Resistance development to bioinsecticides in Aedes aegypti (Culicidae: Diptera), the vector of dengue fever in Saudi Arabia.

A laboratory strain of Aedes aegypti (L) was subjected repeatedly to larval selection pressure with two bacterial insecticides, spinosad (Saccharopolyspora spinosa) and bacilod (Bacillus thuringiensis israelensis). The results indicated that the mosquito Ae. aegypti acquired low resistance to spinosad and bacilod by about 3.1 and 2.4-fold, respectively, due to selection pressure for fifteen successive generations. The slope values of the selected strains were increased gradually from one generation to the next, indicating moderate homogeneity between individuals in their response to the test bio-insecticide. Moreover, larval selection with current bacterial bioinsecticides prolonged the time required to digest a blood meal. It showed an evident decrease in the reproductive potential of adult mosquitoes surviving selected larvae.