February 14, 2006

New discovery of Asian soybean rust in southern US

Thomas County, in southern Georgia, is the latest location in the US found to be harbouring Asian soybean rust.

University of Georgia researcher Layla Sconyers reported discovery of the airborne fungus, at a site situated just north of the Florida-Georgia border, to the US Department of Agriculture late Friday, Feb 10.

"Kudzu was found growing and protected in a concrete culvert," she said. "A few older leaves and some new green leaves (3-4 weeks old) were found. Soybean rust pustules were found on the older leaf tissue."

No soybean rust was found in the county last year, although the disease eventually appeared in more than 135 counties of 9 southern states, from Texas to North Carolina.

Sconyers indicates that it appears the culvert effectively insulated the kudzu from sub-freezing temperatures that struck the area during the latter half of last week saying, "There was no sign of frost injury."

USDA said scouting for soybean rust continues on kudzu patches from Florida northward through Georgia and Alabama, and westward to Texas. The disease has been found in one county of Alabama, 2 counties of Georgia and 10 counties of Florida, thus far in 2006.

"Most kudzu patches scouted north of central Florida have been defoliated; and some are just beginning to leaf out," said the agency. "It is unknown whether soybean rust is distributed more widely in the southern US in early February 2006 than it was one year ago."

Asian soybean rust is a major plant pest of soybeans worldwide - and especially in South America, causing premature defoliation of plants and severe yield losses. It was first discovered in the continental US in November 2004. The disease can survive on nearly 100 plant species other than soybeans, but requires living green tissue to do so, and prefers kudzu as a winter host.