Wallaces Farmer

It’s a slower and dustier corn harvest in fields damaged by drought and the derecho.

October 6, 2020

5 Min Read
Corn being harvested
SLOW, DIRTY, UGLY: That’s how Don Van Dyke described harvesting downed corn in this field south of Grinnell, Iowa, in late September. Rod Swoboda

Much slower and dirtier than usual. That’s what harvest is like this fall for farmers whose cornfields were flattened by the August derecho. Continued drought during summer and into fall in these fields in west-central, central and east-central Iowa also weakened stalks and added to the lodging problem.

Hurricane-force winds tore across a large area of Iowa’s midsection from west to east on Aug. 10. Some stalks broke off and died. Some were pinched and flattened but stayed alive with ears on them. Other corn plants suffered root lodging, and the stalks were leaning down but stayed alive to produce a mature ear.

The problems bring questions: Will these conditions result grain quality problems? If mold develops on stalks and ears on this downed corn, will that mold produce mycotoxins in corn kernels?

Harvest 2020 requires patience

Riding in the combine cab with Don Van Dyke as he harvested at 1 mph in late September, I saw firsthand what it was like. The machine crept through the tangled, flattened cornstalks in a field south of Grinnell in east-central Iowa. Don was intently trying to get as many of those stalks and ears into the combine head as possible.

Constantly steering and trying to keep the 12-row corn head on the tangled rows, he also had his hand on the header adjustment. “The snouts need to be running on the field surface to pick up the flattened stalks and ears, but it’s hard to keep the snouts from digging into the ground,” he noted. “The unattached stalks want to bunch up in front of the corn head instead of entering it. This harvest is slow, dirty and ugly.”

Despite his intense, watchful effort and constant adjusting of speed, the corn head became plugged every so often. Don had to shut down, climb down and clean out the bunched-up stalks. Sometimes he could only harvest in one direction through the field, because of the direction the matted stalks were leaning and lying on the ground.

Why so dirty and dusty?

Some of this dirtier-than-usual harvest is due to dry weather, as drought persisted. Also, some of the dust cloud surrounding combines moving through fields is coming from a certain type of fungus that feeds on dead cornstalks and leaves.

“We were so dry toward the end of the growing season that when the corn crop reached maturity it was overtaken by saprophytic fungi that like to eat on dead leaves and other plant material,” said Meaghan Anderson, Iowa State University Extension field agronomist in central Iowa.

The saprophytic fungi have produced mold on cornstalks, leaves and ears. While this mold is causing harvest to be extra dusty and dirty, it doesn’t produce mycotoxins. Another type of fungi, the aspergillus fungus, is the one that can produce the mold that causes aspergillus ear rot, one of the most important diseases in corn. The aspergillus mold produces a mycotoxin known as aflatoxin, which grows in corn kernels. The presence of aflatoxin will affect grain quality and marketability.

Watch corn ears for mold

It remains to be seen whether aspergillus mold infestations produce aflatoxin in corn kernels this fall. A lot depends on the weather, Anderson said. So far, the weather hasn’t been conducive to allow ear molds to spread. But if it starts raining and the mat of cornstalks and ears lying on the ground or close to the ground gets wet and stays wet, that will favor production of ear molds that could produce mycotoxins.

Farmers would have a difficult time selling corn that contains aflatoxin. There are federal standards for feeding it to livestock, for example. If the concentration of toxin in the corn is high enough, aflatoxin can poison livestock and poultry if such corn is used for feed. Even if the corn is used to make ethanol, aflatoxin can concentrate in the distillers dried grain and can’t be used for livestock feed. Thus, ethanol plants won’t buy corn when tests of corn samples show the grain contains aflatoxin.

Sampling and testing corn

Grain buyers such as ethanol plants and grain elevators are spot-testing corn delivered to them this fall. Key Co-op at Grinnell, Iowa, is encouraging farmers to collect grain samples from fields and have the samples tested if farmers see mold on corn ears in the field.

In late September, the co-op was sampling and running a test on every 10th load of corn coming in. “We haven’t seen any problems yet,” said Dan Dunsbergen, manager of Key Co-op’s Grinnell location. “But we are early in the harvest season. When more corn starts coming in, we’ll be sampling and testing more.”

Key Co-op uses a quick test to see if aflatoxin is present in a corn sample. The workers grind a sample of corn to make a mash, put it in solution and use a litmus test. If the sample comes in at 20 parts per billion or greater for aflatoxin, corn from the sample is sent to Iowa State University Grain Quality Lab or a commercial lab for a more precise test to get an exact reading.

While Key Co-op has set a standard of 20 ppb or less for aflatoxin, to accept the corn, other buyers may be more stringent. Some will reject a load of corn if it’s over 10 ppb.

Keep in touch on crop insurance

“If you are a farmer dealing with aflatoxin or other mycotoxin issues, talk with your crop insurance agent immediately,” advises Dunsbergen, who is a licensed crop insurance agent. Toxins are an insurable peril. But you must have the corn checked by your crop insurance adjuster before it goes into the bin.

“For insurance purposes, quality cannot be adjusted once the grain is put in storage, either at an elevator or in bins on a farm,” he says. “Quantity, the pounds or bushels, can be measured or weighed at future times for crop insurance coverage determination. But the quality issue has to be settled and agreed on by the insurance adjuster as the corn grain comes out of the field.”

For more information about mycotoxin issues and corn quality, visit the Iowa Grain Quality Initiative at extension.iastate.edu/grain.


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