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Precision Farming Targets Major Threat to Soybean Crops

Flying drone over a field while the sun sets

Over the last 15 years, farmers across the U.S. have faced a daunting challenge. The soybean aphid, an invasive species first reported in the U.S. in 2000, has flourished on farms. These tiny yellow insects can destroy up to 40 percent of a soybean field when left unchecked. This is bad news for Minnesota, where soybeans are the top export crop and farmers produce 3 billion bushels of beans a year, according to the Minnesota Soybean Research and Promotion Council.

A team of University of Minnesota researchers is working to give farmers better tools and techniques to protect their crops from pests like the soybean aphid. Using high-tech robotics and sensors and computer modeling software, the team aims to develop faster and more efficient methods of monitoring crops that help farmers make informed decisions on exactly when and where to apply pesticides. The project is part of the state-funded MnDRIVE Transdisciplinary Research Program, where researchers from different departments work beyond the limits of their disciplines to address complex challenges.

Demoz Gebre-Egziabher, Ph.D., lead principal investigator on the project and associate professor of aerospace engineering and mechanics with the U’s College of Science and Engineering, said greater precision when spraying for pests is crucial for farmers. Applying pesticide too soon could end up killing the aphids’ natural predators, which then allows the aphids to grow out of control. Waiting too long, on the other hand, lets the aphids reproduce freely and take over the crop.

“Optimizing pesticide application is a complex science,” Gebre-Egziabher said. “We’re developing a cost-effective way for farmers to collect data from the field, process it and come up with an action plan for how to curb their crop loss without spending too much on treatments.”

Soybean aphids are a problem because they slowly drain soybean crops of their sap — the fluid that circulates nutrients through the plant’s vascular system. In large enough numbers, the insects weaken the plant’s growth and harm its ability to produce the soybean pods that farmers harvest. In extreme cases, the aphids can even kill the plant.

In the early 2000s, David Ragsdale, Ph.D., a U of M entomology professor now at Texas A&M University, led a large-scale collaborative research effort across the Upper Midwest to learn how to handle the new aphid threat. He and his colleagues established a threshold that would allow farmers to balance the cost of aphid control with the cost of crop loss: apply pesticide when 80 percent of a soybean crop has aphid infestations and more than 250 aphids are on each plant.

The problem, however, is that determining how many aphids are on a soybean crop is a slow and time-consuming process. Once a week, farmers or the crop scouts they hire must physically go to different parts of the field, examine the crop and count the number of aphids one by one.

To improve the scouting process, Gebre-Egziabher and his team are taking it to the skies. They have equipped small, remote-controlled planes, known as uninhabited aerial vehicles, or UAVs, with specific types of sensors that can detect near-infrared light, which is invisible to the naked eye. Plants reflect this wavelength of light in different amounts based on the quantity of chlorophyll in their leaves. When an aphid infestation stresses the plant, it produces less chlorophyll, giving the UAVs a way to detect something is wrong from high overhead. Using these tools, the researchers can monitor the fields in a more comprehensive way.

“We’re looking to assess the level of stress that a plant is under and directly associate that with aphid population levels,” said Ian MacRae, Ph.D., professor of entomology with the U’s College of Food, Agricultural and Natural Resource Sciences (CFANS) whose office is located at the Northwest Research and Outreach Center, near the U’s Crookston campus. “This is going to change the landscape in crop production.”

After gathering information from above, experts at the U plan to analyze it to aid farmers in deciding when and where to apply pesticides to their crops. Ultimately, the researchers hope to create a software modeling program that will perform the analysis automatically and provide farmers an on-location field report through a laptop computer.

A More Precise Approach to Agriculture

From the UAV technology to the aphid populations, it takes a host of experts from across academic disciplines to develop a solution to a complex problem like invasive soybean aphids. Through their collaboration, Gebre-Egziabher said, the researchers found working together begins with understanding one another’s fields of expertise and where they intersect.

“Coming from different academic backgrounds encouraged us to consider the problem of soybean aphid infestations through many different viewpoints, from the technological to the economic,” he said. “This collaboration allows us to approach and study the issue in a more comprehensive way, and will ultimately help us arrive at a more robust solution.”

Right now, Gebre-Egziabher is continuing to improve the UAV technology to ensure its safety and reliability, aided by three colleagues from the College of Science and Engineering: Peter Seiler, Ph.D., assistant professor of aerospace engineering; Brian Taylor, director of the U’s Uninhabited Aerial Vehicle Lab; and John Weyrauch, industrial professor of design. These aerospace experts are also studying the regulatory environment for UAVs to identify any barriers that might make it more difficult for farmers to use this emerging technology. The researchers have also helped provide information to Minnesota legislators on how the aircraft work to better inform future policy decisions. For the time being, they have obtained authorization to conduct test flights at several sites around the state, including the U of M Outreach Research and Education (UMore) Park in Rosemount, Minn.

Meanwhile, MacRae is working with Robert Koch, Ph.D., assistant professor of entomology in CFANS, to pinpoint the exact wavelengths of light that will link what sensors detect from above to severe aphid infestations below. Part of the challenge with their efforts includes separating aphid-related stress from similar near-infrared light soybean plants may emit as a result of other afflictions or diseases.

Terrance Hurley, Ph.D., professor of applied economics with the College of Food, Agricultural and Natural Resource Sciences, will assess the economic impact of monitoring soybean aphids using the new technology. Through measurements of the amount of pesticide used, the size of the soybean yield and numerous other factors, Hurley aims to understand the economic trade-off between traditional scouting and UAV-based remote sensing.

While the team’s focus is on soybean aphids, the technology and methods they are developing have enormous potential to be adapted for other uses. MacRae hopes to see the technology expand to serve a wider variety of agricultural applications, from watering crops to monitoring plant diseases.

“It has been a really valuable collaboration, and an enormously productive one,” he said.

This project is supported by MnDRIVE, a landmark partnership between the university and the state of Minnesota that aligns areas of university strength with the state’s key and emerging industries to advance new discoveries that address grand challenges.

Kevin Coss

Kevin Coss

Kevin is a writer and public relations associate with the Office of the Vice President for Research.

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