EFFICACY AND SUBLETHAL EFFECTS OF MOSQUITO COILS ON AEDES AEGYPTI AND CULEX QUINQUEFASCIATUS (DIPTERA: CULICIDAE)

Abstract:
Mosquito coils with the active ingredient d-allethrin (0.2% w/w), and d-trans allethrin (0.1% w/w) together with blank coils were tested in the laboratory against Aedes aegypti (Linn.) and Culex quinquefasciatus Say of different ages and physiological condition, using a test method of the Standard and Industrial Research Institute of Malaysia (SIRIM). Results indicated that Ae. aegypti was more susceptible than C.Y. quinquefasciatus. The blank coil caused neither significant knockdown nor mortality of mosquitoes, while coils containing either d-allethrin or d-trans allethrin provided adequate knockdown of mosquitoes, but with low mortalities for both Ae. aegypti and Cx. quinquefasciatus mosquitoes below 10 days of age. The susceptibility of mosquitoes increased with age as indicated by a decrease in KT50 and increase in mortality of female mosquitoes tested for both species. This study also indicated that bloodengorged mosquitoes were more difficult to be knocked down, but easier to kill than non blood-engorged mosquitoes. However, susceptibility of mosquitoes to coils was not affected by oviposition. The survivors of mosquito coil exposure were used for sublethal effects studies, concentrating on the longevity and fecundity of treated individual and progeny survival. The longevity of both species decreased more than 40% after exposure to mosquito coils containing either d-allethrin or d-trans allethrin. The percentage of bloodengorgement activity for Ae. aegypti and Cx. quinquefasciatus was reduced to less than 55% and 15%, respectively after a 20 minutes exposure to coils containing either one of the active ingredients. Furthermore, C.Y. quinquefasciatus also showed a decrease in blood-engorgement ability (<40%) after being exposed to a blank coil. Nevertheless, the number of eggs oviposited by the treated females, egg hatchability, pupation rate and adult emergence rate were not affected if the mosquitoes were still able to blood-engorge.