SDSU gene research: Evaluating efforts to reduce soybean aphids

Farm Forum

Kelley Tilmon, an associate professor of entomology in SDSU’s Plant Science Department, spent part of 2013 field season evaluating soybean genes that confer resistance to the soybean aphid, a major insect pest of soybeans.

Tilmon explains that different genes have been discovered that make soybean plants at least partially resistant to the aphids, and plant breeders have been working to breed them into varieties for commercial production. Tilmon’s research efforts are to identify how these genes perform in the field.

She explains, “We are involved in testing experimental aphid-resistant plant lines and how they actually perform in the field with regard to reduction in insect pressure. The study we conducted in 2013 looked at two different genes (Rag1 and Rag2), how they performed alone, and how they performed when ‘pyramided’ together. We also looked at how aphid populations fared on these plants containing these genes with and without the use of insecticidal seed treatments applied at planting because this is a common agricultural practice now.”

She adds, “Resistant varieties are an important part of insect pest management because they provide us with a way to decrease insect pest pressure without relying exclusively on pesticides. This is good for farmers because it can reduce their input costs and the time they spend on pest management, and it’s good for the environment because it helps lessen pesticide use.”

Another research project of Tilmon’s looked at how different pesticide seed treatments affect soybean aphid populations in the field, with a particular focus on the cost/benefit ratio of those seed treatments.

Tilmon says they are evaluating how often and to what degree seed treatments reduce aphid populations. As well, they are asking: what is the economic benefit of the reduction compared to the cost of the product, and how does that compare to the cost of other pest management tactics?

“This is important because producers often invest in seed treatments for insect control, but independent, university research on the true cost/benefit ratio of these products still needs to be conducted to provide producers with unbiased information on what they can expect from these products,” Tilmon says.

In a third project, Tilmon is also researching soybean aphid biotypes that have overcome resistant soybean varieties. She explains, “For every plant defense there is usually a counter-attack from pests, and plant resistance genes are no exception. Several soybean aphid genotypes have been found which do much better on resistant varieties, which reduces the effectiveness of the plant resistance. We are monitoring for such biotypes in South Dakota to see which ones we have and how common they are.”

Year-round Tilmon is also involved in directing a $2.1 million multistate research and extension project funded by the North Central Soybean Research Program to study soybean aphid biology and management. She reports that this project involves 22 researchers in 12 states and is a large coordinated effort to provide pest management solutions to soybean producers throughout the region.

Tilmon also credits the South Dakota Soybean Research and Promotion Council and the North Central Soybean Research Program, with helping make much of the research and education efforts SDSU is involved with possible through the farmer-generated checkoff dollars to promote research and development for their crops.

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