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College of Food, Agricultural, and Environmental Sciences


Frogeye, Not Rust, Found in Ohio Soybean Sentinel Plots

June 25, 2007

WOOSTER, Ohio -- Ohio State University's soybean sentinel plot program, established in 2005 to track soybean rust (still a no-show in Ohio), is fulfilling its purpose as the first line of defense against more immediate, threatening diseases. One of those is frogeye leaf spot.


The foliar disease, rare in Ohio, was recently identified at one of the 45 sentinel plot locations.

"This is one of the clear benefits of this sentinel plot program. We can find and detect a disease long before controls need to be implemented," said Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center. Dorrance, who also holds an Ohio State University Extension appointment, was one of several university researchers instrumental in establishing the national program of sentinel plots.

The early detection of frogeye is helpful for growers who can now begin scouting their fields for any potential problems.

Although uncommon in Ohio, the disease has been showing up more frequently the past several seasons, and can greatly impact susceptible soybean varieties. Last year was the first time growers suffered economic losses to frogeye -- anywhere from 10 percent to 30 percent yield losses on 300,000 acres.

"The good news is we scored varieties in the Soybean Variety Performance Trials last year and over 90 percent of the entries had high levels of resistance," said Dorrance. "We don't expect a similar economic problem this year, but it is good to monitor the situation."

The frogeye pathogen survives in crop residue and makes its appearance in mid to late July, affecting leaves and sometimes spreading to stems and pods. Frogeye lesions are distinct from other soybean foliar diseases in that they have a gray-silver center surrounded by a cranberry-red border.

Growers can manage frogeye by:

• Practicing tillage to bury crop residue and reduce the amount of disease inoculum.

• Practicing crop rotation.

• Planting resistant varieties.

"Conditions for the next few weeks are predicted to be hot and dry. Frogeye requires moisture and tends to infect young new leaves as opposed to older leaves," said Dorrance. "For the next few weeks we will be surveying the state to determine how widespread this is and if fungicides will be needed."

For future updates on frogeye and other soybean foliar diseases, log on to Ohio State University's Agronomic Crops Team Web site at


Candace Pollock
Anne Dorrance