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Published March 27, 2012, 03:00 AM

Crop disease challenges bean farmers

Anthracnose a big concern; white mold a worry, too
Area dry bean and soybean farmers will face some new, or at least expanded, challenges this growing season. Dry bean producers are confronted with anthracnose, a little-known disease that can hammer both yields and quality. Soybean producers, in turn, could face more problems with white mold, a crop disease that dry bean producers have battled for years.

By: Jonathan Knutson, Agweek

Area dry bean and soybean farmers will face some new, or at least expanded, challenges this growing season.

Dry bean producers are confronted with anthracnose, a little-known disease that can hammer both yields and quality.

Soybean producers, in turn, could face more problems with white mold, a crop disease that dry bean producers have battled for years.

Of the two, anthracnose is the bigger threat, says Sam Markell, North Dakota State University Extension Service plant pathologist. He’s familiar with both crop diseases.

White mold needs to be taken seriously. But it can be treated with fungicide, and area farmers and extension officials generally recognize when the disease is present in a field, he says.

However, anthracnose is relatively new in this part of the country. Nor can much be done to combat it once a field is infected, he says.

Current conditions could allow the disease “to snowball. We need to nip it in the bud,” Markell says.

Using certified seed that’s free of anthracnose is the best way to control its spread, he says.

One sign of how seriously area dry bean growers take the threat of anthracnose: the cover story of the spring 2012 issue of the Northarvest Bean Grower, a publication of the Northarvest Bean Growers Association, is devoted to anthracnose.

The association has members in North Dakota and Minnesota.

“Anthracnose could have a devastating impact on our industry and we all need to take notice,” Don Streifel, a Washburn, N.D., farmer and the association president, says in the bean grower publication.

A big role in region

Dry beans and soybeans are a big deal in North Dakota and Minnesota, and that makes diseases that threaten the crops a big deal, too.

North Dakota is the nation’s leading producer of dry beans. Minnesota ranks fourth.

Minnesota is the nation’s third-leading producer of soybeans. North Dakota ranks ninth.

Area dry bean growers have a long history of fighting white mold. For instance, a 2002 news article posted on the Northarvest Bean Growers Association’s website looks at the efforts of a North Dakota farmer to control white mold in dry beans.

But white mold is relatively new for area soybean growers.

“It’s gotten here a little faster than we’d like. But we hope we’re ready for it,” says Kurt Krueger, a Rothsay, Minn., farmer and president of the Minnesota Soybean Growers Association.

Some in agriculture think that white mold in soybeans has worked its way north from soybean fields in states to the south of Minnesota and North Dakota.

Markell says he thinks white mold, also known as Sclerotinia stem rot, has been present in this area for many years and that the region’s ongoing wet cycle has magnified its impact on soybeans.

In any case, white mold is caused by a fungus in the soil. Rain, cool temperatures, high relative humidity and moist soil favor the growth of the fungus if present, according to information from the North Central Soybean Research Program.

As the disease progresses, the fungus invades the plant stem, which can leave lesions and a covering of thick white mold on the stem.

Seed is the key

Anthracnose was first discovered in North Dakota in 2001, but had only “sporadic” impact until recently, when wet conditions favored the disease, Markell says.

It’s too soon to describe anthracnose as “an epidemic” in the area. Dry conditions this growing season would work against the disease, though not eradicate it, he says.

But if the region’s wet cycle continues, severe problems could develop, he says.

Anthracnose can be identified by long, slender lesions on leaf veins, while anthracnose lesions on the pod look like deep canker wounds, according to the information from Northarvest Bean Growers Association.

What’s particularly concerning is that anthracnose will go into the seed and doesn’t have to be visible there to be a problem, the association says.

Planting seed that’s infected can lead to big losses in yield, particularly if weather conditions are favorable for the disease, Markell says.

Fungicides aren’t effective against anthracnose, so prevention — in the form of anthracnose-free seed — is crucial, he says.

The U.S. Department of Agriculture’s Agricultural Research Service website has links to a number of resources that deal with white mold in soybeans, dry beans and other crops.

More information: www.ars.usda.gov/Research/docs.htm?docid20496.

Markell has issued an anthracnose alert. It’s available at www.ag.ndsu.edu/extplantpath.

Agweek is owned by Forum Communications Co., which owns the Herald.

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