraw the

internal contents of the egg. Although P. macropilis and A. largo­

ensis feed on B. phoenicis eggs readily, there were no indications that

they are able to live and reproduce exclusively on them, for eggs and

larvae of these predators which occur commonly in association with

spider mite populations were never found within the colonie s of

B. phoenicis.

M. hawaiiensis was originally described from Hawaii based on

specimens collected in 1941 from papaya fruits at Kailua, Oahu

(Baker, 1949). Since then, this species has been collected on other

kinds of plants infested by B. :phoenicis from the islands of Maui,

Kauai, and Oahu. Also, this predatory mite has been reported from

Florida recently (DeLeon, 1962; and Muma, 1964). The larvae,

nymphs, and adults of M.hawaiiensis were seen feeding on all of the

75.

active stages of B. phoeniCis, and all stages of this predator were

found in close association with their prey. Individuals of M. hawaii­

ensis were seldom seen out in the open but were seen hiding in

crevices, beneath leaves, between fruits, and in other protected

places fr'om where they ambushed their prey. As a prey approached

one of these hiding places, the predator dashed out, grabbed hold of

one of the prey's appendages with its highly modified pedipalpi, and

carried the victim back to its hiding place for feeding. A venomous

substance was probably injected into the prey for it became paralyzed

simultaneous to being captured by.M.• hawaiiensis. The chelicerae

of the predator were inserted into one of the legs of the prey from

where in less than 10 minutes the body contents were completely with­

drawn, leaving only the exo skeleton unconSUn1ed. The remains were

carried and disposed outside the hiding place of the predator. The

few numbers of carcasses of B. phoeniCis left accumulating around

each hiding place suggest that M. hawaiiensis does not require much

food for sustenance. Out of a total of the 535 predators found in close

assoCiation with B. phoeniCis populations during 1962 and 1963, 467, or

87 per cent, of them, were M. hawaiiensis.

~ punetata, a tiny cocCinellid, was seen attacking~ phoenicis

for the first time in Hawaii in June, 1964. This predator was intro­

duced into Hawaii from China and Japan as early as 1894-95 to control

scales ~Fullaway, 1920). ~ punctata was not seen preying on

76.

B. phoenicis until this late date probably because of its nocturnal

feeding habit. Some 30 adults were seen feeding on B. phoenicis in­

festing papaya plants on the University of Hawaii Campus, Honolulu,

Hawaii, during four nights of observation. They appeared at dusk

from within the ground litter at the bases of the papaya plants and

climbed up the trunks to feed. When artifical light was directed on

them, they stopped feeding and moved away from the lighted area.

They finished feeding and left the plants before midnight. No indivi­

duals of §.. punctata were seen feeding on B. phoenicis during the day.

The population density of B. phoenicis on these papaya plants dropped

to a low level two weeks after §.. punctata adults were first seen in

close association with the mites. This sudden reduction of the B.

phoenicis population was undoubtedly caused by~ punctata for

dissections of some of the adults caught before returning into the

ground litter showed fragments of m.any individuals and all stages of

~ phoenicis in their digestive tracts.

Enzootics or epizootics caused by pathogenic organisms, such as

fungi, bacteria, and viruses, were not encountered in populations of

B .. phoenicis.. However, two species of fungi, Hirsutella besseyi

Fisher and H. thompsonii Fisher, were found infecting other species of

phytophagous mites ..

All of the above-mentioned predators have been observed to bring

under control isolated populations of~. phoenicia; however, they are

77.

inadequate as economic control agents because their predatory

activity became apparent only when the prey population density was

very high and severe plant damage had already been inflictedo There­

fore, in areas where economic control of B. phoenicia is needed,

other control agents must be introduced.

78.

Chemical Control

In recent years, many chemicals with acaricidal properties have

becom.e available but only a few of these can be used to control B.

phoenicis on papaya because of various limitations and restrictions.

