CURRENT STATUS OF ANOPHELES-STEPHENSI RESPONSE TO VARIOUS INSECTICIDES IN SOME AREAS OF THE THAR DESERT

Investigations on the current response of A. stephensi. to six insecti cides viz. DDT, dieldrin, malathion, fenitrothion, propoxur and permet hrin, were carried out in 3 districts i.e., Barmer, Jodhpur and Pall, of the Thar desert. The species was found resistant to DDT and dieldri n, partially resistant to malathion and susceptible to fenitrothion, p ropoxur and permethrin. Dieldrin and malathion resistance has been det ected for the first time in the Thar desert. Lethal concentrations (LC (50) & LC(95)) of DDT and dieldrin and lethal exposure times (LT(50) & LT(95)) of malathion, fenitrothion, propoxur and permethrin have been determined. In some areas, the differences in LC(50) and LT(50) value s of tested insecticides, except fenitrothion, were found statisticall y significant. Chi-square and regression tests have revealed the homog eniety and linear trend respectively in the response of A. stephensi t o insecticides. The findings of the study indicate that organochlorine compounds can be used alternately in the spray operations.