Southwest Louisiana Growers Need Fungicides To Fight Asian Soybean Rust

David Y. Lanclos, Saichuk, John K., Schultz, Bruce  |  7/29/2006 12:49:48 AM

News Release Distributed 07/28/06

MOWATA, La. – Asian soybean rust has surfaced in Louisiana at the prime time for fungicide applications on soybeans in the southwestern area of the state, according to an LSU AgCenter expert who spoke here Thursday (July 27).

The comments from Dr. David Lanclos, the LSU AgCenter’s soybean specialist, came during a meeting hosted by G&H Seed of Crowley.

Lanclos said most soybeans in Southwest Louisiana are in the third of the six reproductive growth stages of soybeans plants. That’s the optimum phase to apply fungicides, which could help to ward off rust damage, according to Lanclos.

Just one day before, on Wednesday (July 26), scientists confirmed the discovery of Asian soybean rust in a sentinel plot of soybeans at the LSU AgCenter’s Dean Lee Research Station near Alexandria. Lanclos said, however, that no additional rust was found in a follow-up inspection of plots at the station Thursday.

If a plant can get to the last reproductive stage before Asian soybean rust hits a field, experts say the disease will not have much effect on the crop.

That’s already the situation for soybeans planted in North Louisiana, Lanclos said, but farmers in the southwestern corner of the state had to delay planting because of unfavorable conditions.

Lanclos said the sentinel plot at the Dean Lee Research Station has been sprayed with a fungicide. It also will be killed with paraquat and then plowed under.

The soybean disease also was discovered earlier this month in patches of kudzu, another potential host for Asian soybean rust, in southern Louisiana. Those kudzu patches in Lafayette and Iberia parishes were left intact, however, because kudzu cannot be controlled.

"It’s an unfortunate situation, but we can’t destroy it," Lanclos said.

The LSU AgCenter specialist said the disease can move a considerable distance in just a few hours. It is spread by spores and is believed to have entered the country a couple of years on storm winds that brought it from South America – which, up to that point, had been the closest point where Asian soybean rust was found.

"If it gets in the jet stream, it can travel 300 miles a day," Lanclos said of Asian soybean rust, which can potentially wipe out soybean crops.

In addition, during the Thursday meeting, Lanclos said another disease, a fungal one known as aerial blight, could cause as many problems for farmers as Asian soybean rust.

"With these weather conditions, they are blowing and going," Lanclos said.

If signs of disease surface, Lanclos stressed farmers should not delay spraying fungicides.

Moving to another disease, LSU AgCenter rice specialist Dr. Johnny Saichuk said cercospora, a disease usually associated with soybeans, is widespread this year in rice fields.

Saichuk said none of the rice fungicides currently labeled or approved for use in rice are very effective at controlling this disease. And he said it’s possible fungicides used on rice to fight other diseases may have allowed cercospora to flourish.

The problem is complicated because a rice plant loses natural defenses as it matures, he said.

The LSU AgCenter rice specialist said it’s possible cercospora could affect a second rice crop, but that’s not been proven.

Michael Hensgens of G&H said the disease has shown up in all varieties of rice, including hybrids.


David Lanclos at (318) 473-6530 or
Johnny Saichuk at (337) 788-7547 or
Bruce Schultz at (337) 788-8821 or

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