Some of the pesticides which have been proven effective for the control

of the comm.on species of spider mites (Family: Tetranychidae) have

been shown to be ineffective against some species of false spider mites

(Family: Tenuipalpidae) (Pritchard, 1949; Hamilton, 1953; and

Morishita, 1954). Many more pesticides of the chlorinated hydrocarbon

than organophosphor'ous derivatives have been reported to give excellent

kill of false spider mites (Pritchard, 1949; Hamilton, 1953; and

Morishita, 1954). Some of the pesticides toxic to the false spider mites

cannot be used on certain kinds of plants because of their phytotoxic

propensity. Papaya, a cornmon host of B. phoenicis, was found to be

very susceptible to phytotoxic injuries when treated with most of the

organic pesticides which were used for the control of mites on other

crops prior to 1959 (Sherman and Tamashiro, 1959). Of the organo­

phosphorous pesticides, only Diazinon has been reported to give

excellent kill of a species of false spider mites, B. obovatus (Mori­

shita, 1954), but it was found to be extremely phytotoxic to papaya.

Malathion is innocuous to papaya but it proved to be ineffective against

B. phoenicis.

79.

Until recently, sulfur was the only pesticide known to be effec­

tive against B. phoenicis and also fairly safe to use on papaya from.

the standpoint of phytotoxicity under m.o st of the clim.atic conditions

which prevail in Hawaii. Since large am.ounts of sulfur, five to six

pounds of 95 per cent wettable powder, are required to give good con..

trol of som.e of the mites infesting papaya, m.any of the growers are

reluctant to apply this pesticide on fruit ...bearing plants because it

leaves unsightly deposits on the fruits. Furthermore, search for other

acaricides becam.e necessary because many species of m.ites coexist

on papaya and one of the most pestiferous of them, '!.. telarius, cannot

be controlled effectively with sulfur (Sherman and Tam.ashiro, 1959).

Those pesticides which have been reported to be fairly innocuous

to papaya (Sherman and Tam.ashiro, 1959), and those which gave negli..

gible injuries to fruit-bearing plants in preliminary studies, were

tested for their effectiveness against B. phoenicis. Of the pesticides

in which both wettable powder and emulsifiable formulations are known,

the former was selected because this form of most pesticides has been

shown to be less phytotoxic to papaya than the corresponding emulsi­

fiable form (Sherman and Tam.ashiro, 1959). The performance re sults

of the different pesticides used are shown in Tables VI, VII, and Vill.

Karathane, Diazinon, and aram.ite gave good control of B .. phoenicis on

other plants but were not used in this study for they were found to be

very phytotoxic to papaya.

80.

All concentrations of Kelthane, Pentac, and Morestan and

certain of the higher concentrations of Chlorobenzilate, sulfur, and

ovex gave good kill of !h. phoenicis adults (Table VI), but most of

thero showed poor ovicidal properties (Table Vill). Morestan was the

only pe sticide which caused high mortality of both the adult and egg

stages. Malathion, at all concentrations, caused no significant kill of

B. phoenicis females, but the lower concentrations of this pesticide

appeared to have induced oviposition in the treated feroales (Table VII).

B. phoenicis adults died within 2.4 hours after applying lethal

dosages of Kelthane and Chlorobenzilate, whereas those treated with

lethal dosages of Pentac, Morestan, ovex, and sulfur died four to

seven days after treatroent. Although the females Lived for several

days after treatroent with these pesticides, they fed very little, laid

only few eggs (Table Vil), and remained lethargic most of the tim.e.

Adults treated with Kelthane and Chlorobenzilate died with their legs

fully extended and their body posture posed like that of living indivi­

duals while feeding or when at rest so, until probed, the freshly killed

individuals were difficult to distinguish from the living ones. Those

killed by the other pesticides were readily distinguishable from the

Living ones for they died with their front two pairs of legs retracted

beneath the venter of the body.

Many of the eggs that were deposited on the surfaces of the rn.edia

just prior to and after expo sure to treatroent with all concentrations of

81.

