Assessment of insecticide susceptibility of Liriomyza trifolii (Burgess) and its three parasitoids by laboratory bioassays

Abstract

The susceptibility of adults of the leafminer, Liriomyza trifolii (Burgess) and its three parasitoids (Chrysocharis pentheus (Walker), Hemiptarsenus varicornis (Girault), and Neochrysocharis formosa (Westwood)) to four conventional insecticides (malathion, permethrin, imidacloprid, and emamectin benzoate) was examined in the present study. To this end, a laboratory bioassay was employed using either one or two concentrations of each of the commercial insecticides. Low mortalities (8.5% and 6.8%) were observed in leafminers treated with malathion (3,000-fold dilution) and imidacloprid (2,000-fold dilution). In contrast, moderate mortalities (63.3% and 44.4%) were observed in leafminers treated with permethrin (5,000-fold dilution) and emamectin benzoate (2,000-fold dilution). High mortality (87.3%–100%) of parasitoids was observed for all the insecticides evaluated. The results of the present study suggest that large differences in insecticide susceptibility exist between the leafminer and its parasitoids. This information could be exploited for better management of L. trifolii.