Residual Activity of Insect Growth Regulators Against Stored-Product Beetles in Grain Commodities

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Abstract
The insect growth regulators (IGRs) BAY SIR 8514 [1-(4-trifluoro-methoxyphenyl)-3-(2-chlorobenzoyl)urea), diflubenzuron, methoprene, and MV-678 [2-methoxy, 9-( p -isopropylphenyl)-2,6-dimethylnonane] were evaluated for residual activity against two internal feeders, Rhyzopertha dominica (F.) and Sitophilus oryzae (L.) in stored grains for 1 year. The first three at 1 to 10 ppm each gave effective control (98 to 100%) of R. dominica in stored wheat, barley, and corn for more than 12 months posttreatment, and MV-678 was the least active. In wheat grain, BAY SIR 8514 at 0.1 and 0.5 ppm was effective against R. dominica for 4 and 6 months posttreatment, respectively. Diflubenzuron at 0.1 and 0.5 ppm provided 97 to 98% control for 6 months post treatment. The residual activity of methoprene at these lower concentrations did not result in appreciable control of R. dominica . Data on the residual activity of BAY SIR 8514, ditlubenzuron, and methoprene against S. oryzae in stored wheat showed that ditlubenzuron was more active than BAY SIR 8514 and methoprene. At 5 and 10 ppm, this compound gave 100% control at 2-week to 12-month posttreatment intervals. At 1 ppm its residual activity (93.7%) at 2-week intervals gradually increased to as high as 99.8% at 12 months posttreatment. BAY SIR 8514 at 1 ppm showed an almost similar trend in residual activity, ranging between ca. 70% control at 2 weeks post treatment and >99% control at 12 months post treatment. At 5 and 10 ppm, this compound provided 96 to >99% control at 2 weeks to 12 months post treatment. Methoprene tested at 1, 5, and 10 ppm against S. oryzae did exhibit residual action which increased with time. Its activity, however, was low, and even at 10 ppm it gave only 80 to 93% control at various intervals during the test period.

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