Kelthane, Pentac, ovex, and sulfur, and with concentra.tions less than

one pound active material of Chlorobenzilate per 100 gallons of water,

hatched 10 to 12 days later and the resulting larvae fed and continued

to develop on the treated media without showing ill effects from the

residues. Apparently, these pesticides lost their toxic properties

within 10 days under laboratory conditions. If this is true, they un­

doubtedly deteriorate to non-toxic levels much faster under field con­

ditions. When using one of these pesticides with poor ovicidal and

seemingly short residual properties, a second application within two

to three weeks after the first becomes necessary in order to control

B. phoenicis effectively for it can escape control in the egg stage

which has a fairly long incubation period.

Although effective against B. phoenicis, some of the above­

mentioned pesticides and their concentrations should not be applied

to fruit-bearing papaya plants because of phytotoxicity. Oozing of

latex from the epidermis of green fruits in areas where large amounts

of pe sticide g had accumulated were noticed soon after applying ovex at

two pounds, Chlorobenzilate at one and two pounds, and Pentac at

two pounds of active material per 100 gallons of water under field

conditions. These areas of latex exudations developed into scars of

various sizes and shapes in about three weeks after the pestkide

application which greatly marred the appearance of the fruits

.Figure !8~ L1'ljury caus.ed by Ghlol"'obenzilate at 1 poundof active material per 100 gallons of water"

82•

Figure 19. Injury caused by Pentac at Z pounds activematerial per 100 gallong of water.

83.

Figure 20. Injury caused by ovex at 2 pounds activematerial per 100 ga.llons of wa.terg

84.

85.

(Figs. 18, 19, and 20). Kelthane and Morestan were found to be

innocuous to papaya fruits at concentrations as high as two pounds of

active material per 100 gallons of water, but they are not recom­

mended for use at these high dosages for not only is it uneconomical

but the unsightly depo sits on the frui~s mentioned earlier would be a

problem.

Kelthane, Morestan, Chlorobenzilate, Pentae, and ovex are not

to be used on papaya grown for the commercial market as they have

not yet been cleared for use on this crop. Sulfur and Volck Oil

Supreme are the only two pesticides which are toxic to some of the

stages of B. phoenicis and can be used on papaya for they are exempt

from the requirement of a tolerance. Whereas mo st petroleum oils

and even er.L.ulsifiable forms of many pesticides are known to be phyto­

toxic to papaya, Volck Oil Supreme, a highly refined petroleum oil,

caused no obvious phytotoxic injury to fruit-bearing papaya plants.

TABLE VI. PERFORMANCE OF DIFFERENT. PESTICIDES AGAINST THE ADULTS OFBREVIPALPUS PHOENICIS (GEIJSKES)

Pounds activematerial per

Pesticides 100 gallons Formulations No. Alive a/ Statistical significance b/

Malathion 1/4 25% WP 5.10Ovex 1/4 50% WP 5.05Check 5.02Malathion 1/2 250/0 WP 5.02Malathion 1 25% WP 4.90Malathion 2 25%WP 4.70Ovex 1/2 50% WP 4.48 --'I ]Chlorobenzilate 1/4 25%WP 3.92Volck Supreme 3 EC 3.25 :::JVolck Supreme 2 EC 2.55 J]Volck Supreme 6 EC 2.38Volck Supreme 4 EC 2.15Ovex 1 500/0WP 2.10Sulfur 3 95% WP 1. 90 ]Chlorobenzilate 1 25% WP 1.45

lSulfur 4 95% WP 1.40Pentac 1/4 50% WP 1.35Chlorobenzilate 1/2 25% WP 1.25

0:>0'•

TABLE VI. Con.tinued

Pesticides

MorestanMorestanMore stanMorestanChlorobenzilateOvexSulfurSulfurPentacPentacPentacKelthaneKelthaneKelthaneKelthane

Pounds activematerial per

100 gallons

1/41/2

122256

1/212

1/41/2

12

Formulations

250/0 WP25%WP25% WP25%WP25%WP50%WP95% WP95%WP50%WP50% WP50%WP25%WPZ5%WP25% WP25%WP

No. Alive eJ

1.201.101.001.001.001.001.001.001.001.001.001.001.001.001.00

Statistical Significance "'e.l

a/ N III 25. Average of four replications. The data were transformed according to the formula

.jXfT.b/ At 5 per cent level, according to multiple range test of Duncan (1955).

