[Please note, this is a test version only. You may visit the current Orchard Pest Management pages at http://jenny.tfrec.wsu.edu/opm]
Phenacoccus aceris Signoret
-- Elizabeth H. Beers
(Published online December 2007)
Apple mealybug on woolly apple aphid root gall (E. Beers, April 2006)
Despite the common name of “apple” mealybug, this insect is by no means a specialist. The host range is very broad, including all deciduous fruit and nut trees (apple, cherry, pear, plum, apricot, filbert), small fruits (grape, currant, gooseberry, blueberry) many shade trees (maple, oak, birch, willow, ash, linden, elm, mountain ash) and various ornamentals (cotoneaster, hawthorn, quince, spirea). The alternative common name, the polyphagous tree mealybug, is more indicative of this broad host range.
Apple mealybug eggs (closeup) (E. Beers, June 2007)
Apple mealybug nymphs by leaf midvein (E. Beers, June 2007)
Apple mealybug females and nests on apple twigs (E. Beers, May 2007)
Life HistoryAll reports in the literature specify one generation per year. The information from the Pacific Northwest is scarce, thus much of the information is taken from other areas. The apple mealybug overwinters as a second instar nymph in a cocoon under bark scales or in cracks in the bark. Feeding is done by inserting the proboscis into plant tissues (bark or leaves) and sucking plant sap. They emerge from overwintering sites very early in the spring, feed on twigs, mature to the adult stage (male and female) and mate. Egglaying begins in early May in central Washington.
Apple mealybug nest (closed) (E. Beers, May 2007)
(E. Beers, August 2007)
MonitoringThere are no formal schemes for monitoring apple mealybug. When they are abundant, the egg sacs are quite apparent, and will give an indication if later control is required. In some cases, only a few areas in an orchard may have sufficiently heavy populations to merit control.
Apple mealybug mummy (parasitized); with ovisac removed (upper)and with ovisac intact (lower). Note the adult parasitoid's exit holes in the ovisac. (E. Beers, July 2007)
Information on the natural enemy complex in Washington is scarce. A parasitic wasp (probably an Anagyrus sp) was found attacking a heavy infestation of apple mealybug in an organic orchard. A high percentage of the overwintering generation was parasitized. Interestingly, the female mealybug could lay viable eggs despite being the host for one or more adult parasitoids. The females and males of this parasitoid species have very different appearances, and may be mistaken for separate species. Adult parasitoid emergence occurred about the same time as egg hatch of the mealybugs.
ManagementControl recommendations in Washington are speculative at this point. The recommendations on cherry, in an area where the virus is known to occur, should be more stringent. British Columbia recommends controls at dormant, petal fall, summer and post harvest. Control recommendations in other crops can be more in line with population density. Dormant or delayed dormant sprays should reduce the population if they have emerged from their overwintering sites. The period of crawler emergence in early to mid-June is likely another vulnerable point in the life cycle, although no control studies on apple in this region have been done. Conventional insecticides and insect growth regulators used against grape mealybug are likely effective. In organic orchards, neem insecticides, timed for crawler emergence, appear to provide some control. Spray practices (e.g., high gallonage) that cover the undersides of the leaves and crevices in the bark will likely be more effective. Once they begin feeding, mealybugs are not very mobile, and they will not move around to contact a sparsely applied spray. Avoiding pesticides that destroy parasitoids should also help keep this species at a low level.
British Columbia Ministry of Agriculture and Lands. Apple mealybug, Phenacoccus aceris (Signoret).
British Columbia Ministry of Agriculture and Lands. British Columbia Ministry of Agriculture and Lands. 2007. Little cherry disease in British Columbia.
Chachoria, H. S. 1967. Mortality in apple mealybug, Phenacoccus aceris (Homoptera: Coccidae), populations in Nova Scotia. The Canadian Entomologist 99: 728-730.
Eastwell, K. C., and M. G. Bernardy. 2001. Partial characterization of a closterovirus associated with apple mealybug-transmitted littel cherry diseas in North America. Phytopathology 91: 268-273.
Gilliatt, F. C. 1935. A mealy bug, Phenacoccus aceris Signoret, a new apple pest in Nova Scotia. The Canadian Entomologist 67: 161-164.
Gilliatt, F. C. 1936. Observations on the mealy bug, Phenacoccus aceris Sig. The Canadian Entomologist 68: 133.
Gilliatt, F. C. 1939. The life history of Allotropa utlilis Mues., a Hymentoperous parasite of the orchard mealy bug in Nova Scotia. The Canadian Entomologist 71: 160-161.
Kozar, F., L. M. Humble, R. G. Foottit, and I. S. Orvos. 1989. New and little known scale insect (Homoptera: Coccoidea) from British Columbia. Journal of the Entomological Society of British Columbia 86: 70-77.
Madsen, H. F., and P. J. Proctor. 1982. Insects and mites of tree fruits in British Columbia, pp. 1-70. Ministry of Agriculture and Food, Victoria, B.C.
Marshall, J., and A. D. Pickett. 1944. The present status of the apple mealybug, Phenacoccus aceris Sig., in British Columbia and Nova Scotia [Note]. The Canadian Entomologist 76: 19.
Marshall, J. 1953. A decade of pest control in British Columbia. Proceedings of the Entomological Society of British Columbia 49: 7-11.
Muesbeck, C. F. W. 1939. A new mealybug parasite (Hymenoptera: Scelionidae). The Canadian Entomologist 71: 158-160.
Raine, J., R. D. McMullen, and A. R. Forbes. 1986. Transmission of the agent causing little cherry disease by the apple mealybug Phenacoccus aceris and the dodder Cuscuta lupuliformis. Canadian Journal of Plant Pathology 8: 6-11.
Turnbull, A. L., and D. A. Chant. 1961. The practice and theory of biological control of insects in Canada. Canadian Journal of Zoology 39: 697-753.