Susceptibility of Pakistani populations of cotton aphid Aphis gossypii (Homoptera: Aphididae) to endosulfan, organophosphorus and carbamate insecticides

The Pakistani field populations of Aphis gossypii were assessed from 1996 to 2004 for their susceptibility to endosulfan, organophosphates (monocrotophos, dimethoate, profenofos, chlorpyrifos, quinalphos, parathion-methyl, pirimiphos-methyl and ethion) and carbamates (carbaryl, methomyl, thiodicarb, furathiocarb and carbosulfan) using a leaf-dip bioassay method. Generally, there was a very low resistance to endosulfan, monocrotophos, profenofos, chlorpyrifos, quinalphos, pirimiphos-methyl, carbaryl and methomyl, and a low to moderate resistance to dimethoate, parathion-methyl and thiodicarb. Some of the populations had a very high resistance to parathion-methyl, ethion and thiodicarb. However, no resistance was found to the carbamate aphidicides furathiocarb and carbosulfan. Correlation analysis demonstrated positive correlation of LC50s within but not between the two insecticide groups (1) endosulfan, profenofos, chlorpyrifos and parathion-methyl and (2) monocrotophos, dimethoate, pirimiphos-methyl, ethion, carbaryl, methomyl and thiodicarb. This pattern of cross-resistance among organophosphates and carbamates, which are normally considered to have the same mode of action, is very useful for devising an insecticide resistance management strategy to mitigate resistance problems in A. gossypii and deserve further investigation at the resistance mechanism level.