The soybean aphid Aphis glycines Matsumura (Homoptera: Aphididae) is an invasive species first discovered in North America in 2000, and now detected in 20 north central and northeastern states. Previous studies in Michigan have demonstrated that natural enemies significantly reduce A. glycines establishment and population growth. The objective of this study was to test the effect of natural enemies (top down) on soybean aphid populations on soybean produced under different agronomic practices, that may alter host plant quality (bottom up). Three agronomic treatments that represented a gradient of disturbance were tested at the Kellogg Biological Station – Long Term Ecological Research site: 1) standard levels of agrochemical inputs and tillage, 2) standard levels of agrochemical inputs, no tillage, and 3) no agrochemical input and standard tillage. The effect of natural enemies on aphid establishment was tested using exclusion clip cages, open clip cages, and no cage controls, within each agronomic treatment. Effects on aphid population growth were tested similarly but in 1 x 1 x 1 m cages. The predator community was sampled through pitfall traps and visual counts. We tested the expectations of lower aphid densities 1) when exposed to predation and 2) under no tillage conditions, and 3) higher aphid densities when agrochemical inputs were used, due to improved host plant quality. These results will provide basis for the selection of agronomic practices that maximize the effect of natural enemies and minimize potential for the development of soybean aphid outbreaks.
Species 1: Homoptera Aphididae Aphis glycines (Soybean aphid)
Species 2: Coleoptera Coccinellidae Harmonia axyridis
Species 3: Heteroptera Anthocoridae Orius insidiosus
Keywords: predation, agronomic practices
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