BIOLOGICAL-ACTIVITY OF IGRS AGAINST 4 STORED-PRODUCT COLEOPTERANS

Four insect growth regulators (IGR), BAY SIR 8514 [(1-4-trifluoromethoxyphenyl)-3-(2-chlorobenzoyl) urea], diflubenzuron, methoprene and MV-678 [2-methoxy-9-(p-isopropylphenyl)-2,6-dimethylnonane], applied at 5 ppm to wheat flour or grain, were evaluated against Oryzaephilus surinamensis (L.), Tribolium castaneum (Herbst), Rhyzopertha dominica (F.) and Sitophilus oryzae (L.). BAY SIR 8514 and diflubenzuron were highly active against the eggs and younger larvae of O. surinamensis, T. castaneum and R. dominica. Methoprene, besides its ovicidal action against O. surinamensis and R. dominica, caused substantial mortality in the full-grown larvae of the 3 spp. BAY SIR 8514 and methoprene also affected the subsequent progeny production of parent adults preexposed to IGR-treated food for 2 wk. MV-678 was the least active compound tested. Diflubenzuron and methoprene had no adverse effects on the development of S. oryzae inside grain kernels infested with parent adults 1 day after grain was treated. In grain treated with BAY SIR 8514, diflubenzuron and methoprene, and infested with this insect after 12 mo. of posttreatment storage, the development of this species was arrested significantly. BAY SIR 8514 and diflubenzuron were more active against the eggs and younger larvae, with methoprene showing activity against all stages from egg to preemergent adults of this species. In testing IGR against internal feeders, it is important to allow for penetration of the active ingredients into the inner portions of grain kernels before assessing effects.