Resistance to DDT in the Adult Codling Moth and Reference Curves for Guthion and Carbaryl1

Abstract

Resistance to DDT in the codling moth, Carpocapsa pomonella (L.), may be readily detected by topical application to the adult moth. The adult exhibits a high degree of detectable resistance indicating that selection pressure is high against the moth stage. Standard procedures, involving exposure to residues on fruit, fail to detect resistance in the newly hatched larvae of the same strains. Reference curves on a nonresistant population are presented for both male and female moths for DDT, Guthion® ( O,O -dimethyl S -( 4-oxo-1, 2,3-benzotriazin-3( 4H )-ylmethyl phosphorodithioate) and carbaryl, and curves for both sexes in two DDT-resistant populations are presented. Topical application provides reproducible data readily and is superior in convenience, rapidity, reproducibility, and sensitivity to techniques used which involve exposing newly hatched larvae to residues. Because of its superior reproducibility as compared with larvicidal trials, this procedure is believed to be useful also in screening for toxicity to lepidopterous pests.