Protecting Soybeans from Aphids, as Easy as (Rag) 1, 2, and 3

View the project final report

• 2016 annual report

Commodities

• Agronomic: soybeans

Practices

• Education and Training: demonstration, extension, on-farm/ranch research
• Pest Management: economic threshold, field monitoring/scouting, genetic resistance, integrated pest management

Advances in soybean breeding have produced varieties with single, double and triple gene combinations of soybean aphid host plant resistance. These naturally-occurring genes dramatically suppress aphid populations and will reduce the reliance of insecticides in soybean. Farmers using aphid-resistance genes will save on input costs and minimize negative effects to pollinators and beneficial insects associated with insecticides. 

To address both the short-term and long-term goals of soybean aphid management, our proposed project combines growth chambers, field cages and on-farm research in a collaboration that includes both soybean breeders, farmers, a non-profit organization and commodity organization. We propose a progressive and complementary process for screening new aphid-resistance genes against soybean aphid biotypes that have been discovered in the United States. 

Introduction:

Although soybean aphid can be patchy within fields and between growing seasons, it is considered the most economically important Iowa soybean insect pest since 2000. Soybean aphid can significantly reduce yield, and therefore regular scouting and timely foliar insecticides have been the primary way to protect yield. Advances in soybean breeding have produced varieties with single, double and triple gene combinations of host plant resistance for soybean aphid. These naturally-occurring genes dramatically suppress aphid populations and will reduce the reliance of insecticides in soybean. Farmers using aphid-resistance genes will save on input costs and minimize negative effects to pollinators and beneficial insects associated with insecticides. Documented pyrethroid resistance in some Midwestern states also stresses the importance of host plant resistance as a management tool.

1) We completed Objective 1 in 2016 (Year 1). Our results confirm that the Rag1+2+3 pyramid effectively manages all known soybean aphid biotypes. Our results indicate that Rag1+2+4 would be an effective management option for biotype-1, biotype-2, and biotype-3 soybean aphid, but had a negligible impact on biotype-4.

2) We complete our work on Objective 2 (Years 1-2). We have been using seed from increases developed by Brian Diers (University of Illinois), including access to several gene pyramids.

3) We completed Objective 3 (Years 1-3). Soybean aphid responded to resistant gene combinations in more realistic growing conditions similar to the laboratory testing. We worked with three commercial soybean farmers in northern Iowa and incorporated strip trials of host plant resistance each year. Aphid pressure was low, but overall, host plant resistance was an effective tool compared to susceptible soybean.

4) This project also had considerable extension efforts to communicate research findings to Iowa farmers. In 2018, we were a featured at a Practical Farmers of Iowa (PFI) field day in northern Iowa. We spoke about the use of host plant resistance to mitigate the impact of soybean aphid.

5) The funding to support this project helped train a graduate student, Erika Rodbell. On 23 April 2019, she defended her master’s thesis at Iowa State University and plans to continue work in sustainable agriculture.