REDUCED FECUNDITY OF RHYZOPERTHA-DOMINICA (F) (COLEOPTERA, BOSTRYCHIDAE) FOLLOWING EXPOSURE OF ADULTS TO METHOPRENE

Experiments were carried out to determine whether exposure of Rhyzoper tha dominica (F.) adults to wheat treated with methoprene affected the ir fecundity when subsequently transferred to untreated wheat. The juv enile hormone analogue methoprene is effective in controlling progeny of this species without killing parents. Therefore, there is the poten tial for adults to fly from treated grain and oviposit in untreated gr ain. Adult R. dominica were confined for 1-8 days to wheat that had be en treated with methoprene at 0.01-4 mg kg(-1). After exposure the adu lts were transferred to untreated wheat for 7 days, and in some cases there was a second similar transfer. Exposure to methoprene for as lit tle as 1 day resulted in reduced fecundity in the first week following exposure, and this reduction was related to dose. Fecundity was reduc ed by about a half following exposure to a dose of 2 mg kg(-1). Fecund ity in the second week following exposure was not affected. The study shows that, as with some other insect growth regulators, there is a te mporary reduction in fecundity of R. dominica adults after exposure to methoprene, Thus although methoprene can be expected to protect grain , parental insects flying from treated grain will be capable of infest ing untreated grain or residues. (C) 1998 Elsevier Science Ltd. All ri ghts reserved.