This fall in fields with severe lodging, corn harvest started early. With dry weather, it was good to begin in September as soon as grain moisture content declined. “We know if it starts raining, we’ll have the mold issue to worry about with all these cornstalks lying down,” said Don Van Dyke, as he harvested corn Sept. 23 in a field near Grinnell in Poweshiek County.

“We have to drive slowly to get this downed corn into the combine. It takes extra time to harvest these fields,” he said. “We had drought in 2012, but 2020 brought drought plus a derecho, a hurricane-force windstorm. In my 40 years working on farms and being around farming, I’ve never seen a harvest like this one.”

The yield monitor showed the field Van Dyke was harvesting that day was averaging 150 bushels per acre. The field was 95% or more picked clean in the downed corn areas. Significantly fewer ears than expected were left on the ground after the combine went through. In a year without a drought and derecho, this field would have hit 200 bushels or more per acre.

Dan Dunsbergen, manager of Key Co-op’s Grinnell location, said the actual production history for this field and similar ones in the area is 185 to 230 bushels per acre. So even without the derecho, yields in 2020 are probably 50 to 60 bushels below normal just due to drought.

Related:Iowa corn: Down but not out

“Our crops today are bred to handle stress,” Dunsbergen said. “But with everything that’s happened this year and fields getting shutdown before Labor Day, this is a year you don’t want a do-over; you just want it over with. I’m reminding our farmers, it’s only six more months until spring.”

Key Co-op is encouraging farmer-members to collect grain samples from fields. The co-op is running tests on corn for mycotoxins. “We haven’t seen any problems yet; it’s early in the harvest season,” Dunsbergen said on Sept. 23. The co-op has been  sampling every 10th load. “When more corn starts coming in, we will be sampling and testing more.”

At the co-op’s feed mill, corn must be below 20 parts per billion for aflatoxin if made into feed for sows with nursing pigs. For chickens, it’s 20 ppb. For cattle, it’s 300 ppb. “We haven’t reached those levels yet, and as long as we don’t get rain on this downed corn, we’ll likely be OK,” he said.

Testing for mycotoxins

The Key Co-op uses a quick test to see if aflatoxin is present in a corn sample. The co-op does not test with a black light. Instead, it grinds a corn sample into a mash, puts it in solution and uses a litmus test. If the sample comes in at 20 ppb or greater for aflatoxin, corn from the sample is sent to the Iowa State University Grain Quality Lab or a commercial lab to get an exact reading.

If it reaches 20 ppb, “we start zeroing in on where the corn sample is coming from,” Dunsbergen said. “The last time we did this spot-checking was 2012, a drought year. It’s critical to test for aflatoxin when it’s a threat. Our Grinnell feed mill uses about 170,000 bushels of corn per week going into livestock feed.”

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

Keep up communication

If dealing with aflotoxin issues, talk with your crop insurance agent. Toxins are an insurable peril. Also, keep in touch with the grain elevator where you store or sell your crop. Many elevators lost storage capacity as a result of derecho damage to facilities. Likewise, many on-farm storage bins were blown down.

Farmers are wrestling with how and where to store and handle this crop, and need to keep the stored grain in good condition. Some will use temporary storage such as big plastic bags and machine sheds. Some will be doing more hauling to different elevators.

Meanwhile, “we keep plugging away,” Don Van Dyke said. “Harvesting downed corn is like harvesting soybeans. If there’s moisture on the crop in the field, I can’t run the combine. That’s especially the case with downed cornstalks. With heavy dew on cornstalks and cool mornings, you can’t start harvesting right away. You may have to wait until 11 a.m. or noon. When mornings start with heavy dew, stalks won’t flow into the header. Same thing at end of the day. Once stalks get tough, it’s quitting time.” 

Watch for corn quality issues

The Aug. 10 derecho left fields with broken, uprooted and damaged corn across a major area of Iowa. Paired with drought conditions across the state, growers should be on the lookout for mycotoxin issues in this year’s crop. Iowa State University grain quality specialists Charlie Hurburgh and Erin Bowers offer the following considerations for harvest, mycotoxin testing and storage:

Harvest, storage of damaged grain. Mycotoxin contamination is an insurable loss, but for aflatoxin and fumonisin adjustment, the corn must still be in the field. Affected grain that is harvestable should be harvested and dried as soon as possible after communicating with your insurance adjuster.

Harvest and handling should be gentle; mechanical injury will worsen mold issues that started in the field. Drying and cooling the grain quickly is necessary to hinder fungal growth and further mycotoxin production. In the time between harvest and drying, mycotoxins will continue to increase. Avoid using low-temperature or natural air drying, as this just serves as an incubator for aspergillus fungi. Dry the grain to 1 to 2 percentage points below what you would for sound, healthy kernels. Affected grain should be harvested, handled and stored separately, if possible.

Mycotoxins in bin’s core. The core will likely contain higher levels of mycotoxins than the rest of the bin, as mycotoxins tend to be associated with broken, damaged and lightweight kernels and fines. The same idea applies for fractions of kernels removed from sound grain by mechanical grain cleaners. Move affected grain out quickly, as it will not store.

Grain sampling and testing. Mycotoxin contamination is often unevenly distributed among corn ears in a field and kernels on individual ears. It can be quite variable, and contamination levels can vary widely among individual kernels. It takes small amounts to cause negative health effects — parts per million for fumonisins and parts per billion for aflatoxins. The low levels that must be detected, combined with the varied distribution of contamination, make sampling and testing corn for mycotoxins difficult.

Ideally for a sample to be representative, 10 pounds of shelled corn obtained from a variety of places in a field, truck or other lot would be ground, homogenized and subsampled to obtain a final test sample. If only the amount of material needed for the final test is ground, the total error in the test result skyrockets. Thus, test results are highly unreliable if a representative sample (10 pounds) isn’t used. 

With aflatoxins, as few as 70 to 80 aflatoxin-contaminated kernels in a bushel (56 pounds) can limit grain end use, so grinding a large enough representative sample is key to obtaining a reliable estimate of the true concentration. Samples that are too small normally give low results, with a few giving very high readings.

At points of first receipt of grain from growers, buyers may use some form of rapid test, which can give results in about 20 minutes. This may be performed on individual trucks or on composite samples representing multiple deliveries. Samples can also be sent to testing labs for analysis.

Use of grain. At the elevator, high throughput and limited drying and storage capacities will limit testing capabilities and the ability to segregate problematic lots “on the fly.” Adjustment in the field may help reduce the testing burden and unnecessary commingling of potentially highly contaminated lots. Aflatoxin is an adulterant from a human and animal food safety perspective; blending aflatoxin-contaminated grain with lower- or non-contaminated grain for the purpose of lowering the overall aflatoxin level is illegal. In severe aflatoxin years, however, the Food and Drug Administration has granted blending permissions for specified regions, under supervised conditions with documented and approved end uses.

Mycotoxins are heat-stable and nonvolatile; once in grain, they can’t be destroyed through processing or treatment. Thus, it’s important to direct contaminated grain to a tolerant end user.

There are acceptable uses for corn with aflatoxin concentrations up to 300 ppb. The FDA action levels are from 20 to 300 ppb. End uses that are sensitive to aflatoxin-contaminated corn include anything with human-food end use, dairy cattle (a metabolite of aflatoxin transfers into milk) and fuel ethanol producers. Aflatoxins, fumonisins and other mycotoxins are concentrated three times in dried distillers grain with solubles relative to the level in the corn used for ethanol production.

Visit the Iowa Grain Quality Initiative for more information.