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

The acetylcholinesterase in some resistant strains of Myzus persicae a nd its extremely close relative Myzus nicotianae showed marked insensi tivity to inhibition by the established carbamate pirimicarb (>100-fol d) and by triazamate, a novel triazole aphicide (>10-fold), that acts on the same target. There was no insensitivity to a range of other car bamate and organophosphorus insecticides. This resistance mechanism ap pears 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 targ et site mechanism, even when heterozygous, enhances the esterase-based resistance to pirimicarb and triazamate by 15- to 30-fold.(C) 1994 Ac ademic Press, Inc.