Susceptibility of seven tetranychids to the nonoccluded virus of the citrus red mite and the correlation of the carmine spider mite as a vector

JOcRXaL

OF INVERTEBR.yD:

Susceptibility of the Citrus

20, 279-283

PATHOLOGY

(1%)

of Seven Tetranychids Red Mite and the Spider

Mite

J. B. BEAVER+ Entomology

Research USDA

Divkion, Riverside, Received

to the Correlation

Nonoccluded Virus of the Carmine

as a Vector AND D. K. REED Agrkultural C&I~ornkz May

Reseawh 325OZ

Service,

9,13’78

When the European red mite, PanoTlychus dni; the avocado brown mite, Oligonychus puuicae; the twospotted spider mite, Tekrarzychus urkae; the carmine spider mite. 2’. cinnabarims; the Pacific spider mite, T. pac$cm; the sixspotted mite, Eotetranychus sexmuculatus; and T. evansi were exposed to the nonoccluded virus of the citrus red mite, Panonychus citri, either by feeding on contaminated citrus leaves or by spraying with aqueous suspensions of t,r&urated diseased mites, only a few carmine spider mites developed the crystals characteristic of the disease. However, the carmine spider mite was a vector of the virus: when citrus red mit.es were transferred to leaf cages previously inhabited bJ carmine mites from contaminated cages, they became diseased; also, aqueous suspensions of triturated carmine mites t,hat had been sprayed with virus inoculum from citrus red mites passed the disease to citrus red mites.

citrus red mite and the European red mite, t8herefore, appeared similar. Also, Ignoffo (1968) has reported that nonoccluded viruses are the least host specific of the insect viruses. Studies were therefore undertaken at the Arid Areas Citrus Insects Investigations Laboratory at Riverside, California, to determine whether the citrus red mite virus would infect other species of tetranychids and, if so, whether these species might be a factor in perpetuating the virus in the field during periods of low populations of citrus red mites.

Since the discovery of a nonoccluded virus disease of the citrus red mite, Pano~.~C/LUS&ri, in 1958 (Munger et al., 1959; Smith et al., 1959), Gilmore (1965) has reported the initiation of a field epizootic with suspensions of diseased mites, and Tashiro and Beavers (1966) have reported a naturally occurring epizootic. Also, the occurrence of this disease in citrus red mites in most citrus growing areas of central and southern California has been reported (Shaw et al., 1968). In addition, Steinhaus (1959) has reported a possible virus disease of the European red mite, P. W&Z& collected from English walnut near San .Jose, California. Putman and Herne (1966) have reported similar symptoms in the European red mite in a peach orchard in Ontario, Canada, and Putman (1970), lat’er, confirmed that these symptoms were caused by a nonoccluded virus. The etiology of the diseases affecting the 1 Present

address:

Orlando.

Florida

METHODS

The species tested were the citrus red mite; the European red mite; the avocado brown mite, Oligonychus punicae; the twospotted spider mite, Tetyanychus urticae; the carmine spider mite, T. cinmbarinus; the Pacific spider mite, T. pacificus ; the sixspot,ted mite, Eotetranychus sexmacula~/Ls; and T. ez~~~~.si. The adult female citrus 14 mites (CRM’\ were obtained from the

32803.

279 Copyright Ml rights

6 1973 by Academic Press, Inc. of&eproduction in any form reserved.

AND PROCEDURES

230

BEAVERS

latioratory colony where they were maintained as described by Munger (1957). The mites of the other species were either ohtained from laboratory colonies maintained at the Vniversity of California or collected in the field in California. All mite&< were always transferred from test cage t’o test cage with artist’s (000) hrushrsZ and all tests were made at, a temperature of ?a. 27OC and .50-6074, RH. Virus infection wa.s determined by removing mitcs from the test cages, mounting them in Hoycr’s medium, and examining them microscopically under polarized light for the presence or absence of the characteristic birefringcnt crystals. These crystals are present in pa. 8.5~4 of laboratory-infected CRN I Smith anal Cressman, 1962) and have bun used consistent,ly for diagnosis since they are the only detectal& manifestation of disease in individual mites (Tashiro ct al.. 1970). The virus affecting the European red mite (,Putman, 1970’) was not availahlc to us for reciprocal testing against the CR&l (IV. 1,. Putman. pen+..comm.) TESTS

