TOXICITY AND PERSISTENCE OF BIOETHANOMETHRIN AND DIMETHOATE IN THE CONTROL OF GRASSHOPPERS (ORTHOPTERA)

Abstract

AbstractIn laboratory tests Bioethanomethrin was more than 20 times as toxic as dimethoate when sprayed on nymphs of Melanoplus sanguinipes (Fabr.). Its residual effect on grasshoppers fed treated foliage was relatively insignificant. Toxicity in small field experiments resulted mainly from spray hitting the grasshoppers rather than from their walking or feeding on treated foliage. For 8 days the dimethoate treatment kept numbers of invading grasshoppers significantly lower than those in untreated plots, whereas Bioethanomethrin was ineffective after 2 days. The results indicate that the residual toxicity of the insecticides was of secondary importance in reducing the initial infestation; however, residues do offer a margin of safety against such hazards as poor application, invasion from outside, or continued hatching after treatment.