Two organophosphorus insecticides Diazinon (Nasrcidol EC 60%) and Malathion (Agrothion EC 57%) that recommended for controlling dipterous leafminers were evaluated for their effects on the population of Liriomyza trifolii and its associated parasite, during all parasitoid season (2000-2001). Both tested treatments caused decrease in the population density of Liriomyza trifolii. Comparing the effect of the two selected organophosphorus insecticides (Nasrcidol EC 60% and Agrothion EC 57% ) Nasrcidol EC 60%: was relatively more toxic and effective than Agrothion EC 57% in the first and second spray in controlling Liriomyza trifolii population on broad bean plant and slightly less toxic on its parasitoid Diglyphus isaea. From this study it could be concluded that both Nacrcidol EC 60 % caused excellent control of the leafminer and exhibited selectivity effect on the parasitoid.