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Research Highlights

Research Highlights
Georgia’s Sentinel Plots Catch Early Appearance of Asian Soybean Rust

Photo: Bob Kemerait

By Laura Temple

Sentinels stand guard and keep watch. A series of soybean plots and kudzu patches throughout Georgia do exactly that for soybean farmers. These plots and the team that monitors them keep watch for Asian soybean rust (ASR), an annual problem for soybean growers in the Southeast — the only region of the U.S. regularly impacted by this costly disease.

Following a mild winter in 2019-2020, ASR made its earliest appearance in Georgia since sentinel plot monitoring began. Sentinel plot monitoring, supported by the Georgia Agricultural Commodity Commission for Soybeans, alerted southeastern soybean farmers and provided information to help them make treatment decisions.

“Our plots give growers a heads up about where and when ASR is in Georgia,” explains Bob Kemerait, a plant pathology professor and Extension specialist with the University of Georgia. “This information helps them determine if a well-timed fungicide application is needed or not.”

Kemerait says research shows that fungicides applied based on early warnings may protect soybean yields by 25 bu/A or more. Some years, fungicide applications make sense, while other years, fungicides may not be necessary.

Georgia’s sentinel plots include patches of kudzu, an overwintering host for ASR, scattered throughout the state. Also, soybean plots containing varieties of three different maturity groups are planted early at Georgia’s experiment stations as sentinel plots. All plots are monitored weekly from April through September. Leaves collected from the kudzu and soybeans come into a lab where they are examined closely under a microscope.

Photo: Bob Kemerait

“We are looking to find that needle in a haystack” Kemerait says. “We want to find the one pustule of rust from a sample of 50 leaves that shows the disease has appeared.”

Once ASR is detected, information about what county it was found in and the potential for its spread is shared with county Extension agents, added to the ASR map and posted on Twitter. Kemerait says soybean farmers in neighboring states also benefit from watching Georgia’s monitoring to know when ASR is moving their direction.

“The process follows a plan that was implemented when ASR showed up in the U.S., and it’s been so effective we are still using it 16 years later,” he adds. “Our soybean growers invest in this program every year so they are not surprised by this and other diseases.”

In addition to ASR, Kemerait notes that sentinel plots are monitored for other soybean diseases, including Cercospora leaf blight, frogeye leaf spot, anthracnose and more.

“We appreciate soybean grower trust in Extension to provide this information every year,” he continues. “This investment pays off for the growers by allowing them to make timely fungicide applications as appropriate, or to delay applications until needed each year, based on what we find in the sentinel plots.”

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.