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Soybean aphid control gets update

Farming needs new ways and better management to fight an old pest.

Kevin Schulz, Editor

April 5, 2023

3 Min Read
soybean plant leaf covered with aphids
TRIGGER POINT: Scouting fields for soybean aphids is important to determine when insecticide application is necessary, keeping in mind the threshold of 250 aphids per soybean plant. Farm Progress

Soybean aphids are nothing new, but farmers need to look at new ways to battle the veteran pest.

An organophosphate, chlorpyrifos, that had been used is no longer available in the farmer’s toolbox. As Robert Koch, University of Minnesota associate professor and Extension entomologist, says, “The tolerances for that chemical were revoked so we cannot use it for management of soybean pests anymore.”

Adding to that aphid conundrum is that two neonicotinoid insecticides imidacloprid and clothianidin have been added to a “Surface Water Pesticides of Concern” list, as they have been detected in Minnesota rivers and streams above toxicity concentrations harmful to aquatic organisms. Koch says this has prompted the development of best management practices “that relate to the seed-applied formulations and foliar formulations of these two neonicotinoid insecticides.”

Best management practices aim to provide guidance on how to better follow label instructions on the use of these insecticides, and to implement an Integrated Pest Management Program, with the ultimate goal of reducing the number of detections of these insecticides in surface water and the magnitude of those detections. “These are voluntary BMPs,” Koch says. “Again, the goal is to decrease the contamination of the surface waters so that, hopefully, the state won’t have to increase any formal regulations against these pesticides.”

In addition to getting farmers to stick to the label for application, this also means the options in a producer’s toolbox are getting sparse.

On top of a thinning toolbox repertoire, Koch says resistance to Group 3 pyrethroid insecticides makes choices even fewer. He points out that new insecticides such as Sefina (Group 9), Transform and Sivanto (both Group 4) showed performance rivaling old standby Lorsban. “They are effective, even when we have pyrethroid resistance potentially in the field,” he says, “so because of that, I think we really need to keep insecticide resistance management in mind — so we can preserve these remaining effective insecticides for as long as we can.”

Manage insecticide resistance

Koch says the first step in managing resistance is spraying only when needed — and that means regular scouting of fields, and not just the view from the pickup window when driving by on the road. Using the economic threshold of 250 aphids per plant is recommended as the trigger point to spray, but Koch also suggests paying attention to spray rates, volumes and proper nozzles “to ensure you’re getting good, effective concentration of insecticide on the plants.”

He adds that gone are the days of spraying and forgetting. “Go back in three to five days after spraying, to make sure that that insecticide worked, and then if we have a failure and need to respray or retreat that field, alternating to a different insecticide group. So pay attention to those group numbers on the insecticide labels.”

He adds that these newer insecticides that, while toxic to the aphids, are “much less toxic or more gentle on the good insects, like the predators or parasitic wasps which can provide natural control of the pest population.”

Koch’s presentation was part of a webinar in the University of Minnesota’s Strategic Farming series.

About the Author(s)

Kevin Schulz

Editor, The Farmer

Kevin Schulz joined The Farmer as editor in January of 2023, after spending two years as senior staff writer for Dakota Farmer and Nebraska Farmer magazines. Prior to joining these two magazines, he spent six years in a similar capacity with National Hog Farmer. Prior to joining National Hog Farmer, Schulz spent a long career as the editor of The Land magazine, an agricultural-rural life publication based in Mankato, Minn.

During his tenure at The Land, the publication grew from covering 55 Minnesota counties to encompassing the entire state, as well as 30 counties in northern Iowa. Covering all facets of Minnesota and Iowa agriculture, Schulz was able to stay close to his roots as a southern Minnesota farm boy raised on a corn, soybean and hog finishing farm.

One particular area where he stayed close to his roots is working with the FFA organization.

Covering the FFA programs stayed near and dear to his heart, and he has been recognized for such coverage over the years. He has received the Minnesota FFA Communicator of the Year award, was honored with the Minnesota Honorary FFA Degree in 2014 and inducted into the Minnesota FFA Hall of Fame in 2018.

Schulz attended South Dakota State University, majoring in agricultural journalism. He was also a member of Alpha Gamma Rho fraternity and now belongs to its alumni organization.

His family continues to live on a southern Minnesota farm near where he grew up. He and his wife, Carol, have raised two daughters: Kristi, a 2014 University of Minnesota graduate who is married to Eric Van Otterloo and teaches at Mankato (Minn.) East High School, and Haley, a 2018 graduate of University of Wisconsin-River Falls. She is married to John Peake and teaches in Hayward, Wis. 

When not covering the agriculture industry on behalf of The Farmer's readers, Schulz enjoys spending time traveling with family, making it a quest to reach all 50 states — 47 so far — and three countries. He also enjoys reading, music, photography, playing basketball, and enjoying nature and campfires with friends and family.

[email protected]

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