Efficacy of protectants against Callosobruchus phaseoli (Gyll.) and C. maculatus (F.) (Coleoptera: Bruchidae) in mungbeans

Abstract

The organophosphorus (OP) compounds chlorpyrifos-methyl, fenitrothion, methacrifos and pirimiphos-methyl, synthetic pyrethroids (SP) deltamethrin and permethrin, and the insect growth regulator (IGR) fenoxycarb were evaluated as protectants against Callosobruchus phaseoli (Gyll.) and C. maculatus (F.) in mungbeans (Vigna radiata (L.) Wilczek). Treated mungbeans were sampled for efficacy testing using C. phaseoli after various periods of storage in hot and humid conditions (30°C, 70% r.h.). Minimum effective application rates were determined for different periods of protection. During storage the OP compounds (chlorpyrifos-methyl, fenitrothion, methacrifos and pirimiphos-methyl) lost activity against C. phaseoli much faster than the SPs (deltamethrin and permethrin) and the IGR (fenoxycarb). Tests were carried out on mungbeans which were infested with C. phaseoli before treatment with pirimiphos-methyl, fenoxycarb or deltamethrin. These tests showed that immature insects in the treated beans were protected from insecticides. Finally, freshly-treated mungbeans were exposed to C. maculatus for comparison with the results for C. phaseoli. The four OP compounds, two SPs and the IGR tended to have similar potency against C. maculatus and C. phaseoli. © 1993.