December 29, 2005

 

More Asian soybean rust found in US state Alabama

 

 

The USDA has announced the discovery of Asian soybean rust in Mobile County, Alabama, which becomes the 138th US county to be affected by the plant disease in 2005.

 

The infection was found by Auburn University plant pathologist Ed Sikora.

 

"On Dec 21, soybean rust was detected on the last two green leaves of a one-acre kudzu patch in Mobile County in southwest Alabama," he reported via the USDA's public rust Web site. "Cold temperatures should kill most kudzu in south Alabama by mid-January."

 

A rust update published Tuesday by USDA said the seasonal freeze line, (marking locations that have experienced minimum fall/winter temperatures equal to or lower than 32 degrees Fahrenheit), currently extends from near Corpus Christi, to north of Houston and Beaumont, Texas then to around New Orleans, Louisiana.

 

Temperatures have fallen below freezing point on the Mississippi coast, ending the local growing season and causing what USDA terms "kudzu dieback" (100 percent defoliation), thereby preventing the weed from serving as a winter host for soybean rust.

 

"There is currently 100 percent dieback (which) extends northward from south-eastern Texas to central Louisiana, southern Alabama, central Georgia, eastern South Carolina and the coastal areas of North Carolina," said the agency.

 

Texas cooperative extension service plant pathologist Tom Isakeit said the single most feared rust infestation found in the US during 2005--on a kudzu patch in Liberty County, Texas--is now "approximately 90 percent dead. Green leaves with abundant rust pustules can still be found, but these leaves seem to be drying out."

 

Some crop-weather experts estimate that, due to prevailing wind circulation patterns, the risk of rust infecting the core of the Mid-western soybean belt in any season rises four-fold if the disease successfully survives the winter, known as overwintering, in Texas or western Louisiana.

 

It appears that Florida may yet serve as an incubator for the disease, creating a situation very similar to that seen this past season, when the disease overwintered in that state and then moved gradually across the south-east.

 

"We have not had a severe frost in the Florida panhandle yet, and a lot of kudzu leaves are still green," University of Florida plant pathologist Jim Marois told USDA. "Rust spores are still being produced on the infected kudzu, with abundant sporulation on warm days."

 

The airborne fungus has now been found in 33 counties of Alabama, 23 counties of Florida, 35 counties of Georgia, one county in Kentucky, two counties in Louisiana, two counties in Mississippi, 18 counties in North Carolina, 23 counties in South Carolina and one county of Texas.

 

Asian soybean rust is widely considered to be one of the world's worst plant diseases, causing rapid premature defoliation of soybeans and near-total yield losses, unless checked with chemical fungicides.