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College of Food, Agricultural, and Environmental Sciences


Soybean Rust Risk in Ohio Low

July 27, 2009

WOOSTER, Ohio – The risk for soybean rust on Ohio's soybean crop is low and, once again, the crop may escape the disease.

Anne Dorrance, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, said that hot temperatures throughout the Deep South, coupled with the lack of any major Atlantic storms, is keeping the disease at bay across such states as Texas, Louisiana, Alabama, Florida and Georgia.

"At this point it doesn't look like anything is going to happen on the soybean rust front over the next few weeks during the critical time of flowering and pod setting," said Dorrance, who also holds an Ohio State University Extension appointment.

Dorrance and her colleagues are actively monitoring for the presence of soybean rust spores via spore traps set up at various locations across the state, in addition to leaves from Ohio's 10 sentinel plots, and through laboratory research.

"From now until mid-August we'll be collecting leaves and looking under the microscope every week to verify that rust has not been found," said Dorrance. "If rust comes in at the end of August, it's not going to have a yield impact because it's just coming in to the state too late," said Dorrance. "There really is only four to five weeks now that I lose sleep over monitoring where soybean rust is."

Since its discovery in the United States in 2004, researchers across the U.S. have learned quite a bit about soybean rust:

• The disease is manageable.

• Kudzu is an overwintering host for the disease, but not all kudzu species are susceptible.

• The amount of inoculum is greatly reduced over winter.

• Several effective fungicides have been identified for soybean rust control.

• Soybean rust is UV light sensitive. Sunlight can actually kill spores.

• The development and spread of the disease is highly weather dependent.

• The disease does not appear to jump onto soybeans from other hosts until after flowering.

For the latest information on soybean rust development across the United States, log on the U.S. Department of Agriculture's Integrated Pest Management-Pest Information Platform for Extension and Education Web site at

The "Using Foliar Fungicides to Manage Soybean Rust" manual has also been updated. To purchase a copy, log on to

Candace Pollock
Anne Dorrance