Susceptibility status of vectors of Japanese encephalitis to insecticides in south Arcot and Tirunelveli districts of Tamil Nadu.

Villages in South Arcot and Tirunelveli districts with high incidence of Japanese Encephalitis were selected for the study of insecticidal resistance to vectors. Culex vishnui and Anopheles hyrcanus group were found to be resistant to DDT (4 per cent for 60 min. exposure) and dieldrin (0.4 per cent for 60 min. exposure) but susceptible to Malathion (5 per cent for 60 min. exposure). So far, this is perhaps the first report of Anopheles hyrcanus group resistant to DDT and dieldrin to be reported from this area. The resistance may be due to extensive use of DDT and HCH for agricultural purposes.