Differential selection of malathion resistance in Anopheles culicifacies A and B (Diptera: Culicidae) in Haryana State, India.

In November 1989, for the first time after the introduction of malathion spray in 1982, increased densities of Anopheles culicifacies Giles s.l. were observed in Chhatera and Barota, two villages in Halalpur block in Sonepat District, Haryana State, India. In bioassay tests against the diagnostic dose of malathion (5% for 1 h), 41-47% of mosquitoes survived. An culicifacies populations in this area comprise two sibling species, A and B. Differential malathion resistance was observed; in species A it was 2-9% and in species B 62-66%. Likewise, species A was found to be more susceptible to DDT than was species B. The possible use of DDT spray to delay the onset of malathion resistance is discussed.