WP =. Wettable powderEC a Emulsifiable concentrate

00-.].

TABLE VII. NUMBER OF EGGS OF BREVIPALPUS PHOENICIS (GEIJSKES) COUNTED ONTREATED SURFACE ONE WEEK AFTER .APPLICATION OF THE DIFFERENTPESTICIDESo

PoUnds activematerial per

Pesticides 100 gallons Formulations No. of eggs a/ Statistical significance b /

Malathion 1/2 250/0 WP 194.75 ::JMalathion 1/4 250/0 WP 138.75Malathion 1 250/0 WP 129.75Check 128.50Ovex 1/2 500/0 WP 116.25Malathion 2 250/0 WP 110.75Ovex 1/4 500/0 WP 105.50Valek Supre:rne 3 EC 68.50 =:1Chlorobenzilate 1/4 250/0 WP 32.50Volck Supreme 6 EC 20.75Ovex 1 500/0 WP 20.50Volek Supreme 2 EC 19.25Sulfur 3 950/0 WP 19.25Pentac 1/4 500/0 WP 16.50Pentac 1/2 500/0 WP 16.25Ovex Z 500/0 WP 13.75Sulfur 4 950/0 WP 13.50Sulfur 5 950/0 WP 12.75

0:>0:>•

TABLE VII., Continued

Pesticides

Pounds activematerial per100 gallons Formulations No. of eggs al Statistical significance bl

Volck SupremeMore stan

SulfurPentacKelthanePentacMorestanMorestanMorestanKelthaneKelthaneChlorobenzilateChlorobenzilateChlorobenzilateKelthane

41/4

61

1/2212

1/21

1/41/2

122

EC25%WP95% WP50%WP25%WP500/0 WP250;0 WP25%WP25%WP25%WP25%WP25%WP250;0 WP25%WP25% WP

11.7511.2510.7510.7510.5010.009.759.508.507.757.507.507.507.506.50

;;j Average of four replications. Pre-treatment N = 25 females.Eggs laid prior to death or during first week afj;er treatment.

r:J At 5 per cent level, according to multiple rang~: test of Duncan (1955).

WP =EC =

Wettable powderEmulsifiable concentrate

00--D.

1'ABLE Vill.. OVICIDAL EFFECT OF DIFFERENT PESTICIDES ON THE EGGS OFBREVIPALPUS PHOENICIS (GEIJSKES).

Pounds activematerial per Per cent of

Pesticides 100 gallons Formulations eggs hatched al Statistical. significance b/

Check 87.0 ]Malathion 2 25% WP 84.0Sulfur 6 95% WP 80.5Keltha.ne 2 25% WP 69.5 ]Ovex 2 50% WP 68.0Pentac 2 50%WP 67.5Chlorobenzilate 2 25% WP 55.5 :::JVolck Supreme 6 EC 14.0 ::JMorestan 1/4 25% WP 2.5 ]Morestan 2 25% WP 1.5

a/ Average of eight replications. N· 25 eggs per replication..

bl At 5 per cent level, according to multiple range test of Duncan (1955).

WP = Wettable powder formulationEC ~ Emulsifiable concentrate

-.0o.

91.

