Toxic and biochemical effects of imidacloprid and tannic acid on the Culex pipiens larvae (Diptera: Culicidae)

Abstract

Resistance of mosquitos to pyrethroid, organophosphate, and carbamate created the need for alternative insecticides. Therefore, 3rd larval instar of Culex pipiens was tested with different concentrations of the technical grade insecticides, imidacloprid and tannic acid. Biochemical assays were performed on the same populations of Culex pipiens to determine activities of acetylcholinesterase (AChE) and adenosine triphosphatase (ATPase) enzymes. The bioassay test showed that Cx. pipiens larvae were susceptible to imidacloprid than tannic acid. Concentrations of 0.01, 0.015, 0.02, 0.04 and 0.05 ppm imidacloprid produced experimental mortalities of 18.5, 31.67, 45, 83.33 and 90%, respectively. Tannic acid in the concentrations of 2500, 5000, 10000, 20000 and 40000 ppm produced experimental mortalities of 13.33, 38.33, 46.67, 85 and 98.33%, respectively. The biochemical assays showed that imidacloprid significantly (P<0.01) decreased the activity levels of both AChE and ATPase, while tannic acid didn’t show any significant difference on both enzymes compared to the control group.