Asian soybean rust has been discovered in an Iberia Parish kudzu patch in south Louisiana. Also the location for the first Mid-South case of ASR in 2006, the latest find was 53 days earlier this year.
“ASR is showing up earlier and earlier and as that happens, the implications for the soybean industry become more and more severe,” says Clayton Hollier, LSU AgCenter plant pathologist. “The implications are very big not only for our industry in Louisiana, but most immediately, for those in adjoining states.”
In the latest case, the ASR was producing spores, was confined to a small area — about 10 feet by 10 feet — and “was ready to roll,” says Hollier.
This is the fourth year in a row that ASR has been found earlier in the year.
“In 2004, it was found in November,” says Boyd Padgett, LSU AgCenter plant pathologist. “In 2005, it was first found in October. Last year, the first positive report was on June 30. This year, the announcement was made on May 11. If that's not a trend, it's close to one.”
All interviewed stress the find was on kudzu, not nearby sentinel plots or soybean fields.
“We've been doing routine, weekly sampling of kudzu on known ASR hosts through the winter and have continued that into the growing season,” says Hollier. “When my associate found something curious, we went through several diagnostic processes and, sure enough, all were positive for ASR. But we wanted to make very sure, so we ran a PCR (genetic) test, as well.”
Is the earlier discovery date surprising?
“Not at all,” says David Lanclos, LSU AgCenter soybean and corn specialist. “If you look at the historical pattern of the disease and weather we've had — mild winters and deep south Louisiana not getting freeze coverage — that allows (the disease to remain viable) in the layers and layers of kudzu leaves.
“Check out South American accounts on how they've dealt with ASR. The first couple of years were minor. After that, ASR grew worse and worse until it became an epidemic.”
That doesn't mean the United States will see the same.
“I'm still optimistic we won't see an epidemic,” says Lanclos. “The weather could turn out hot and dry next week and the disease would be shut down for another month or two.”