September 15, 2006

 

Soybean rust hits US state North Carolina

 

 

Asian soybean rust has been found in North Carolina for the first time this year, reported early Thursday (Sep 14) by state disease management officials on the US Department of Agriculture's public rust website.

 

"Asiatic soybean rust was identified on soybean samples collected from a mobile sentinel plot on Sep 13," said North Carolina State University plant pathologist Steve Koennig. "The soybean leaves were collected from near Tabor City in Columbus County."

 

Columbus County is located in the extreme south-eastern portion of North Carolina, bordering South Carolina.

 

Koennig indicated that the discovery should not be of great concern to local soybean growers, as development of the airborne fungus has occurred very late in the 2006 growing season.

 

"Ninety-one percent of the (North Carolina) soybean crop has set pods. Thus about 85-95 percent of the crop is no longer at risk," he said. "Soybeans that have full-sized soybeans in the pods, before rust is identified in the field, will probably mature before rust causes significant yield loss. If rust gets within 100 miles, and the soybeans do not yet have fairly good sized seeds in the pods, we suggest spraying with a strobilurin fungicide."

 

The plant pathogen flourishes in warm, damp, overcast weather, causing premature defoliation of immature soybeans and sometimes major yield losses, unless countered with fungicide.

 

Officials also reported new infestations of rust in sentinel plots in Sumter County of western Georgia, and Jefferson County of extreme south-eastern Texas on Thursday.

 

"There is a total of 55 counties in eight states with rust this year," said USDA. "Including five in Alabama; 13 in Florida; 10 in South Carolina and Louisiana; 11 in Georgia; three in Texas, two in Mississippi and one in North Carolina."

 

The North Carolina find has heightened rust surveillance in the adjoining state of Virginia, although no fungicide applications are yet being recommended.

 

"Weather conditions are favourable in Virginia for infection, but no soybean rust has been found in any of the 10 sentinel plots that are being sampled weekly, nor has there been any rust detected in the 40 commercial fields that are being scouted," Virginia Tech plant pathologist Erik Stromberg told USDA. "At this time full-season soybeans are in the R6 (full-seed) development stage; therefore this crop is no longer be at risk for soybean rust in 2006. Double-crop soybeans will be at risk for another 2 to 3 weeks."

 

A rust infection forecast updated by USDA Thursday said high humidity levels will continue to put the Carolinas at risk of new outbreaks for the next few days, with some increased risk also emerging in eastern Texas, Louisiana and eastern/central Georgia, "due to winds pushing airborne spores back into the region".