Toxicity of dichlorvos vapour to insects in aerated and non-aerated wheat and comparison of the vapour action of dichlorvos and malathion

Abstract

Bioassay tests demonstrated the potent vapour toxicity of dichlorvos to Sitophilus oryzae and Rhyzopertha dominica. On freshly treated wheat at 20°C the lethal effect of dichlorvos was predominantly due to a mobile form of dichlorvos. This contrasts with the action of malathion. Dichlorvos vapour at toxic concentrations was moved through grain for up to 4 m using air flows comparable to those used in aeration of bulk stored wheat. There was a marked increase in efficiency of dichlorvos under forced air-flow conditions. Effect of air flow on movement of dichlorvos through wheat is discussed quantitatively.