The Correlation of bioassay and Acetylcholinesterase Activity in Propoxur-resistant,DDVP-resistant and Cypermethrin-resistant Culex pipiens pallens

Objective To explore the correlation of the resistance of Propoxurresistant,DDVPresistant and Cypermethrinresistant Culex pipiens pallens strains with Acetylcholinesterase(AChE) activity. Methods WHO bioassay and microplate method were used for the tests. Results The resistance indices of the three resistant strains became increased with the extension of generations during the 43generations' insecticide resistance selection. The average AChE inhibition rate of Propoxurresistant strain decreased with the extension of generations and the individual frequency of those with inhibition rate no less than 30% was the highest in the three resistant strains, followed by DDVPresistant strain, showing a correlation. The results were consistent basically with those of bioassay. The AChE activity in Cypermethrinresistant strain was similar to that of the susceptible strain. Conclusion The AChE activity showed a correlation with the resistance of Cx.pipiens pallens to carbamates and organophosphorus insecticides,and little with that to pyrethroids.