Influence of insecticide Bacillus thuringiensis subsp. israelensis treatments on resistance and enzyme activities in Aedes rusticus larvae (Diptera: Culicidae)

The bacterio-insecticide . Bacillus thuringiensis subsp. . israelensis (. Bti) represents currently a safe alternative to chemical insecticides in mosquito-borne diseases control and is intensively used worldwide. In the French Rhône-alpine mosquito . Aedes rusticus Rossi, several genomic signatures of selection were detected in populations treated for more than 15. years with . Bti. In this study we investigated whether detoxifying enzyme activities such as cytochromes P450, esterases and glutathione S-transferases can play a role in . Bti resistance mechanisms in these populations. To examine the effect of . Bti treatment on larval resistance and detoxifying enzyme activities, . Bti mortality and enzymatic activities were measured in treated and untreated sites coming from four different locations in the Rhône-Alpes region. The results revealed a significant global decrease in . Bti mortality in treated populations, but showed low resistance ratio up to 7.9-fold between treated and untreated sites. A positive correlation has been observed between larval resistance to . Bti and glutathione S-transferase activities, raising the question of its potential role in . Bti resistance. A better understanding of all the mechanisms potentially involved in . Bti resistance is necessary to insure the long-term efficiency of this bacterio-insecticide. © 2012 Elsevier Inc.