September 23, 2008
Heavy rains generated by late-summer hurricanes have caused an explosion in Asian soy rust infections across the Deep South, although experts say the plant disease poses little threat of significant yield losses in major growing areas of the Midwest.
The USDA said Sunday infections had been discovered in 18 counties across Alabama, Arkansas, Georgia, Mississippi and South Carolina in the past four days.
Since January, Asian soy rust has been found in 12 counties in Alabama, 12 counties in Arkansas, 13 counties in Georgia, 22 counties in Florida, four parishes in Louisiana and 22 counties in Mississippi.
Soy rust is expected to spread northward until frost, according to the USDA.
The USDA's latest infection forecast said transport of rust spores "will be rather minimal over the Southeast as winds will be from the east, keeping any risk of long distance transport minimal."
However, winds from the south over Texas and Arkansas would increase the risk of transport into southern Missouri, the report said.
Even though the USDA Agricultural Statistics Service estimates 5.3 million acres of farmland were planted to soy in Missouri this season, that area is generating little concern about potential yield losses.
As crops in Missouri were planted in May, it has reached the R6 (full-seed) growth stage, and rust that develops now would not suppress yield, said University of Missouri plant pathologist J. Allen Wrather. Late planted soy will be at R6 by early October so the threat would be minimal as well.
Soy rust damages yield by causing premature defoliation of infected plants
It is a major plant pest in South America and Asia and first appeared in the US about five years ago.