A survey of soybean farmers about integrated pest management practices for soybean aphid (Aphis glycines) finds misunderstandings about terms such as “economic threshold” and “economic injury level.” The results suggest that improved and well-tailored communication efforts could improve adoption of IPM principles. (Photo by Bruce Potter)

By Natalie Hoidal

Natalie Hoidal

Economic thresholds are a cornerstone of integrated pest management, but they are not always widely adopted by growers and agricultural professionals. In the context of soybean aphid, there is an economic threshold in the Midwest that is well supported by research. Soybean aphid (Aphis glycines) was first detected in 2000 in North America, and large outbreaks have since occurred throughout the Midwest, resulting in yield reductions of up to 40 percent. While growers have relied primarily on pyrethroid insecticides for management, researchers have begun to document insecticide-resistant aphids across Minnesota.

In a new paper in the open-access Journal of Integrated Pest Management, my co-author Robert Koch, Ph.D., and I review the results of a survey we conducted with 500-plus farmers and agricultural professionals. The goal of the study was to better understand how these different stakeholders perceive and use the economic threshold for soybean aphid, and how educational programs can better target the needs and barriers faced by specific stakeholder groups to improve adoption. While specific to soybean aphids, our findings shed light on how improved communication efforts that are tailored to the specific needs of various stakeholders can improve adoption of integrated pest management (IPM) principles.

Barriers to Using Thresholds

Overall, we found significant differences between farmers, sales agronomists, consultants, pesticide applicators, and co-op managers in their perceptions and practices related to the soybean aphid threshold. Farmers and sales agronomists were more likely than the other groups to treat or recommend treatment of fields below the economic threshold of 250 aphids per plant. Some of the most common barriers to trusting the economic threshold included worries about how soybean aphid pressure might interact with other stressors, as well as misunderstanding the difference between the economic thresholds and economic injury level. In addition, many farmers and agricultural professionals expressed worry that by the time aphids reached the economic threshold, there would not be sufficient time for them to get to all of the fields requiring treatment to prevent significant yield loss.

In a survey of soybean farmers about integrated pest management practices for soybean aphid (Aphis glycines), some of the most common barriers to trusting the economic threshold included worries about how soybean aphid pressure might interact with other stressors, as well as misunderstanding the difference between the economic thresholds and economic injury level. (Photo by Robert Koch, Ph.D.)

Tailoring Educational Outreach

Each group we surveyed had different educational needs. Farmers expressed worry about cumulative effects of other stressors in addition to stress from soybean aphids, and educational outreach should address this. Sales agronomists, farmers, and pesticide applicators were more likely than other groups to report seeing yield impacts if they waited to spray, so sharing data from trials used to develop and continually validate the economic threshold may be important for these stakeholders. Most consultants trusted the threshold, but they were also the most likely group to recommend what their customers asked for. As such, education to consultants should focus more on developing skills to provide research-based recommendations to customers.

Addressing Misconceptions and Barriers

IPM programs should focus on more clearly communicating the process by which economic thresholds are developed, and how these thresholds account for additional stressors beyond the insect pest upon which the threshold is based. We were surprised to see misunderstandings about the definitions of “economic threshold” and “economic injury level.” Therefore, continuing to reinforce the basics of IPM when presenting new concepts or research is likely to improve stakeholder understanding and adoption. Finally, by investing time in understanding the unique barriers that practitioners face in IPM adoption, educators can better empathize with their audience and tailor their messages to stakeholders, which is key to building trust.

Natalie Hoidal is an assistant extension professor at the University of Minnesota’s Center for Agriculture, Food, and Natural Resources in Farmington, Minnesota. Email: hoida016@umn.edu.