Degradation and Efficacy of Deltamethrin + Chlorpyrifosmethyl and Cyfluthrin + Chlorpyrifos-methyl as Protectants of Wheat Stored in Southeast Georgia1

Abstract

Soft red winter wheat (27.27 kg replicates) treated with combinations of deltamethrin + chlorpyrifos-methyl, with and without piperonyl butoxide, and cyfluthrin, applied alone or with either chlorpyrifos-methyl or piperonyl butoxide, was stored from 15 May 1992 to 9 February 1993 (6 chemical treatments and an untreated control). Each replicate was artificially infested with 50 adult lesser grain borers, Rhyzopertha dominica (Fab.), and 50 adult rice weevils, Sitophilus oryzae (L.), upon initial storage, sampled with probe traps at monthly intervals, and subsequently reinfested. Trap catch of lesser grain borer was always 0, except for two traps at month 4 that contained one adult in each trap. Maximum population levels of rice weevil and a natural infestation of the red flour beetle, Tribolium castaneum (Herbst), occurred at month 5. Trap catch of these two species in the chemical treatments averaged 2.2 to 34.0 and 0.0 to 19.5 live adults per trap, respectively. From months 4 to 9, the percentage of insect-damaged kernels averaged 4.0 to 5.5% in wheat treated with 0.25 ppm deltamethrin + 6.0 ppm chlorpyrifos-methyl + 4.0 ppm piperonyl butoxide. Maximum kernel damage in the other chemical treatments was 3.2%.