Effects of reduced risk-insecticides on the soybean (Glycine max) natural enemy community
Wayne J. Ohnesorg, firstname.lastname@example.org and Matthew E. O'Neal, email@example.com. Iowa State University, Entomology, 113 Insectary, Iowa State University, Ames, IA
Natural enemies are an important part of soybean aphid (Aphis glycines Matsumura (Hemiptera: Aphididae) management. Broad spectrum insecticides, like lambda-cyhalothrin, are frequently used to control soybean aphids but reduce natural enemy abundance. Insecticides considered reduced-risk when, by mode of action or method of contact, have limited exposure to non-target species. Our objective was to determine if reduced-risk insecticides have a limited impact on the natural enemy community in soybeans. During the 2005 and 2006 growing season we applied lambda-cyhalothrin (Warrior®) and several potential reduced-risk insecticide to small plots of soybeans with naturally occurring soybean aphid populations. Reduced-risk insecticides included; nicotinoid seed treatments imidacloprid (Gaucho®) and thiamethoxam (Cruiser®), a foliar applied imidacloprid (Trimax®) and foliar applied pymetrozine (Fulfill®). Products were chosen based on mode of contact (systemic; imidacloprid and thiamethoxam) and selectivity for aphids (pymetrozine). We monitored soybean aphids and associated natural enemies before application of the foliar applied insecticides and at a 3-week period post-application. Aphids and natural enemies were sampled by visual inspection of the plant and sweep-nets. Regardless of mode of action, foliar applied insecticides provided greater control of soybean aphids than seed treatment, which were not significantly different from our untreated plots. The foliar insecticide lambda-cyhalothrin had the greatest reduction in total natural enemies. Seed treatments, the foliar applied imidacloprid and pymetrozine had no observable effect on the natural enemy community, including Orius insidiosus (Hemiptera: Anthocoridae) a soybean aphid predator known to feed on soybeans during times of low prey availability.
Species 1: Hemiptera Aphididae Aphisglycines (soybean aphid)