Since the discovery of soybean aphid (Aphis glycines Matsumura) (Hemiptera: Aphididae) in North America in 2000, researchers have identified several major factors that contribute to the management of aphid populations. The major factors that have been identified are the top-down suppression of aphid populations by natural enemies, and the bottom-up effects of soil nutrition, specifically soil potassium. In addition to these factors, genes that convey aphid resistance have also been identified. We studied how several of these genes interacted with the ecosystem services of natural enemies, and how they preformed in potassium deficient soil. The overall number of natural enemies was no different between resistant and susceptible plots. There were significant differences in the density of certain taxa, corresponding with different aphid density in resistant and susceptible plots. There was no significant difference in the ecosystem services provided by natural enemies in resistant and susceptible plots. No significant difference in aphid populations was detected between plants grown in potassium deficient and potassium amended soil. Resistant plants had significantly lower aphid populations than susceptible plants in both potassium deficient and potassium-amended cages. We also used molecular markers to explore the relationships of aphid populations on resistant and susceptible soybean. We found significant impacts of geography on aphid populations and that populations of aphids from each resistant line were significantly different from the other resistant line. This helps us understand how host plant resistance can be effectively integrated in to current aphid management practices.
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