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College of Food, Agricultural, and Environmental Sciences


Be Proactive When it Comes to Soybean Rust

June 10, 2004

WOOSTER, Ohio — For U.S. soybean growers, it's not a matter of if soybean rust will hit the states, just a matter of when. And the more educated growers are about the fungus, the better prepared they will be to manage it when that time does arrive.

Soybean rust is an aggressive fungus similar to the rust fungi that cause wheat leaf rust and corn leaf rust. The pathogen originated in China and has since made its way to Africa and South America, leaving yield losses and millions of dollars spent in fungicide treatments in its wake. It's had a home in Hawaii since 1994, but it has yet to be found on the North American continent. Nonetheless, Ohio State University plant pathologists and the Ohio Soybean Council want growers to be on top of the pathogen.

"Estimates from Brazil range from $750 million to $1 billion in additional fungicide costs each year to control soybean rust. In a $4 and $5-bushel marketplace, that would be devastating to our producers. With current $10 soybean prices we could manage it, but it's still a concern," said Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center. "Speculation on potential yield losses in the United States ranges from as high 50 percent or more. Rust will change the way we produce soybeans – when it gets here."

The American Soybean Association and the Ohio Soybean Council are sponsoring a Regional Soybean Rust Meeting on July 22 at the Der Dutchman Restaurant in Plain City, Ohio, to help soybean producers become better acquainted with soybean rust. Topics will include an overview of the disease (what it is, why should producers care about it and what are the government and industry doing to address it); what Ohio farmers need to know about soybean rust; application methods; fungicide availability and efficacy; and a Brazilian grower's perspective on his personal account of battling soybean rust. The meeting will run from 9:30 a.m. until 2 p.m.

"Our educational process has been in the works since January. The American Soybean Association started it with a conference in St. Louis and this summer took the show on the road for a series of seven meetings. We are hopeful soybean producers will put what they learned to work in preparation for soybean rust," said Susie Turner, executive director of the Ohio Soybean Council.

Dorrance stresses that growers should learn more about the pathogen, how it can be controlled and, most importantly, be proactive in scouting their fields.

"The reality is everybody should be scouting their fields. We've always been saying that," said Dorrance. "The main thing is that if they see something unusual on their plants, don't ignore it. Take a sample and send it away for analysis." To encourage growers to be more vigilant when it comes to diagnosing the disease, the Ohio Soybean Council, as part of the check-off program, has agreed to pay for samples to be tested at Ohio State's C. Wayne Ellett Plant and Pest Diagnostic Clinic.

"The Ohio Soybean Council and the soybean check-off want to help producers be preemptive in their approach to soybean rust," said Turner. "Paying close attention to their fields will go a long way in dealing with this disease and this is just one way the soybean check-off is paying off for producers."

Growers who wish to send plant material to the C. Wayne Ellett Plant and Pest Diagnostic Clinic for testing should adhere to the following guidelines:

• Place leaf, stem, or pod samples in a self-locking plastic bag and store under cool conditions.

• Samples that must be kept under ambient conditions should be sealed in a paper bag to prevent mold growth. Once they can be refrigerated the paper bag can be placed in a self-locking plastic bag.

• It would be helpful if leaves were placed between paper towels or pieces of paper to keep them flat. Care should be taken to ensure the outside of the bag is not contaminated by the sample.

• Record the collection information (date, exact location of the field and sample location within the field, county in which collected, host plant and collector's name and phone number) on a piece of paper included with the sample.

• Send samples to the following address: Soybean Rust-CWEPPDC, 110 Kottman Hall, 2021 Coffey Road, OSU, Columbus, OH 43210.

"We need to take steps to get this fungus diagnosed because it's a select agent, meaning that no one in the United States is supposed to have this. It also spreads quickly; it keeps depositing spores on plants before it can even be identified, so we want to treat it as quickly as possible and make the right fungicide recommendation depending on the stage of progress," said Dorrance.

When scouting fields, growers should concentrate on areas with low-lying water and in areas with heavy fog. The first signs of the disease are the development of small tiny brown or red brick spots on the top of the leaves. The spots are less than half the size of a leaf hair. On the underside of the leaf, the lesions break open to reveal cream-colored spores. The use of at least a 20X hand lenses is recommended to help spot the lesions and spores.

The process will continue as long as conditions are favorable for fungal development, causing premature defoliation leading to yield losses, fewer seeds per pod, decreased number of filled pods per plant and early maturity.

Currently, there are registered fungicides that work well against soybean rust and U.S. Environmental Protection Agency Section 18 Quarantine Exemption requests have been submitted by several states to expand the number of fungicides available. Ohio is one that has submitted a request.

"The catch on the Section 18s is that they do not go into effect until soybean rust is found in the continental U.S.," said Dorrance. In addition, the products are expensive; Ohio State researchers are currently studying ways to help producers save on application costs.

Ohio State plant pathologists, the Ohio Department of Agriculture, and the U.S. Department of Agriculture Plant Protection and Quarantine have drafted a management plan in the event soybean rust were to cross continental borders. Researchers speculate the mode of transmission to be via four specific routes: the Central American land bridge; hurricane winds via the Caribbean; spores on debris in shipments of seed or meal; or an act of bioterrorism with the final two being the least likely to occur.

For more information on soybean rust, contact Anne Dorrance at (330) 202-3560 or, Ohio State plant pathologist Pat Lipps at (330) 263-3843 or, or log on to Ohioline at and access Fact Sheet AC-0048-03. For more information on submitting samples to the C. Wayne Ellett Plant and Pest Diagnostic Clinic, contact Nancy Taylor at (614) 292-5006 or For more information on the Regional Soybean Rust Meeting contact Susie Turner at the Ohio Soybean Council at (614) 476-3100 or


Candace Pollock
Anne Dorrance, Susie Turner