Suxeptibility C?RM T-irus

.~ND

REWLTS

o,f Tekmychid

Species

to

For the vector feeding tests. the surfaces of lemons inside cages (Munger, 1957’) were contaminated with virus by introducing diseased adult CRM into each cage and allowing them to feed until most were dead. Similarly, healthy CRM were introduced into control cages. Then, 24 hr after these vector mit,es were removed, healthy specimens of the test species were placed in the cages. For the spray tests, cages were first stocked with the test species. and then, 1 ml of triturated suspension of 1 mg diseased mites per milliliter distilled water was atomized into each cage (1 ml of distilled water tias atomized on the control mites). With each species, 8 replicates of 10 mit.es each were treated by both methods

AND

REED

and 4 replicates of 10 mites each served ah controls. However, the vector feeding tests with the European red mitt were replicatc~~l 16 timt~s and with the carminr spider mitcx :r total of 24 times in 3 stparatc t&s. Also, iii the spray tests with T. euansi, tomato leaves wcr(s WNI instead of lemon, ancl with avocado brown mites, avocado leaves w(sr(s used. Drawl mites wtre rcmovcd periodically after the cxliosure~ and ~xamiiied for x.irus. Inoculatcld CRN were used as a control bioassay for virus infectivity. 0f the 7 species of tctranychids testecl. only t’he carmine spider mite in the vector feeding test manifested hirefringent crystals (6.2% infcctcd) similar to those present iii infcctecl CRM (51.8c: infected). No evidence of that (liagnostir crystals was foun~l in any sprayed mites though CRM infected hy this method had .52.q5c( infection. Also. no infection occurrecl in the untreated controls in either test Two additional amI Gmilar trials wcrt ma&~ with carmine spider mites (disca~c~l CR11 adults used a~ vectors). A mean of 12.3$ of the exposed carmine mites had the characteristic hirefringent crystals compared with a mean of 48.3% of the CRM. Keither the carniiii~~ spider mite nor th(b CR&l controls were infclcte(l. (‘amine Spider CR&f Virus

Mite

Te*sted as T’ector

of

In t’he first t’est of the carmine spider mitt1 as a vector of CRM virus, infectious CRN were introduced into a first set of 40 acrylic ktaf cages (Tashiro, 1967 J that, were held on port,ahle watering platforms (Beavers and oldfield, 1970) for 4 days; also, healthy CRhI were introduced into 12 similar (cont’rol) cages and held for 4 days. Then, all mites were removed, and 5 from each cage’ were examined for virus infection. Twentyfour hours later, 20 of the contaminated cages were stocked with healthy CRM and 20 with healthy carmine spider mites. Also, 6 of the control cages were stocked with

CITRUS

RED

MITE

VIRUS

IN

281

TETRANYCHIDS

h(lalthy CR11 and 6 with healthy carmine qjider mites. After all mites fed for 3 clays, they where transferred to a second set of fresh cages and allowed to feed 4 days befort> th(y were removed and examined. Twenty-four hours later, the second set of cage+ was stock1 kth healthy CRM and loft for 7 days; then t’liese mites too were reino~~(l and ~~xaininr(l.

