The LSU AgCenter announced Asian soybean rust had been found in a Louisiana kudzu patch south of Lafayette near New Iberia on June 30. Late in the day on July 7, another infected kudzu patch was announced — this time in Iberia Parish, only a few miles from the original find. At both sites the disease is sporulating vigorously.
ASR has not been found in Louisiana soybeans.
Commentary on the finds at the USDA’s ASR-devoted Web site ( http://www.sbrusa.net) says “three generations of pustules can be found at each location. At the Lafayette site, spread of disease is occurring in the kudzu…
“What does this really mean for the soybean industry? The presence of ASR in kudzu, with no sightings in soybeans, means that soybean fields need to be scouted at least every two to three days especially in areas along tree lines that are shaded in the morning. These shaded areas maintain longer dew periods and can reduce temperatures enough to encourage ASR development if the spores are present.”
This advice is solid as Blaine Viator, a prominent sugarcane consultant in south-central Louisiana, found the first infected kudzu in a low-lying area beneath a tree. The region had been receiving intermittent showers, so moisture had been available to the disease.
The infection on the samples Viator brought to LSU was “very heavy,” said Ray Schneider, LSU AgCenter research plant pathologist on July 7 prior to the second ASR find being reported. “To me, that suggests that there had been a substantial spore shower probably, about, three weeks ago. The innoculum is blowing in from somewhere — perhaps Texas or Mexico. Spores are arriving and have been for some time.”
Does Louisiana have the conditions favorable for disease development?
“Certainly, for the past few, rainy days, we have. However, even if infection has occurred in the last few days, ASR won’t show up on leaves for the next 10 days, or so. And that’s at the earliest.”