This study determined the effects of key insecticides on Trichogramma chilonis parasitism in field trials. It showed that the number of large cabbage moth (LCM) eggs in Chinese cabbage was significantly reduced after application of AttackTM (p: 0.001) and EntrustTM (p: 0.00) but not after spraying with OrtheneTM (p: 0.09) and DipelTM (p: 0.485). Negative effects of insecticides were observed on the parasitism rate of T. chilonis and LCM egg masses, which were more likely to be only partially parasitised after an insecticide application. AttackTM and EntrustTM adversely affected T. chilonis parasitism rates of LCM eggs. However, the effect of OrtheneTM and DipelTMdid not significantly differ from each other and could be safer to the parasitoid since both reduced T. chilonis parasitism the least. The distribution of LCM eggs in the cabbage leaves was also affected by the insecticides; before insecticide application the majority of egg masses were concentrated in the upper surface of the foliage but after insecticide sprays most of the egg masses were found in the lower surface of the foliage. This study suggests that OrtheneTM and DipelTMhave no effect on the parasitism but DipelTM was found safer to the parasitoid and it could be considered for inclusion in IPM programmes that depend on T. chilonis parasitism of LCM.
