WOOSTER, Ohio -- An old corn disease has re-emerged in Ohio fields, raising concerns of potential problems it may cause if not effectively controlled.
Northern corn leaf blight, a fungal disease that can cause significant yield losses under wet weather conditions, has been found in cornfields throughout southern Ohio this season. The disease was last seen in Ohio during the early 1990s.
Pat Lipps, an Ohio State University plant pathologist, said the disease could potentially cause serious problems and should be monitored closely. "The cases we've been finding in Ohio are not severe enough to be a major epidemic, but it's enough to give us a warning sign - that we need to pay attention to this," said Lipps.
Plant pathologists speculate the disease has returned due to the planting of corn hybrids that lack resistance. "The best way to control the disease is through resistance. It's cheap and effective. The farmer just needs to take the time to work with seed companies in choosing a resistant hybrid," said Lipps. "There are plenty of hybrids available with good resistance." Northern corn leaf blight is more common in fields throughout southern Ohio due to the ample rainfall the region received throughout the growing season. Lipps said a number of fields with higher disease levels are experiencing 10 percent to 20 percent yield losses.
The telltale sign of northern corn leaf blight is 1- to 6-inch long cigar-shaped gray-green to tan-colored lesions on the lower leaves. As the disease develops, the lesions spread to all leafy structures, including the husks. The lesions may become so numerous that the leaves are eventually destroyed causing major reductions in yield due to lack of carbohydrates available to fill the grain. Yield losses can reach as high as 30 percent to 50 percent if the disease establishes itself before tasseling.
Two types of resistant hybrids are available to farmers to control northern corn leaf blight: partial resistant hybrids, which protect against all four of the known races of the fungus, and race-specific resistant hybrids, which protect against a specific race. Partial resistant hybrids are the most common. A one-to two-year rotation away from corn and destruction of old corn residues by tillage may be helpful in controlling the disease if susceptible hybrids must be grown.
For more information on northern corn leaf blight, log on to Ohio State Extension's Ohio Field Crop Disease at http://www.oardc.ohio-state.edu/ohiofieldcropdisease. Ohio State's Ohioline at http://ohioline.osu.edu also contains information about the disease and how to choose effective hybrids.