Effect of some organophosphate insecticides on acetylcholinesterase of adult Coccinella septempunctata (Coccinellidae)

The in vitro enzyme activity of head homogenates of Coccinella septempunctata from different habitats (wheat, barley, rye and set-aside fields in Belgium and Hungary) and the effect of in vivo surface contact treatments with organophosphorous active ingredients on the same species were investigated. The in vitro studies indicated that the acetylcholinesterase (AChE) of C. septempunctata was less sensitive to inhibition by paraoxon than by malaoxon in the case of each population. The differences found between parathion and malathion treatments in in vivo testing were not significant. The inhibition process of paraoxon suggests that the seven-spot ladybird may have at least two AChEs responding differently for the paraoxon inhibition.