Survival and behavioral disorders of Aedes aegypti larvae exposed to different insecticides

The yellow fever mosquito Aedes aegypti plays a key role in the transmission of human pathogens, so its control through the use of insecticides is of major importance.  Larvae (L3) were exposed to the following insecticides: azadirachtin (0, 0.1, 0.5, 1, 10 ppm), imidacloprid (0, 0.15, 1.5, 3, 6, 15 ppm), spinosad (0, 0.025, 0.05, 0.1, 0.5, 1, 4, 10 ppm) and deltamethrin (0, 0.001, 0.01, 0.05, 0.1, 0.5, 1.0, 10 ppm) diluted in distilled water. After exposition we assessed the adult mosquito emergence, and also the L3 locomotion changes with the aid of the software Videotrack 3.0 (Viewpoint Life Science). The insecticides reduced the survival in a concentration-dependent fashion, whereas the higher toxicity was found in deltamethrin (χ²=382.66, df=7, P<0.001), followed by spinosad (χ²=837.94, df=7, P<0.001), imidacloprid (χ²=238.65, df=5, P<0.001) and azadirachtin (χ²=58.20, df=4, P<0.001). Linear regression analyses showed that the swimming distance and resting time were significantly altered by deltamethrin (F=13.02, p<0.001, R²=0.43), imidacloprid (F=6.12, p=0.01, R²=0.25) and spinosad (F=76.78, p<0.001, R²=0.70). L3 exposed to insecticides moved up straight at low speed without bending their body (non-wriggling), different of the wriggle swim behavior reported for the control. The use of sublethal insecticide doses on A. aegypti can disrupt the mosquito's life cycle by means reducing the adult emergence and L3 behavior.