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Black root rot suspected in Louisiana soybeans

News Release Distributed 08/07/14

BATON ROUGE, La. – Soybean growers in Louisiana are seeing soybean damage this year that LSU AgCenter scientists believe has been in cotton for many years.

Black root rot is a fungal disease that lives in the soil. And with minimum tillage or no-till situations in soybeans its presence can increase, said Trey Price, LSU AgCenter plant pathologist.

“In 2009, the disease was described as a disease of soybeans in Arkansas and has been mentioned as an issue in Mississippi over the past several years,” Price said.

Recently, Price has been receiving phone calls from growers about this problem, and he has made numerous field visits to inspect damage from the pathogen believed to be causing it.

“This disease started showing up here about five years ago, and we called it a mystery disease,” Price said. “The suspected causal agent is Thielaviopsis basicola, which has primarily been described as a seedling disease of cotton.”

Price said he is seeing the disease more than ever this year, and he believes it is more prevalent in fields that are continuously planted in soybeans.

With corn prices low and soybean prices a bit more steady right now, growers are less likely to rotate their fields. This pathogen is able to survive on plant residue, and build up in the soil, he said.

“Right now, I would say that it’s a minor issue overall.” Price said. “However, there are some fields where the damage can be anywhere from 5 to 10 percent.”

The pathogen causes black root rot in cotton, thus the name used in soybeans. Price said work is being done to determine the effects of fungicide seed treatments. Right now he’s not sure of varietal susceptibilities.

“At this time we don’t have the data to prove that rotation with corn helps,” Price said. “But I have seen a decrease in the presence of the disease where soybeans have not been continuously planted.”

This pathogen has been around for a long time. It survives in the soil and has a very large host range, he said.

“It really isn’t a very serious problem, but we want the growers to know that it is out there,” Price said.

Additional information on this disease is available at LSU AgCenter parish offices.

Johnny Morgan

Last Updated: 8/7/2014 1:51:33 PM

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