New esterase enzymes involved in organophosphate resistance in Culex pipiens (Diptera: Culicidae) from Guang Zhou, China.

Organophosphate (OP) insecticides have been used widely to control Culex pipiens L. populations and this has led to the emergence of OP-resistance. Predominantly, resistance in Cx. pipiens is caused by over-production of nonspecific esterases, such as Est beta 1(1) and Est alpha 2(1)/beta 2(1). These esterases confer multiple resistance to organophosphorus and carbamate insecticides. To define the esterases in Chinese Cx. pipiens, restriction fragment-length polymorphism analysis was performed at the esterase beta locus. A new esterase haplotype (Est beta 8) was found. Starch gel electrophoresis indicated that Est beta 8 was coelevated with a novel Est alpha 8. This article reports Est alpha 8/beta 8 esterase-mediated resistance in Cx. pipiens complex.