Asian soybean rust - a serious fungus to soybean crops - has been found in the Texas Valley at Weslaco, where prevailing winds could help spread the disease.
Scientists think fungal spores from South Texas could ride the winds to he Midwest's multi-billion dollar soybean crop. Dr. Marvin Miller, a Texas Agricultural Experiment Station plant pathologist, found the fungus on soybean leaves on Feb. 14 in a research field plot at Weslaco. Preliminary diagnosis was made at the Texas Plant Disease Diagnostic Laboratory in College Station, and later was confirmed by the USDA laboratory in Beltsville, Maryland.
"Soybean production here in South Texas isn't significant, but this is of great concern to the production areas of the Midwest," Miller notes. "In addition to soybeans - cowpeas, green beans, and other edible legumes could be affected by this fungus which causes defoliation and yield reduction."
Soybean rust fungus was first introduced into the United States through Florida in 2004 - likely aboard hurricane winds, but confined itself to the Southeast, says Dr. Tom Isakeit, Texas Cooperative Extension plant pathologist, College Station.
"This finding in South Texas is probably a new introduction," Isakeit says. "And what it suggests is that soybean rust could take the so-called 'rust corridor' to points possibly a far north as Canada."
Prevailing winds have been blamed for moving other rust diseases on a northerly path, like southern rust of corn, stem rust in wheat, and common rust of corn.
Joseph Krausz, scientist at Texas A&M University department of plant pathology, says finding soybean rust in both Mexico and Texas is significant.
The recent occurrence in South Texas, and Mexican states of Tamulipas and San Luis Potosi late last year, could be the first step to the pathogen becoming endemic in the rust corridor - south to north - he notes. Environmental conditions will play a big role in any further establishment of the rust in the corridor, he adds.
"Rust spores can be carried by wind currents hundreds or even thousands of miles - even across oceans," Isakeit notes. "They are eventually brought down to earth by rain, and a leaf that's been wet for several hours is needed in order for a spore to germinate and infect a plant."
But once a plant is infected, the fungus can multiply rapidly, Miller adds.
--Rod Santa Ana III is with Texas A&M Communications.