The influence of ambient temperature on the susceptibility of Aedes aegypti to the pyrethroid insecticide Permethrin
Whiten, Shavonn Reezale
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Insecticides are the most common management strategy used for the control of mosquitoes. Changes in ambient temperature can alter the toxicity of insecticides to ectothermic organisms. Studies show organophosphate insecticides exhibit a positive correlation between ambient temperature and mortality for many insect species, and carbamate insecticides exhibit a slightly negative to positive correlation between ambient temperature and mortality. Pyrethroid insecticides exhibit a distinctly negative correlation between increasing ambient temperature and mortality for insects. However, this relationship has not been systematically studied for adult mosquitoes. Therefore, we examined the influence of temperature on the susceptibility of adult Aedes aegypti (Diptera: Culicidae) when exposed to permethrin. Dose-response probit regression lines and the median lethal concentration, LC50, were estimated for adult Ae. aegypti when exposed to eight concentrations of permethrin (ranging from 0.06 - 0.58 ng/cm 2) at each of the following temperatures, 16, 23, 26, 30, 32, and 34 °C for 24 hours in bottle assays. The estimated LC50 for each temperature was 0.25, 0.34, 0.36, 0.48, 0.26, 0.31 ng/cm 2, respectively. Results indicated a negative correlation between temperature and mortality from 16 °C to 30 °C, a positive correlation between temperature and mortality from 30 °C to 32 °C, and a negative correlation between temperature and mortality from 32 °C to 34 °C. Most important, the largest negative temperature coefficient (-1.92) was observed at 30 °C. If mosquito populations are expanding in space and time because of increased temperatures due to global warming and cannot be managed as effectively with pyrethroids, the spread of mosquito-borne diseases may pose considerable risk to public health.