Quantitative analysis of vector behavior following subacute exposure to prallethrin

The synthetic pyrethroid, prallethrin, is an active ingredient in a widely marketed ultralow volume (ULV) mosquito adulticide. Volatilized prallethrin is intended to stimulate mosquito flight, increasing overall effectiveness of the adulticide.  However, field tests using volatilized prallethrin had not produced significant differences in mosquito trap catches leading us to question the actual efficacy of prallethrin’s behavioral effects. We thus conducted laboratory tests of prallethrin’s effect on flight behavior of adult female Asian tiger mosquitoes (Aedes albopictus).  Mosquitoes were divided into three groups; a control, those exposed to volatilized prallethrin, and those exposed to a liquid spray calibrated to simulate a ULV application at label rates.  After 15 min, mosquito behavior in an air stream of 0.5m/s was recorded  and analyzed using motion-tracking software. No significant differences in flight behavior were found between controls and treated mosquitoes exposed to volatilized prallethrin, confirming the field results. ULV-sprayed mosquitoes exhibited an approximate 3-fold increase in the number of flight events, turned 3.1 times more frequently, traveled 4.8 times farther, and flew 9.3 times faster than controls—a significant difference in locomotor stimulation response that would increase exposure to a ULV spray cloud. However, our results show that volatilization alone is insufficient to increase ULV efficacy in the field. These results suggest that incorporating a more volatile flight stimulant into ULV adulticides would provide a measurable improvement in mosquito control.