August 25, 2005

Spores detected in Suffolk, but no soybean rust

SUFFOLK—A single cluster of six unrediniospores comparable to the those of Asian soybean rust was detected in a spore trap at Virginia Tech’s Tidewater Agricultural Research and Extension Center during an Aug. 3-10 air sampling.

Soybean rust is an aggressive airborne fungal disease. While it poses no threat to human health, it causes soybean plants to defoliate and can result in reduced yield and diminished seed quality.

According to officials with Virginia Tech and Virginia Cooperative Extension, the spores in question fit the morphological description of the unrediniospores of Asian soybean rust, but a definitive identification requires serological or morphological analysis.

“The weather condition around the time of deposition was extremely hot and dry and not conducive for promoting the infection process,” said Dr. David Holshouser, Extension plant pathologist and soybean specialist. “Examination of the adjacent sentinel plots and other soybean fields nearby revealed no indication of Asian soybean rust.”

At press time, officials had not recommended applying fungicide to Virginia’s current full-season soybean crop.

“Once the crop reaches R6 stage, very little yield loss will occur from new infections,” Holshouser said. “On the other hand, our double-crop soybeans are three to four weeks away from the R6 stage. We will need to pay close attention to our double-crop soybean fields if soybean rust is detected in Virginia within the next few weeks.”

Virginia Tech has an intensive program for detecting soybean rust and alerting growers. It includes spore traps in Orange, Painter, Suffolk and Warsaw, and an extensive scouting program across soybean production areas. Scouts are checking more than 90 fields weekly for the presence of soybean rust and aphids.

Reports on the status of disease spread and field scouting are posted twice weekly at www.ppws.vt.edu/ipm/soybeanrust/index.htm and recorded updates by phone are available at 804-657-6450, ext. 103.

“This just tells us that there are spores in the area,” Holshouser said. “Our level of alert has been raised, but not our level of risk.”

Soybean rust has been identified in several Southern states, including Alabama, Florida, Georgia, Mississippi and, most recently, South Carolina, where an outbreak was detected on Aug. 17 in a field on the Savannah River.

Extension officials advise soybean growers to be vigilant and scout fields at least weekly, and to report any findings to their local Extension agents.

Contact Holshouser at 757-657-6450, ext. 123.