Released September 5, 2008

LITTLE ROCK, Ark. - So far Arkansas is free of Asian soybean rust, but that could change as the remnants of Hurricane Gustav threaten to spread the disease here.

The rain also will delay the harvest of crops until next week for many farmers. As of Wednesday afternoon, the storm had drenched Pine Bluff with 3.4 inches of rain, Monticello with 5 inches and Hot Springs with 8 inches in a 24-hour period, according to the National Weather Service.

"Corn has been ready for harvest two or three weeks, and the issue is whether the stalks can survive the wind and rain," said Jason Kelley, extension wheat and feed grains specialist with the University of Arkansas Division of Agriculture.

But soybean and disease experts are more concerned with Asian soybean rust. The disease has remained active in Texas and Louisiana for several weeks, and has spread from Florida into Georgia, according to Scott Monfort, assistant professor and extension plant pathologist.

"However, predicted rain moving in from the south because of Hurricane Gustav could change the current status of soybean rust over the next couple of weeks," Montfort said. Because of this, Arkansas and most of the Mississippi Delta region will remain at risk for the development and spread of soybean rust until late September.

Monfort said county agents and volunteers are continuing to scout kudzu patches, soybean sentinel plots and soybean fields throughout the state. Kudzu is a host crop for the disease, so kudzu patches are watched closely.

"An estimated 60 percent of the nearly 3 million-acre soybean crop is in the reproductive stage," he said. "With this in mind, county agents need to continue monitoring soybean sentinel plots and/or kudzu patches and continue sending suspicious samples to the diagnostic lab at Lonoke."

Monfort encouraged consultants and growers to also send suspicious kudzu and/or soybean samples (at least 100 leaves) during the season if they think they have soybean rust.

Asian soybean rust symptoms are most commonly found on the underside of the lower leaves, starting around the flowering stage. Initial symptoms of infection are difficult to detect because the lesions are small. It’s always detected first in the lower plant canopy.

The first symptoms of soybean rust are small brown to reddish-brown spots on the upper leaf surface. Hold leaves up to the sun, Monfort suggested. This will help you see any tiny brown spots starting to form.

Asian soybean rust fungus was first identified in Japan in 1902. It was discovered in South America in 2000, and a hurricane in the Gulf of Mexico later carried spores into the southern United States.

Under the right conditions, the disease can cause premature defoliation and reduce soybean yields by as much as 80 percent. The severity can double every two to nine days, depending on environmental conditions.

Soybean rust tends to overwinter in the southern costal regions. It has been estimated that the disease could cost U.S. soybean producers $240 million to $2 billion annually.

Monfort said an updated list of fungicides to treat soybean rust is available from county agents with the Cooperative Extension Service. He urged growers to carefully read the product labels before using the fungicides.

"Any suspicious leaves (soybean and/or kudzu) can be sent to the Lonoke Diagnostic Lab. The Soybean Rust Hotline is continually updated with information about the latest rust finds that number is 1-866-641-1847," he said.

If you have any questions or concerns please contact your county agent, Scott Monfort (870-659-0648), Jeremy Ross (501-944-0621) or Amy Carroll (870-258-2509).

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http://www.uaex.edu/news/september2008/0905soybeanrust.htm

Contact: Lamar James, (501) 671-2187, ljames@uaex.edu