DISCUSSION

Studies on the biology of B. phoenicis have revealed that this

species has many attributes in common with the other well-known

false spider mites, 1b obovatus andlh californicus. Like them, B.

phoenicis is polyphagous, reproduces mainly by parthenogenesis,

males are very scarce, life cycle is fairly long, and it is tolerant of._-,-- .

certain of the organophosphorous pesticides. Despite these similari-

ties, B. phoenicis possesses certain attributes which seem to be dis-

tinctive for the species. The most striking attribute is its ability to

thrive only within fairly narrow temperature range, while B. obovatus

and !h californicus reproduce freely within a wider temperature

range, 20°C and 30o C, with very little mortality occurring during the

developmental stadia under laboratory conditions (Manglitz and Cory,

1953; and Morishita, 1954). The distributional patterns of these false

spider mites in nature are in line with the laboratory findings. Here

in Hawaii, B. phoenicis is very abundant only along the coastal areas

to about 1,000 feet elevation where the temperature is fairly uniform

throughout the year and does not deviate too greatly from 2.50 C for any

length of tim.e, whereas the other two false spider mites are more

widely distributed from sea level to about 3,500 feet elevation where

the ten'lperature conditions at the higher elevations are m.ore variable

and often drops below 2.0oC for extended durations (Ripperton and

Hosaka, 1942.). Also, both B. obovatus and B. californicus have been

92,

reported from more countries outside the tropics tha,n B. phoenicis

(Pritchard and Baker, 1958).

Another distinguishing attribute of B. phoenicis is its feeding

preference on the stems of plants. The foci of B. phoenicis infesta-

tions are usually located on the stems while those of B. obovatus and

~. californicus are invariably located on the lower surfaces of leaves.

These mites move away from their preferred feeding sites to other

parts of the plant only when overcrowded conditions prevail.

Although the life cycles of the three false spider mites were,

carried out under slightly different laboratory conditions by the vari-

ous workers (Manglitz and Cory, 1953; and Morishita, 1954), all

indications are that the life cycle of B. phoenicis is definitely longer

than those of B. obovatus and B. californicus. B. phoenicis com-

pleted its development from the egg to the adult stage in 18.6 f:. 0.5

days at 30oC, 29.3 I:. 0.4 days at 250 C, and 48.9 /:. 1.5 days at 20o C.

At the sam.e respective temperatures, the average developmental

periods of B. obovatus were reported as 16.4, 28.0, and 42.0 days

by Morishita (1954)0 Dosse (1959) found that B. phoenicis required

about two days longer than~ obovatus to complete its development

on ivy leaves at 24oC. Of the three species of false spider mites,

B. californicus seems to have the shortest life cycle for }/ianglitz and

Cory (1953) were able to rear this mite from egg to the adult stage

in 26.2 days under temperature conditions ranging between 17. 90C

and 23. 9°C. Whereas the developmental rate of false spider mites

is much faster at temperatures above 250 C than below it, the life

cycle of B. califomicus is two to three days shorter at temperatures

below 250 C than those of B. obovatus and B. phoenicis at 250 C.

The developm.ental rate of the above three specie s of false

spider mites is slow in comparison to that of som.e of the spider

m.ites. Tetranychus desertorurn Banks and T. telarius (L.) are

known to develop from. eggs to adults in just 6.90 t. 0 .. 5 days and

7.09 t 0.17 days, respectively, at 300 C (Nickel, 1960), while the

false spider mites, B. phoenicis and B. obovatus, require on an

average of at least 18.6 and 16.4 days, respectively, at the same

temperature conditions. The conditions under which developm.ent is

m.ost rapid is not necessarily favorable for population increase since

m.ortality during the im.m.ature stage s can be much greater than

natality as was shown in this study. Therefore, when optimum. survi­

val conditions are taken into consideration, the developmental period

of B. phoenicis is about four times longer than those figures shown

above for the spider m.ite s.

