Research Highlights

Research Highlights
Sentinel Plots Keep Watch for Diseases

Foliar symptoms of Cercospora leaf blight.

By Laura Temple

Since 2005, a series of soybean sentinel plots across Georgia have been serving as lookouts for the appearance of Asian soybean rust, or ASR. The disease threatens soybeans annually in Georgia and other Gulf Coast states — including Alabama, Florida, Louisiana and Mississippi.

“The sentinel plot program was started to help soybean farmers manage rust, but their value has been extended to other diseases and crops,” explains Bob Kemerait, a plant pathology professor and extension specialist with the University of Georgia. 

He relies on consistent soy checkoff funding from the Georgia Agricultural Commodity Commission for Soybeans to maintain and monitor the soybean sentinel plots.

“Georgia soybean growers recognize the value of these plots in helping them protect yield and save fungicide application costs,” he says. “To date, we work together to continue moving forward with these plots. I appreciate how they invest in this because they believe it works.”

In addition to obtaining physical evidence and data from the sentinel plots, Kemerait receives disease reports from crop consultants, farmers and industry agronomists from Georgia and surrounding states. He considers this an unexpected benefit of the program.

Asian soybean rust can severely damage soybean plants. Photo: Bob Kemerait

“Because of our sentinel plots, they understand we want to know about diseases,” he says. “We get more information, which allows us to share even better recommendations for disease control.”

Monitoring Key Diseases

In addition to watching for ASR, the sentinel plots monitor development or movement of other major soybean diseases. 

Cercospora leaf blight is a disease relatively new to our monitoring effort,” Kemerait says. “As we expand our monitoring, it’s proof that we are watching both for what we know and what we didn’t know.”

He describes Cercospora leaf blight as a greater chronic annual threat than ASR. It overwinters in crop debris, and its symptoms can be easily confused with other problems in the field. Because it can be misidentified or missed, the sentinel plots bring crucial attention to it.

In northern Georgia, frogeye leaf spot can become a problem nearly every year because it can infect seeds or survive in crop debris. The sentinel plots remind growers to watch for this disease. Monitoring also draws attention to anthracnose and target spot. 

Farmers benefit from following the spray recommendations that come out of the sentinel plots and additional disease monitoring information. For example, ASR appeared early in 2022, but it was slow to develop. It finally reached a point when Kemerait recommended treating it with fungicide. 

“Though it was late in the season, fields that weren’t treated sustained significant yield loss,” he says. 

Based on the learnings and success from the soybean sentinel plots, Kemerait has developed similar systems for other crops. For example, through corn sentinel plots, he and his team monitor for southern rust, and now tar spot, which has moved into the region. Following the example of the Georgia Soybean Commission, the Georgia Commodity Commission for Corn funds these plots.

“Farmers invest in these programs to be proactive in protecting yield and profits, and they see the benefits,” he says. 

When disease pressure does not warrant fungicide applications, he estimates that farmers save $10 to $25 per acre in input costs. However, ASR alone can cost 25 to 40 bushels per acre in yield, so timely applications as recommended by the sentinel plots protect yield and profitability.

Bob Kemerait profile

Published: Mar 13, 2023

The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.