Ashley Dean, Iowa State University, Department of Entomology
M.Sc. defense seminar.
Abstract. Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), has been a prominent insect pest in the upper Midwest since 2000. Insecticides are the primary management tactic for this pest; however, soybean aphid-resistant varieties are available but without herbicide tolerance. This may be a significant barrier to adoption since farmers rely on herbicide-tolerant varieties for convenient weed control. In recent years, farming has become less profitable due to declining market value, higher input costs, and unpredictable weather. The impact of soybean aphid has increased due to the recent occurrence of pyrethroid resistance, further reducing profit margins for soybeans. We conducted both a field experiment and an economic analysis to compare the effectiveness of soybean aphid management tactics and their profitability for Midwestern farmers, and evaluated how insecticide resistance could impact profitability in the future. Our field research demonstrated that aphid-resistant varieties provide protection from soybean aphid in all environments tested and provide yield protection equal to insecticide applications. Our model also predicted these relationships, but revealed that resistant varieties provide greater net revenue compared to insecticide applications. Further, our model indicated that insecticide resistance poses a major threat to profitability and will be expensive for farmers that manage soybean aphid with insecticides.