Development of resistance and cross‐resistance in fenvalerate and deltamethrin selected strains of <i>Spodoptera littoralis</i> (Boisd.)

Abstract

Abstract Resistances of 33‐ and 27‐fold to the pyrethroids fenvalerate and deltamethrin, respectively, have been induced in larvae of the Egyptian cotton leafworm Spodoptera littoralis (Boisd.) by selection of two subcolonies of a field population in the laboratory. Selected strains showed relatively high levels of resistance (11‐ to 36‐fold) to all the tested pyrethroids, moderate levels of cross‐resistance (3‐ to 13‐fold) to DDT and the carbamate aminocarb, and a slight increase in tolerance levels to endrin and lindane. The pyrethroid‐resistant strains, by contrast, manifested no cross‐resistance to the organophosphorus compounds that were tested. Moreover, a negative crossresistance was observed in the pyrethroid‐resistant strains to dicrotophos, methamidophos and the carbamate methomyl.