WOOSTER, Ohio -- Northern corn leaf blight may occur throughout parts of Ohio's 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. One is that growers are planting increasingly susceptible hybrids. Or we are seeing an increase in a specific race within the pathogen population," said Pierce Paul, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center. "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 the state this year."
Paul, who also holds an Ohio State University Extension appointment, will launch studies this year to characterize the resistance of the most commonly planted commercial hybrids and 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," said Paul.
The research will take several years before any conclusive results are found. Until then, growers are recommended 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," said Paul.
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 will prevent 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," said Paul.
For more information on northern corn leaf blight, refer to http://agcrops.osu.edu/ and click on "Diseases" under Crop Info on the left side of the page, or refer to OSU Extension Fact Sheet AC-20-02 on Ohioline at http://ohioline.osu.edu.