Gilmorc and Tashiro (1966) demonstrated that CR11 infected with virus could transmit the diseabe within 24-48 hr, and Ta~hiro et al. ( 1970 1 showed that the virus 011 (,oiita~~lili:~t~l(l lemons hold in Munger (*ages l)crsisted for as much as 28 days. A t(xst 1~:~sniadc to (l&ermine the infectivity to C’RAI of various ljcriods of feeding by (‘RN and by the carmine spiclcr mite. In tb(> fir>t trial, diseasecl CRM and exposed carmin(~ q)i(lcr mitts (presumed to be inf(b(Qd) were place(l in clean leaf cages and l(*ft foi. 4 (lays; then tlicy wcxrr removed, and thcb cages were stocked with healthy (-‘RJJ, In t#lie secon(l trial, similar mites w(lrc IJIaced in one set of clean cages whcrc they remained for 4 days; after they wcx? r~move(l from each set of cages, t’he cages w(lrc stocked with healthy CRM. In the third trial! Gmilar initcxs were removed from ~:tg~ after 24 hr, but th(> cages were not .~tocl<(~~lwith healthy CRM until 7 days later. Y%v rc>sults are shown in Table 2. 111 t,he s~ond test of the carmine spider ~~~it~~ w a v&or of CRM virus, carmine spider mitts collected in the field were brought into the laboratory and cultured on grc’en lemons, The population was sprayed

Vertor

species

Control

CRM

~

Test

CRM

‘6 A4fter -l days of feeding by the vector species. b L4ft,er 24 hr of feeding by the vector species inoculated in first set of cages and 4 days of feeding in the second set of cages before introduct,ion of healthy CRM into the second set of cages. r -4fter 24 hr of feeding by the vector species and a 7.day interval without mites hefore the introdllction of healthy CRM.

282

BEAVERS

once or t,wice a week for 5 weeks with a triturated suspension of diseased CRM (1 mg diseased mites/ml clistilled water 1. Random samples of dcacl mites showed that a low percentage contained the characteristic cryst,als, but the population as a whole was apparently healthy and flourished. Two weeks aft’er the last application of spray, the mites were collected and stored in a desiccator ,iar at -27’C. Subsequently, 20 mg of these mites were sonicated in 20 ml of distilled water and atomized onto 18 lemons infestecl with healthy CRM deutonymphs. After 12 days, 34% of the CR&I \Tere infected; none of the unsprayed controls were infect’ecl. Thus, the carmine spider mite, though it, shows little indication of disease, is a source of virus inoculum infective to the CRM. The infectivity could hardly have resulted from sprays applied earlier since the aqueous suspensions are known to bc incffcctivc after a few hours (Gilmore and Munger, 1963).

Tashiro et al. (19701 suggested that the CRM virus might be perpetuated when field populations of the mite were low because of contaminated fruit or intact dead mites adhering to the foliage. Also, Tashiro and Beavers (unpublished) infected healthy CRiU by allowing them to feed through a parafihn membrane on lemons contaminatecl by infected CRM, but did not infect CRM that feel on lemons after infective mites had feel on the same area through the membrane. However, Orlob (1968) reported that 9 plant viruses were not transmitted by the feecling of T, urticae i = T. telarius) , but the excretions of t,he mites were infectious; since the mites acquired tomato mosaic virus in 10 set (after 16 hr of feeding, nearly 100% had acquired it’1 and since they transmitted tomato mosaic virus ancl potato virus X deposited on leaf surfaces, he suggested that feeding punctures could serve as infectible sites.

