INSECTICIDE-INSENSITIVE ACETYLCHOLINESTERASE CAN ENHANCE ESTERASE-BASED RESISTANCE IN MYZUS-PERSICAE AND MYZUS-NICOTIANAE

The acetylcholinesterase in some resistant strains of Myzus persicae and its extremely close relative Myzus nicotianae showed marked insensitivity to inhibition by the established carbamate pirimicarb (>100-fold) and by triazamate, a novel triazole aphicide (>10-fold), that acts on the same target. There was no insensitivity to a range of other carbamate and organophosphorus insecticides. This resistance mechanism appears to be rare at present and was only found in a heterozygous form associated with the commonly occurring elevated E4/FE4 esterases that confer broad cross-resistance to many aphicides. This insensitive target site mechanism, even when heterozygous, enhances the esterase-based resistance to pirimicarb and triazamate by 15- to 30-fold.(C) 1994 Academic Press, Inc.