Synergistic effect of lactic acid with a chemosterilant metepa to the sound-attracted male mosquitoes

Abstract

Autochemosterilization of mosquitoes by a sound trap necessitated designing an improved formulation of chemosterilant for treatment at inside of the trap. When 18 chemicals including some putative mosquito attractants were screened in mixtures of hempa by contact test, lactic acid mixture gave significantly higher sterility than hempa to Culex pipiens molestus. Metepa was more effective and residual than hempa up to 5 days after treatment both in lactic acid mixture and metepa per se. Topical application of the mixture proved the synergistic activity of lactic acid with metepa. Gas chromatographic analysis of metepa showed that males took up 0.4 times less amount of metepa from the mixture-treated sound trap than the metepa-treated sound trap, because lactic acid was somewhat repellent to males. Nevertheless, the sterility of males was slightly higher with the mixturetreated trap than the metepa-treated trap.