none The study looked at the residual effect of some commonly used insecticides (e.g. Ambush, Diazinon and Nicotine) on the mortality and behaviour of Aphidius colemani Viereck, in particular, whether the latter changed in the presence of sub-lethal doses of the pesticides. It was found that even at half concentration, the residual effect of all three insecticides lasted more than the official recommended period, i.e. 14, 14 and 2 days for Ambush, Diazinon and Nicotine respectively, in that they all modified the on-plant foraging behaviour of the parasitoid. The results for Diazinon suggested few effects after 20 days but for Ambush the average net speed, time spent searching and total time spent on the leaf disc even after 20 DAS was significantly lower. For Nicotine only the number of entries was significantly lower at 4 DAS. Nutrition; Feeding behaviour; Abiotic factors; Chemical factors Aphidius colemani (Aphidiidae); Foraging, relationships; Fertilizers and pesticides; Insecticides