Soybean production in Minnesota continues to be threatened by insect pests, most notably the soybean gall midge (Resseliella maxima) and the soybean aphid (Aphis glycines). This project addresses a priority item listed under the category of Soybean Pest Management in the FY2025 request for proposals: ”Soybean farmers need continued research into cultural, chemical and biological control mechanisms for management of soybean insects including, but not limited to, soybean aphid, Japanese beetle and soybean gall midge.”
Soybean gall midge is a new destructive pest of soybean in the Midwest. Soybean gall midge larvae feed inside the stems of soybean plants near the soil surface (McMechan et al. 2021). Infestations cause wilting, lodging and death of soybean plants, and have resulted in significant yield reductions (McMechan et al. 2021). This pest has been reported from seven Midwest states and its known geographic range in Minnesota continues to expand with reports from 30 counties extending from the southwest corner of the state to the Twin Cities area (soybeangallmidge.org). Management of soybean gall midge with insecticides has shown only limited effectiveness to date, so additional management strategies are needed. For many crop production systems, host plant resistance (i.e., the use of pest-resistant crops) is the cornerstone to integrated pest management programs. Soybean varieties resistant to soybean gall midge are not available, but recent multistate research has identified several soybean genotypes with potential resistance to soybean gall midge. Further research is urgently needed to verify this resistance under controlled conditions and to characterize the type of resistance against this pest (i.e., effects on pest biology [antibiosis] versus effects on pest behavior [antixenosis]). Our team has the only known laboratory colony of soybean gall midge in the world, and we will leverage this important resource to produce the data necessary for soybean breeders to determine if and how to incorporate soybean gall midge resistance into their breeding programs. Dr. Justin McMechan from the University of Nebraska-Lincoln is thrilled to collaborate with us in this project and will provide seeds of the soybean genotypes with potential resistance to soybean gall midge. We will also test new technology called the “Insect Eavesdropper” (https://www.insecteavesdropper.com/), which is a highly sensitive sound recording device that can be connected to plants to hear the sounds of insects feeding on (or in) plants. Because soybean gall midge larvae feed out of sight within soybean stems, this technology could provide a more efficient means for assessing the level of infestation of plants (i.e., high-throughput phenotyping). Dr. Emily Bick from the University of Wisconsin is developing the Eavesdropper technology and is excited to collaborate with us on this project. The research proposed here has a high probability for success, because of existing field data indicating potential resistance in some soybean genotypes, our extensive experience researching the biology of soybean gall midge, and our experience screening for and characterizing soybean resistance to other pests.
The soybean aphid remains the most damaging insect pest of Minnesota soybean. Infestations by this pest can reduce soybean yields by 40% (Ragsdale et al. 2011). This insect was initially managed effectively with scouting and threshold-based applications of foliar insecticides, mainly pyrethroids and organophosphates. However, in 2015, we documented the first cases of pyrethroid resistance in soybean aphid (Hanson et al. 2017), and have since documented resistance of soybean aphid to pyrethroids across Minnesota and into neighboring states and provinces (Menger et al. 2020). This resistance has resulted in severe reductions in the efficacy of pyrethroid insecticides in the field (Menger et al. 2022). Despite the resistance to pyrethroids, insecticide products containing formulated mixtures of a pyrethroid and a neonicotinoid (e.g., Endigo, Leverage 360, etc.) remained commonly used and were effective against resistant and susceptible soybean aphid populations. However, we have documented decreasing performance of these mixtures (da Silva Queiroz et al. 2019, Aita et al. 2019) and, in 2024, we documented an extreme failure of Leverage 360, where plots treated with this product had nearly three times more aphids per plant than untreated plots at 15 days after treatment. Fortunately, some newer products known to be effective against soybean aphids and less toxic to natural enemies (predators and parasitic wasps) are available for soybean aphid control, such as sulfoxaflor (Transform), afidopyropen (Sefina) and flupyradifurone (Sivanto Prime). Chemical control of soybean aphid has become greatly complicated by insecticide resistance, regulation, and availability of new products with which many growers have limited experience. Therefore, the work proposed here will establish a standardized comparison of many of the groups and formulations of insecticides available for soybean aphid control. Growers will be provided timely data on the efficacy of the products against soybean aphid and other pests that may be abundant, as well as impacts of the products to the natural enemies that provide natural control of soybean aphid. By repeating this research in future years, we will be able to detect changes in the efficacy of these insecticides, which will provide a means for detecting and quantifying new cases of insecticide resistance. The research proposed here has a high probability for success, because of our extensive experience researching chemical control and monitoring of insecticide resistance of soybean pests, and the methods proposed here have been previously used in our laboratory to evaluate the toxicity of pesticides to multiple pests of soybean, including soybean aphid (da Silva Queiroz et al. 2019, Aita et al. 2019).