Preliminary studies on the insecticidal activity and wash‐fastness of twelve pyrethroid treatments impregnated into bednetting assayed against mosquitoes

摘要

AbstractThe insecticidal properties of twelve pyrethroid preparations impregnated into polyester netting were compared, before and after washing, with a view to assessing their suitability for treating bednets (mosquito nets) in the field. Bioassays were carried out by exposing the mosquitoes,Anopheles gambiaeGiles sensu stricto andAedes aegyptiL. to netting with two concentrations of insecticide, on washed and unwashed samples, for 30 s and 3 min at different times after impregnation. Mortality was recorded after 24 h. Permethrin applied at 97°C at pH 3.4 resulted in increased uptake by polyester fibres. The performance of most insecticides on unwashed netting had not declined appreciably 12 weeks after impregnation. However, all the insecticides were depleted by washing. The treatments with best insecticidal activity after washing were cypermethrin, lambda‐cyhalothrin applied at ambient temperature and normal pH and permethrin applied in a hot acid soluti