mD

REED

Our results indicate that the carmine spider mite acts as a vector of the CRM virus though its susceptibility to the disease remains questionable : in a preliminary examination with the electron microscope, no virus particles were found in the mid or hindgut of three carmine mites, areas where they arc known to occur in diseased CRM (Reed and Hall, 19721. Therefore, the sixspotted mite, the twospotted spider mite, and the Pacific spider mite, though minor pests of citrus in California (Ebeling, 19591, and also other insects that feed on citrus, may bc vectors of CRM virus picked up as a result of feeding at virus-infected sites or by fecal contamination of the mouth parts; then their subsequent feecling punctures and fecal deposits might serve as sites of virus infection for the CRM. ACKNOWLEDGMENT Appreciation is expressed to the following members of the Department of Entomology, Universit) of California, for supplying mites: M. M. Barnes for the European red mites; G. T. Striven for lhr sixpotted mite. the a\-ocado brown mite. the carmine spider mite, and T. WWLS~; and M. J. Jesser for the Pacific spider rnitcx. REFERENCES J. B., .~ND OLDFIELD, G. N. 1970. Portable platforms for watering leaves in acrylic cages containing small leaf-feeding arthropods. J. Econ. Entomo/., 63,3X%313. EBELIXG, IV. 1959. Citrus Pests in the United States, p. 224. I?L “Subtropical Fruit Pesk” Univ. Calif. Press, Berke1e.v. California. GILMORE, J. E. 1965. Preliminary field evaluation of a noninclusion virus for control of the citrus red mitr. J. Ecotz. Enfomo/., 58, 1136-1140. GILMORE, J. E., .~ND MIXGKR. F. 1963. Stability and transmissibility of a virus like pathogen of the citrus red mite. J. Znverfebr. Z’ufhol., 5, 141-151. GILMORE, J. E., .~XD T.~sHIR~. H. 1966. Fecundity, longevit,y, and transinfectivity of citrus reel mites CPunonychxs &fri) infected with a noninclusion virus. J. ZnveTtebr. PuthoZ., 8, 334339. IGSOFFO, C. M. 1968. Specificity of insect viruses. Bull. Entomol. h’oc. Amer., 14,265-276. MUWXR, F. 1957. Equipment and techniques BEAVERS,

CITRT.5

RED

MITE

VIRUS

in laboratory studies of t,he citrus red U.S. Dep. Agr. ARS SS-S9,5 pp. MLYXER, F., GILMORE, J. E.. .~ND DAVIS, W. S. 1959. A disease of citrus red mites. C’elij. c’ifrog., 44, 190,216. ORLOB. G. B. 1968. Relationships between Y’e~~NI>~UC~U.S w&rze Koch and some plant viruses. Viro/ogg, 35, 121-133. P~-T>I.~N, 14’. L. 1970. Occurrence and transmission of a virus disease of the European red mile, knof~&~.s &ni Koch. Cm. E~tornol.,

IX

virus

used mite.

102,30~321.

,%utomo~.,98, 808-820. D.

K..

microscopy infecting Pathol.,

SII.JIV,

in

central

Econ.E~~~omoL,61,

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and

southern

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j.

1492-1495.

K. M., AND CRESSMAN, A. W. 1962. Birefringent crystals in virus-diseased citrus red mites. J. Insect P&ho/., 4, 229-236. ,SNTH, K. M., HILLS, G. J., MUKGER, F., AND GILhiORE, J. E, 1959. -4 suspected virus disease of the citrus red mite. Punonuc/w cilri (McG.). Kuture (London). 184, 70. STEINHAUS, E. A. 1959. Possible virus disease in European red mite. J. Znsect Puthol., 4, 435SNTH,

437.

W. L.. ASD HERA-E. D. H. C. 1966. The role of predators and other biotic agents in regmating the population density of phytophagus mites in Ontario peach orchards. Cr~r.

PI-~31.4~.

Rwn,

TETRANYCHIDS

.~XD

of the in press.

HALL. I. M. 1972. Eleckon rod shaped noninclusion virus ritrus red mite. J. InLlerfebr.

J. G.. T.~SHIRO, 1968. Infection of

H,,

ASD

the

citrus

DIETRICK,

red

mite

E,

with

J,

T.~SHIRO,

for

H. 1967. Self-watering confining insects and mites

acrylic cages on detached

~eaves.J.Eco?t.Ento?d.,60,354-356. H., AKD BEAVERS, J. B. 1966. Field epizootic of the citrus red mite virus disease. culij. citrogr., 51, 503-506. T.4sHIR0, H., BEAVERS, J. B., GROZA. M., AND MOFFITT, C. 1970. Persistence of a nonoccluded virus of the citrus red mite on lemons and in intact dead mites. Y. Int,edebr. Pathol,, 16, TASHIRO,

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