Persistence and toxicity of dimethoate on wheat herbage and sweetclover herbage

Abstract

Dimethoate was applied at 35, 70, 125, 250, and 500 g/ha to sweetclover and the herbage collected for chemical analysis at 0.2 hours and 1, 3, and 5 days after application. Residues of dimethoate decreased quickly with time with 20% or less remaining after 5 days. Dimethoate was applied (420 g/ha) to wheat and the herbage was collected at 0.2, 2, 5, 12, 18, 24, 48, and 72 hours after application for both chemical and biological analysis. Chemical analysis of the wheat herbage indicated a 65 to 85% loss of dimethoate in the first 24 hours after spraying. Mortality of 2nd and 3rd instar nymphs of Melanoplus sanquinipes (Fabr.) eating the sprayed herbage decreased from an average of 55% to 19% in the same time period.

Key words:

• dimethoate
• wheat herbage
• sweetclover herbage
• persistence
• grasshoppers