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Corn+Soybean Digest

First ’07 Midsouth ASR Case

Asian soybean rust has been discovered in an Iberia Parish kudzu patch in south Louisiana. Also the location for the first Midsouth 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 ft. by 10 ft. – 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 U.S. 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.”

Still, the early ASR find means Louisiana’s soybean crop – now in the earliest growth stages – “faces the possibility for early, or multiple fungicide treatments,” says Hollier. “That doesn’t mean it will ever happen. But with this disease showing up so early, those things are in play, while they weren’t before.”

Right now, “everyone is talking about corn fungicides,” says Lanclos. “Bean fungicides haven’t been in the conversation — and that’s good because there’s no need. We continuously try to educate growers on what to do with ASR and that message is reaching them. If necessary, we’ll have more recommendations when the beans approach a stage when a fungicide might pay dividends.”

Above all, the AgCenter colleagues insist that ASR is a manageable disease.

“We’ve had experience with it and know we can manage it,” says Padgett. “There are other diseases (deserving attention), including aerial blight.”

Lanclos points to cercospora leaf blight, for which “there’s little, or no, chemical controls,” as a big fear. “I’m much more worried about cercospora leaf blight than ASR.”

In Louisiana, corn is currently king.

“At this point, I don’t think we’ll see soybean acreage approaching last year’s 830,000” says Lanclos. “I’m very comfortable saying we’ll be down 10 percent in bean acreage and there are rumors of more.”

With about 200,000 soybean acres left to plant in the state, southwest Louisiana remained very wet. With few exceptions, farmers in the area had been unable to plant. Those growers will have to factor in the ASR announcement.

However, “at this point, this ASR find would not deter me from planting soybeans anywhere in Louisiana,” says Lanclos. “And that goes back to my earlier statement: this is a manageable disease. It may cost us more money to grow, but it’s manageable. No panic.”

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