Studies on contact toxicity-Part IV

Abstract

The use of starch and a mixture of glue and potassium dichromate as pretreatment for the enhancement of the residual activity of DDT has been investigated using mosquitoes, Cluex fatigans Weid. and flies, Musca nebulo Linn. The DDT deposits were derived either from an emulsifiable concentrate or a water dispersible powder concentrate. As substrate, cement, brick and mud surfaces were investigated both as they were in the lime-washed conditions. Pretreatment with glue-dichromate considerably enhanced the residual activity of DDT against both the species of insects on all the three surfaces and proved very much superior to pretreatment with starch. The deposits derived from DDT emulsion showed residual activity for a longer period than those derived from DDT water dispersible powder on mud surfaces pretreated with glue-dichromate.