Ohio Farmer

Delayed planting allows more time for pathogen spores to multiply.

August 8, 2019

3 Min Read
cornfield
DISEASE THREAT: Fungal diseases that can infect either soybeans or corn can survive through the winter on the crop residue left in a field after harvest.Mac99/Getty Images

Late-planted corn and soybeans could be vulnerable to higher-than-normal levels of crop diseases this year, experts from Ohio State University warn.

When sown one to two months later than usual, corn and soybeans stand a greater chance of succumbing to diseases, especially fungal diseases.

Dry weather across much of Ohio since July has helped stave off some disease spread, because fungal diseases need moisture to thrive. Still, during a year when late planting has already limited the yield potential on crops, it’s critical to be vigilant for other threats, too, including all types of diseases, molds and insects, experts with OSU’s College of Food, Agricultural, and Environmental Sciences (CFAES) advise.

Fungal, other diseases threats this year

Fungal diseases that can infect either soybeans or corn can survive through the winter on the crop residue left in a field after harvest, says Pierce Paul, a CFAES specialist in corn and small grain diseases. Spores of the pathogens that cause the diseases form in the spring and spread. Delayed planting allows more time for the spores to multiply.

Not only are more spores potentially available to infect a new corn or soybean plant, but the plant, if sown later, is more likely to be infected in an early growth stage, Paul says.

Corn growers should watch for signs of gray leaf spot disease, the most common corn disease across the Corn Belt, Paul says. Northern corn leaf blight and tar spot — a new disease in Ohio — are also potential threats to this year’s crop, he adds.

“People need to be vigilant. This is the time to walk your fields and see if there’s signs of disease,” Paul says.

In Ohio and across the Midwest, both corn and soybeans were planted one to two months late because of unprecedented rainfall levels. Many acres were not planted with either crop, and instead, will be planted with cover crops. Insurance claims will also be filed to compensate for the profit loss. Claims will be made on about 20% of Ohio’s acres that typically hold cash crops.

Frogeye leaf spot danger to soybeans

In soybean fields, growers should be most concerned about frogeye leaf spot, because the incidence of that disease has been increasing every year in Ohio, says Anne Dorrance, a CFAES soybean pathologist.

Some varieties of soybeans are susceptible to the disease, she says.

If frogeye leaf spot infects a soybean plant just before or during the growth of the bean pod, “we could have significant yield losses,” Dorrance says.

Cercospora leaf blight and downy mildew, a water mold, are also potential threats to this year’s crop along with Phomopsis, which was a major problem last year, Dorrance says.

“We even have soybeans that were planted at a normal time this year that are already showing symptoms of fungal diseases,” she says.

Some varieties of corn and soybeans are resistant to various diseases, so growers would benefit from knowing which fungal diseases their planted variety can fend off. But resistance does not mean immunity; it only means that damage to a resistant plant will be milder.

“Walk your fields,” Paul says. “Walk more frequently this year to see what’s there and how it’s progressing.”

Check for insect damage, too

Besides watching for signs of diseases, growers would also benefit from scouting their fields for damage from insects.

“With dry weather, plants tend to grow slower, and insects might be able to keep up with the crop’s growth,” says Harold Watters, an OSU Extension agronomy field specialist.

But before investing in pesticides, growers should determine how big the problem is, he says.

“I would caution folks not to overspend,” Watters says. “On the other hand, during a year when yields are already expected to be lower, we do need to protect what little we have.”

For more information about disease or insect threats on late-planted crops, visit OSU’s corn disease help, soybean disease help or stinkbug help webpages.

Source: OSUE: which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.

 

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