Chlorpyrifos-methyl: Doses that Protect Hard Winter Wheat Against Attack by Stored-Grain Insects2

Abstract

Chlorpyrifos-methyl was applied to cleaned, hard winter wheat as a water emulsion at doses ranging from 1–10 ppm AI. The effectiveness of residues in samples withdrawn at intervals during a 12-mo storage showed that initial applications of 3 or more ppm AI controlled rice weevils, Sitophilus oryzae (L.), granary weevils, S. granarius (L.), and maize weevils, S. zeamaiz Motschul-sky. In contrast, a dose as high as 8 ppm was required to kill ca. 90% of the lesser grain borers, Rhyzopertha dominica (F.), 83% of the confused flour beetles, Tribolium confusum , Jacquelin duVal, and 98% of the red flour beetles, T. castaneum , (Herbst) 12 mo after application.