Asian Soybean Rust Shows Up Late Again This Year In Louisiana

Raymond Schneider, Chaney, John A.  |  11/11/2005 3:19:51 AM

LSU AgCenter researcher Dr. Ray Schneider, at left, recently (Nov. 9) helped a group of crop consultants learn how to detect Asian soybean rust. The disease showed up on the AgCenter’s Ben Hur Farm in Baton Rouge late in the season again this year – as it did last year when Schneider discovered the first appearance of the problem in a U.S. field.

News Release Distributed 11/10/05

Almost a year after Dr. Ray Schneider discovered the country’s first known occurrence of Asian soybean rust, LSU AgCenter researchers identified the disease again in nearly the same place.

The November discovery on an LSU AgCenter farm was the first time the disease was identified in Louisiana in 2005, said Schneider, an LSU AgCenter plant pathologist.

With Louisiana’s soybean crop nearly 95 percent harvested, farmers are urged to continue harvesting their crops, because there should be little to no spread of the spores to the remaining cropland, said Dr. David Lanclos, LSU AgCenter soybean specialist.

"Asian soybean rust can be devastating to the yield of soybeans when the conditions are appropriate – especially when the humidity is high and nighttime temperatures are between 75 and 85 degrees," Lanclos said.

After first being discovered in Louisiana in November 2004, Asian soybean rust was found in other locations late in that season. Then it reappeared for the first time in 2005 on kudzu in central Florida in February.

"It apparently spread from there north," Schneider said. "It was first found in kudzu, then in volunteer soybeans and finally in commercial soybeans in early July."

The plant pathologist said the disease spread from the Florida panhandle into Georgia, Alabama and Mississippi, where it developed to severe levels and caused crop damage.

"The disease did not begin spreading from the mid-Gulf South," Schneider said. "It apparently didn’t overwinter north of Orlando, Fla."

Schneider said the disease didn’t aggressively spread west of Alabama in 2005 because of dry conditions through the Mississippi Valley from Louisiana to Illinois.

"Because of the abnormally dry growing season in 2005, we’re about at the same level of knowledge as we were last year," Schneider said of Louisiana’s experience with the disease this year. "2005 was dry, and the disease requires rainfall.

"To truly evaluate the effects of the rust, we must wait to see what happens with normal rainfall patterns," the LSU AgCenter scientist added.

Schneider said if Louisiana got the same level of rust as Georgia and Alabama, it would be a major disease problem for growers in the state.

"It’s not something to be ignored," he said. "Growers must be prepared."

Schneider and Lanclos both cite sentinel soybean plots planted throughout the state and the rest of the nation’s soybean-growing areas as one of the best ways to detect Asian soybean rust at the earliest possible time. These plots are planted earlier than commercial fields and are monitored regularly to detect the presence of the rust.

If the Asian soybean rust is identified early in sentinel plots in an area, growers are then able to apply fungicides to protect their crops.

Schneider reinforced the importance of sentinel plots by pointing out the disease was first found in sentinel plots in Georgia and Alabama, where the Cooperative Extension Service was able to provide growers with spray advisories exactly as planned.

The LSU AgCenter plant pathologist said that if the disease becomes established in kudzu and other non-soybean host plants in areas where it had not been in 2005, it may spread differently in 2006 than in 2005 – especially with a wet spring and summer.

"There will be sentinel plots year after year," Schneider added, however.

In 2005, chemical companies also put out spore traps, but they were of dubious value, because researchers found it difficult to confirm if spores were really Asian soybean rust, Schneider said. He added that he’s working to develop technology to quickly and accurately confirm spores as Asian soybean rust.

"If we can confirm, spore traps will be exceptionally valuable," Schneider said. "Because it takes two weeks for spores to germinate, infect plants and then cause symptoms on the plants, verifiable spore traps can give growers two weeks’ advance notice of the presence of the disease and provide time to treat fields."

Asian soybean rust has been around since the early part of the 20th century, but it had been confined to Asia until recently when it spread to Africa and then on to South America. It was first discovered in the Western Hemisphere in Brazil in 2000, and officials believe hurricane winds brought it from the South American continent into the U.S. Gulf Coast region in August 2004.

The rust disease, which is spread by wind-borne spores, is feared because it’s hard to detect until it often is too late to do anything to protect the crop from damage. The symptoms first appear on the bottom leaves – hidden from view. By the time a farmer might see it, the disease, which has taken hold, has been known to destroy entire fields.

Soybean production in Louisiana is a multimillion dollar business – producing more than $240 million for the economy in 2004.


Ray Schneider at (225) 578-4880 or
David Lanclos at (318) 473-6530 or
Rick Bogren at (225) 578-5839 or
John Chaney at (318) 473-6589 or

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