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Northern blights: Corn disease could show up again

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Written Tuesday, March 21, 2006  

Northern corn leaf blight could occur in some Eastern Corn Belt cornfields this growing season, continuing the trend of high infection observed in susceptible hybrids over the past four years.

"One of two things could be happening," said Pierce Paul, an Ohio State University plant pathologist. "One is that growers are planting increasingly susceptible hybrids. Or we are seeing an increase in a specific race within the pathogen population.

"With no-till, spores of the fungus are always available, and if growers keep planting susceptible hybrids and we have favorable weather conditions at the right growth stage, we are likely to see severe northern corn leaf blight problems in certain parts of Ohio this year."

Paul will conduct research this year to characterize the resistance of the most commonly planted commercial hybrids. He also hopes to determine if there is a race shift of northern corn leaf blight populations in Ohio.

Northern corn leaf blight is a disease caused by a fungus, which survives in corn residue on the soil surface. It develops in humid, wet conditions and has the potential to reduce yields when blighting occurs between the tasseling and grain-fill stages of corn development.

The disease, most problematic in reduced tillage environments, can cause as high as 50 percent yield losses and predisposes the corn crop to stalk rot problems. At least eight races of the northern corn leaf blight fungal pathogen exist. In Ohio, Race 0 and Race 1 have been identified.

"We know that we've always had Race 0 and Race 1, but now we need to find out if the frequency of one of those races or another race is increasing in the state, or if there is a distribution difference between races throughout parts of Ohio," Paul said.

The research will take several years before any conclusive results are found. Until then, growers are advised to continue planting resistant hybrids.

"Growers should be planting hybrids with both race-specific and partial resistance to guarantee some level of protection, and to keep disease levels low, especially in fields where they are noticing an increase in the levels of the disease," Paul said.

Planting race-specific and partial resistant hybrids is the most effective means of controlling the disease. Race-specific resistant hybrids contain a specific resistance gene that prevents certain races of the fungus from causing the disease.

Partial-resistant hybrids contain several genes that provide some protection against all known races of the fungus. Unlike race-specific resistance that provides complete protection against a specific race, partial-resistant hybrids exhibit some disease symptoms, but are not severe enough to damage the plants.

"Growers should be going to their seed companies and asking for race-specific and partial-resistant hybrids to help control northern corn leaf blight," Paul said.

For more information on northern corn leaf blight, log onto http://agcrops.osu.edu/ and click on "Diseases" under "Crop Info" on the left side of the page; or download OSU Extension Fact Sheet AC-20-02 on Ohioline, located at http://ohioline.osu.edu .

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