Induced Disulfoton Resistance in Greenbugs (Homoptera: Aphididea)

Abstract

Field studies were done to determine whether continuous exposure to the systemic insecticides al bicarb, carbofuran, disulfoton, and terbufos would induce or select for insecticide-resistant green bugs, Schizaphis graminum (Rondani). The extent of resistance was determined with a surface residue bios say for each of the insecticides. In field experiments, green bug populations exhibited 21- to 104-fold increases in resistance to disulfoton. Green bugs exposed to the other insecticides did not exhibit significant increases in resistance. Greenhouse studies were done to determine if disulfoton resistance resulted from a change within a genotype (green bug clone) or was simply the result of selection of resistant genotypes from a genetically diverse population. Green bugs originating from a single aphid susceptible to insecticides developed 65- to 300-fold increases in resistance. Similar results were obtained when the study was repeated with progeny from a different green bug. These results indicate that resistance developed within green bug clones after exposure to disulfoton for 3 wk or longer. When resistant green bugs were tested for cross-resistanceto carbofuran, dimethoate, malathion, and terbufos, a significant increase in cross-resistance to dimethoate (nine-fold) and terbufos (two-fold) was observed, but cross-resistance to carbofuran and malathion was not significant.