The soybean aphid is an economically damaging pest throughout much of the North Central United States. Soybean aphids are capable of reaching densities of >1,000 per plant in the field and can reduce soybean yields by 14-40%. Since its discovery in North America in 2000, economically damaging populations have developed in parts of Iowa in seven of the past eleven years. Soybean aphid-resistant soybean varieties are a new management tool for farmers. These varieties incorporate one or more genes conferring resistance to the soybean aphid. At least four genes conferring resistance to the soybean aphid have been identified: Rag1, Rag2, Rag3, and rag4. These genes suppress aphid growth and reproduction. This causes aphid populations to develop at a much slower rate than when feeding on susceptible plants, often preventing populations from reaching economically damaging levels.
Our laboratory is researching the efficacy of the Rag1 and Rag2 genes for soybean aphid control. We are interested in how these genes suppress aphid populations and how they may fit into current soybean aphid management practices. Specifically, we are investigating the efficacy of insecticidal seed treatments for soybean aphid-resistant varieties. We are also studying how the current soybean aphid predator community responds to these resistant varieties and how predators may contribute to increasing aphid population suppression on resistant varieties.
A major focus of current research is on the efficacy of combining both the Rag1 and Rag2 genes in a single soybean line for improved soybean aphid management. Specifically, we are interested in the benefits of two-gene lines for aphid population suppression, yield protection, and insect resistance management. Insect resistance management is especially important as soybean aphids capable of overcoming the Rag1 gene and Rag2 gene (termed resistant biotypes) have already been identified. The long-term success of soybean aphid host plant resistance as a management tool will depend on limiting the build-up of these resistant biotypes.