SEXUAL DIFFERENCES IN INSECTICIDE SUSCEPTIBILITY AND SYNERGISM WITH PIPERONYL BUTOXIDE IN THE LEAFMINER PARASITOID DIGLYPHUS-BEGINI (HYMENOPTERA, EULOPHIDAE)

Susceptibility of males and females of the Liriomyza leafminer parasitoid Diglyphus begini (Ashmead) to methomyl, oxamyl, fenvalerate, and permethrin was compared with laboratory bioassays. For each insecticide and five populations tested, males were more susceptible than females. Differences in LC50s between the sexes ranged from 1.3- to 15.7-fold and were greater in resistant compared with susceptible populations. Tibia length was significantly less for male than female D. begini. Size differences ranged from 1.1- to 1.2-fold. Piperonyl butoxide synergized oxamyl and fenvalerate in males and females, suggesting that oxidative detoxification was important in both sexes. The addition of piperonyl butoxide to oxamyl affected both sexes similarly. The synergistic effect of piperonyl butoxide with fenvalerate was significantly greater for females than males, suggesting greater oxidative detoxification of fenvalerate in females than males.