Management options for insecticide-resistant soybean aphid: Effectiveness of a novel insecticide and implementation of host plant resistance

Abstract

Management of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae) is threatened by a limited number of insecticide groups and evolution of resistant to one of the commonly used groups (i.e., pyrethroids). There is a need to evaluate additional chemical and non-chemical tools for management of soybean aphid. Using a leaf-dip bioassay, susceptibility of several populations of soybean aphid to afidopyropen was assessed during 2017 and 2018. Variation in susceptibility was found among populations with concentrations of afidopyropen necessary to kill 50% of a population (LC50) for soybean aphid adults ranging from 0.0013 to 0.40 mg a.i. per liter. A greenhouse experiment and field experiments were used to assess movement and spatial pattern of soybean aphid on aphid resistant plants with Rag genes. More movement of soybean aphid was found in aphid-resistant varieties (i.e., Rag1, Rag1+Rag2) than aphid-susceptible soybean. However, under field conditions, the spatial patterns of soybean aphid in plots with susceptible, Rag1 or pyramided Rag1+Rag2 varieties were all aggregated and did not differ among varieties in vegetative and reproductive growth stages. In addition, three-years of field experiments were used to access compatibility of aphid-resistant soybean with several non-target herbivores. Plant genotype affected seasonal abundance of bean leaf beetle (Cerotoma trifurcata Forster), potato leafhopper (Empoasca fabae Harris) and green cloverworm (Hypena scabra Fabricius). This thesis provides essential information for growers and scientists to incorporate these additional management tools into soybean aphid management programs.