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Know your corn diseases

Jeff Caldwell 08/25/2010 @ 2:27pm Multimedia Editor for Agriculture.com and Successful Farming magazine.

As corn harvest nears in the Midwest, farmers say they're finding some issues in both crops that they worry might cause some yields to slip from the top end.

"During the last week many people have noted deterioration of upper leaves in the corn canopy," says Iowa State University (ISU) Extension agronomist in Muscatine, Iowa, Virgil Schmitt.

The corn's showing signs of Goss's wilt, say farmers like Agriculture.com Marketing Talk member dapper7, who says in his location in northwest Iowa, "scattered fields of corn appear to be dying prematurely."

But, it can be tough to distinguish between Goss's wilt and northern corn leaf blight, another common disease this time of year that shows similar symptoms. "Depending on the field, there often is more than one reason, some of which look very similar," Schmitt says.

Iowa State University plant pathologist Alison Robertson points out a few differences between the 2 diseases here.

Then there's antracnose top die-back, another similar disease. It takes a close look to tell the difference between top die-back and Goss's wilt, Schmitt says.

"Both Goss's wilt and anthracnose leaf blight can have 'freckles.' Look at the freckles under 20X or more magnification; if they are 'porcupine-like,' it is anthracnose," he says. "If the lesions have a shine, like varnish, that is dried exudate or ooze from Goss's wilt."

The bad news is there's not a whole lot to do about any of these diseases. "The bottom line, however, is that there is nothing that can be done to slow down or stop any of them at this point in time," Schmitt adds.

The good news is, depending on your location, harvest may not be far off. Agriculture.com Harvest is moving along briskly in the deep and mid-South, and with some farmers starting combines in Missouri and parts of Illinois, widespread harvest won't be far off in the Midwest.

"For corn located near Kansas City, St. Louis, and parts of southern Illinois, some farmers are reporting 20-21% moisture," reports Agriculture.com Markets Bureau Chief Mike McGinnis. "That is low and nearing harvest-ready."


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