The fecundity of both ~ phoenicis and B. obovatus is less than

that of som.e spider mites. Tetranychus atlanticus McGregor, T.

telarius, and T. desertorum females are capable of laying as many

as 230, 194, and 187 eggs per individual, respectively (Cagle, 1949

and 1956; and Nickel, 1960); however, the maximum laid by any

94..

species of false spider mite female is only 76 eggs. This low

fecundity and the long developmental period of the false spider mite s

are probably the main reasons why they are only occasional pests of

perennial plants and are not as serious pests of agricultural crops as

the spider mites. In Ceylon, B. phoe~ is reported to require

about three year s to reach economi c proportions on tea plants which

are pruned (Baptist and Ranaweera, 1955). Here in Hawaii, B.

phoenicis normally requires about a year to build up to densitie s high

. enough to cause noticeable damage to papaya.

Since B. phoenicis reproduces mainly by parthenogenesis, it

seems reaso:n.able to assume that the genetic composition of a popu-

lation of this mite within an area is fairly uniform. Resistance to

pesticides is less likely to be selected out from such a population

because the gene pool is more limited than that of sexually reproduc­

ing species as the spider mites. This is probably the mai.Tt reason

why resistance to acaricides which were once proven effective has

not been reported for the false spider mites, whereas resistance to

pesticides is a notorious and serious problem in the case of spider

mites (Jeppson, 1961)0 However, the frequency of application of

selection pressure such as a pesticide should be taken into consider­

ation. Since the false spider mites are only occasional pests of

agricultural crops, none of the acaricides have been used extensive­

ly for their control as for spider mites and this also may be a reason

95.

why resistant populations have not yet been selected out.

Although. chemical control is the most effective means of sup­

pressing outbreaks of B. phoenicis, :many problems can arise in the

atte:mpts to control this mite with che:micals. When chernical control

is needed on a food crop, one :must rnake certain that the pesticide

selected for application is approved and recom.:mended for usage on

the particular crop and is used in strict accordance with the directions

stipulated on the labels of the pesticide containers. On certain crops,

only a few pesticides are cleared for use and these registered pesti­

cides may not be toxic to B. phoenicis even though they have been

shown to be effective against other closely related species or they may

be toxic to only certain stages of B. phoenicis. Here in Hawaii, when

using pesticides which kill only certain stages of the mite, several

applications within relatively short intervals are necessary for all

stages of~ phoenicia are present simultaneously the year around

and the duration of certain of the stages is longer than the residual life

of rnost pesticides. Cornbinations of pesticides, one that kills the egg

with another that kills the active stages, seem like a ready solution

to the problem of necessity of several and/or separate applications,

but other problerns can arise in doing so. Sorne pesticides are

innocuous to plants and very effective against certain stages of B.

phoenicis when applied singly, but when co:mbined they :may becorne

either phytotoxic due to synergism or rnay become ineffective against

96.

the rnites. Furthennore, not all pesticides are cornpatible with each

other.

Some pesticides are very effective against B. phoenicis but they

cannot be used because certain of the host plants of this mite are very

susceptible to chemical injury. The reader is referred to the papers

by Gast and Early P956) and Sherman and Tamashiro (.1959), and to

the textbooks by Bailey and Smith (1951), Brown (1951), and Shepard

(1951) for concepts on the phytotoxic properties of pesticides..

97.

SUMMARY

The red and black flat mite, Brevipalpus phoenicis (Geij skes),

is widely distributed throughout the tropical areas of the world. In

Hawaii, this mite is very abundant on all of the major islands along

the coastal areas up to about 1,000 feet elevation. The climatic

conditions in these areas are favorable for continuous reproduction

of B. phoenicis throughout the year.

B. phoenicis inhabits and feeds on approximately 100 different

kinds of plants. It is a major pest of perennial plants such as papaya,

pas-sion fruit, tea, citrus, and several species of ornamentals. It

usually feeds on the sterns of plants, but when food and space become

limiting due to overcrowded conditions, some individuals move to

other parts of the plant and form. colonies.

