Comparative susceptibility of two Japanese encephalitis vectors from Mysore to six insecticides

Larval populations of Culex tritaeniorhynchus and C. fuscocephala from Mysore city were tested for their susceptibility against two pyrethroids viz., cypermethrin and deltamethrin and four organophosphorus (OP) compounds viz., fenthion, fenitrothion, temephos and malathion. The investigations revealed that, among the pesticides tested, efficacy of pyrethroids was very high as compared to OP compounds. C. tritaeniorhynchus was found to be highly tolerant to all the insecticides used. It registered 4.0, 6.5, 17.0, 6.5, 14.0 and 1.5 times more tolerance than C. fuscocephala to cypermethrin, deltamethrin, fenthion, fenitrothion, temephos and malathion respectively in terms of the LC50 value. Further studies are needed to determine the development of resistance if any, by C. tritaeniorhynchus, an important JE vector in Karnataka.