Soybean rust found in Alabama sentinel plot

Soybean rust, a fungal disease that can decimate yields, has been found in a soybean sentinel plot in Washington County according to Ed Sikora, a plant pathologist with the Alabama Cooperative Extension System.

More recently, it was detected on kudzu in Bay Minette in Baldwin County.

"This is the earliest soybean rust has ever been found on soybeans in Alabama," he says. "Previously, the earliest we have seen rust on soybeans was during the last week of June in three of the past four years and not until late July in 2008.

"This indicates that rust could be a more significant problem this year depending on how weather conditions develop over the next few months."

The mild winter allowed soybean rust to over-winter on kudzu at relatively low levels in Mobile County and in a few parishes and counties in Louisiana, Georgia and Florida.

"This, along with the relatively cool, wet spring has allowed the disease to be more active than in recent years."

Sikora adds that tropical storms moving out of the Gulf of Mexico could speed the spread of the disease because spores are dispersed by winds.

"A storm pushing out of the gulf could pick up rust spores from along the Gulf Coast and spread those spores any number of miles," he says.

Sikora adds that while reports from other countries suggest the disease can spread 100 miles a day, he has not documented that type of rapid spread in Alabama.

"This can be a devastating plant disease. Yield losses of 40 to 50 percent are possible in soybeans when the disease invades a field early in its development and no fungicides are used to prevent spread of the pathogen."

The extent of yield losses will depend on the time and severity of infection. Under favorable conditions, rust can cause premature defoliation of infected plants. Heavily infected plants also have fewer pods and lighter seeds, which can lead to significantly less marketable yields.

Current estimates for soybean plantings in Alabama stand at 400,000 acres with significantly more acres than cotton, corn or peanuts.

"Farmers cannot afford to lose large portions of their crop to disease."

Sikora's advice to soybean farmers is to monitor the spread of the disease and be prepared to apply a fungicide if disease spreads to a nearby county.

"We suggest growers consider applying a fungicide when the risk of rust is high and their crop is between full bloom and podfill. Currently, we are suggesting that soybean growers in Baldwin, Mobile and Washington counties with a crop that has pods beginning to develop at one of the uppermost nodes strongly consider applying a fungicide at this time. We will continue to monitor the situation in south Alabama closely in the coming weeks."

For more information on soybean rust, view the United States Department of Agriculture rust information Web site at When viewing the national map, click on Alabama to read Sikora's weekly commentary and recommended management practices for the state.

TAGS: Soybeans
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