Morphologically, B. phoenicis is a variable species. For this

reason, several synonyms have been created. The most variable

structures are the dorsolateral hysterosomal setae I and II, and the

dor socentral hystero somal setae III of the larvae and nymphs. The Be

vary from a tiny~ serrate setae to a large, broadly lanceolate,

serrate setae. The larva, protonyrnph, and deutonyrnph of B o

phoenicis are ve:r:-y similar to those of ~o obovatus Donnadieu» but the

adults are readily distinguished from the latter specieso B o phoenicis

is the only species known to have two pairs of sensory rods on tarsus

II and five pairs of dorsolateral hysterosomal setae in the adult stage.

98.

The life cycle of B. phoenicis is greatly influenced by tempera­

ture and hum.icIity conditions. The larva, protonymph, and deuto­

nymph spend about one-half of their stadia as active individuals and

the remainder of the time as inactive individuals. Feeding, growth,

and limited dispersion are accomplished during the active phase and

ecdysis occurs during the inactive phase. The average durations of

the different stages range from. 8.2 1:. 0.4 days at 300 e to 22.6 I:. 1.1

days at 200 e in the egg stage, 3.6 1:. 0.2 days at 30°C to 10.5 t. 0.7

days at 200 e in the larval stage, 3.1 I:. 0.4 days at 300 e to 8.2 t 0.7

days at 200 e in the protonymphal stage, and 3.7 t 0.5 days at 300 e

to 7.5 f:. 0.9 days at 200 e in the deutonymphal stage. At 250 e and 65

to 70 per cent relative humidity, conditions most favorable for survi­

val and population increase, B. phoenicis completes development

from the egg to the adult stage in 29.3 f:. 0.4 days. Development is

much faster at temperatures above 250 e than below it; however,

mortality of the im.m.ature stages increases with deviation of tempera­

ture away from 250 e until completion of the life cycle is no longer

possible at temperatures above 300 e and below 20oe. All stages of

the mite are able to withstand brief exposures to temperatures below

200 e better than temperatures above 30oe.

The B. phoenicis adult population is predominantly female.

Males have been reported as non-existent in many parts of the world,

but here in Hawaii they make up about 1 per cent of the adult population.

99.

Since umnated females are able to give rise to exclusively female

progenies and males are very scarce, reproduction of the species

is mainly by parthenogenesis.

At 250 C and 65 to 70 per cent relative humidity, B. phoenicis

females start to oviposit in 3.5 1:. 0.9 days after emergence and lay

from one to four eggs per day for a total of 57.5 1:. 7.4 eggs per

female during their life span of 34.8 1:. 4.5 days. Preoviposition

period is longer at 300 C than at 250 C or 20o C. Females live longer

but lay only one-fifth as many eggs at 200 C than at 250 C.

Four species of predators; Phytoseiulus macropilis (Banks),

Amblyseius largoensis (Muma), Mexecheles hawaiiensis (.Baker), and

Sticholotis punctata Crotch, feed on certain stages of B. phoenicis in

Hawaii. Of these, M. hawaiiensis is the predominant predator. All

of the active stages of this cheyletid mite feed on the active stages of

B. phoenicis. These natural enemies control isolated populations of

~ phoenicis, but are often inadequate as economic control agents.

Chemical control measures can be used to effectively depress

outbreaks of B. phoenicis. Morestan is toxic to all stages of the

mite, whereas Chlorobenzilate, Pentac, Kelthane, and sulfur give

excellent kill of the active stages only. Volck Supreme, a highly re­

fined petroleum oil, gives good kill of the eggs of B. phoenicis but

only poor to fair kill of the adults. These pesticides are relatively

non-phytotoxic to papaya, a plant that is very susceptible to chemical

100.

injury, at the m.inim.um dosage of effectiveness to B. phoenicia.

Sulfur and Volck Oil Supreme are the only two pesticides which can

be used to control &. phoenicis on papaya grown for the com.m.ercial

m.arket, while the other above-m.entioned pesticides are not yet

registered for use on this crop. All stages of B. phoenicis are

tolerant of m.alathion, an organophosphorous pesticide which is

approved for usage on papaya and claimed to kill certain species of

spider m.ites.

101.

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