Comparative analysis of mosquito (Diptera: Culicidae: Aedes aegypti Liston) responses to the insecticide Temephos and plant derived essential oil derived from Piper belle L.

Resistance to treatments with Temephos or plant derived oil, Pb-CVO, between a field collected Wild Strain (WS) and a susceptible Laboratory Strain (IS) of Ae. aegypti were measured. The Temephos (0.1 mg/L) showed the greatest percentage of mosquito mortality compared to Pb-CVO (1.5 mg/L) in IS Ae. aegypti. However, WS Ae. aegypti was not significantly affected by Temephos (0.1 mg/L) treatment compare to the Pb-CVO (1.5 mg/L). However, both strains (IS and WS) when treated with Pb-CVO (1.5 mg/L) displayed steady larval mortality rate across all instars. The LC50 of Temephos was 0.027 mg in IS, but increased in WS to 0.081 mg/L. The LC50 of PbCVO treatment was observed at concentrations of 0.72 and 0.64 mg/L for LS and WS strains respectively. The enzyme level of alpha- and beta-carboxylesterase was reduced significantly in both mosquito strains treated with PbCVO. Whereas, there was a prominent deviation in the enzyme ratio observed between IS and WS treated with Temephos. The GST and CYP450 levels were upregulated in the IS, but decreased in WS, after treatment with Temephos. However, treatment with Pb-CVO caused both enzyme levels to increase significantly in both the strains. Visual observations of the midget revealed cytotoxicity from sub-lethal concentrations of Temephos (0.04 mg/L) and Pb-CVO (1.0 mg/L) in both strains of An aegypti compared to the control. The damage caused by Temephos was slightly less in WS compared to LS mosquito strains.