Resistance spectra and allelism of chlorpyrifos resistance factors in Culex quinquefasciatus populations from colombo and Dar-es-Salaam

Abstract

The induction of resistance in the urban pest mosquito, Culex quinquefasciatus, to chlorpyrifos and chlorfenvinphos and the cross-resistance spectra of these selected lines to propoxur and a number of organophosphate insecticides was studied. Distinct genetic factors governing intermediate (R1) and high (R2) levels of larval resistance to organophosphates were found to be allelic according to the single locus, multiple aliele hypothesis. Adults were less susceptible to malathion and fenitrothion after larval selection with chlorpyrifos, but the degree of resistance was found to be much less than that in the larvae. The implications of these results for the control of C. quinquefasciatus in Dar-es-Salaam, Tanzania, is discussed.