Will you see ear rots in corn this fall? If so, will mycotoxins be a concern? Mandy Bish realizes that the answers depend partly upon where you live. They also depend upon 2024 weather patterns.

“In Missouri, we haven’t experienced lots of problems recently, but much of the state was covered in drought the previous two years,” says Bish, Extension plant pathologist for the University of Missouri. “This year could be a different story. It certainly has been a different growing season.”

Bish notes that in most areas of Missouri, 2024 will go down as a relatively wet season. “We also have two corn crops this year — early-planted corn and then very late-planted corn,” she says. “Early-planted corn may be more susceptible to ear rots and molds because it matured in more humid, warm weather.”

If ear rots develop in Missouri and other western Corn Belt states, they likely will include gibberella and fusarium, Bish says. Aspergillus, which produces aflatoxin, also could appear, but it is more prevalent in drier seasons.

EAR ROT: This ear is infected with gibberella ear rot. Learn to identify it if you see it.

Tackling mycotoxin issues

Pierce Paul, longtime plant pathologist at Ohio State University, is no stranger to ear rots and mycotoxins. Today, many of his graduate students pursue projects related to learning more about how ear rot infections occur.

Related:Corn disease identified for first time in Missouri

While it was once thought fungicides couldn’t help prevent ear rots and ear molds, it is now clear that they can be a helpful tool. However, the secret is knowing when they could help. Paul has developed a model powered by algorithms to help make those predictions.

The model looks at the number of hours corn plants spend within a certain temperature range and at or above a specific relative humidity during pre-silking, or pre-R1 stage. The critical temperature is 68 to 86 degrees F, with six or more hours of 80% or higher humidity.

“We’ve determined that these diseases infect plants through silks, and these conditions increase the probability that infections will occur,” Paul says.

Right now, the model can predict conditions that favor production of vomitoxin, also known as deoxynivalenol or DON, at or greater than 1 part per million. “Our goal is to be able to fine-tune it so we can differentiate between potential lower and higher levels of DON, but we’re not there yet,” Paul says. “We’re still early in learning how to manage ear molds and mycotoxins.”

CORN MOLD: This ear is infected with diplodia ear rot, which produces a light gray mold.

More mycotoxin answers

Paul’s work is already helping growers in vulnerable areas make better decisions about whether spraying fungicides will lower risk of ear mold and mycotoxin issues. But what else should you know today if you are concerned about ear rots, molds and mycotoxins?

Here is a sampling of questions and answers provided by the Crop Protection Network, a group of Extension specialists from land-grant universities working together to provide information.

What are mycotoxins? They are natural, nonliving compounds that fungi produce. Mycotoxins can have detrimental health effects to both humans and animals if they eat contaminated food or feed.

What mycotoxins occur in corn? There are five major ones:

WHICH DISEASE? Trichoderma ear rot can result in a bluish-green mold surrounding kernels if allowed to continue developing. It is more typically found in drier years with drought stress.

How do I scout for potential problems? Scout fields for ear rot diseases at black layer and just before harvest. Randomly select plants and pull back husks to examine ears. For example, check 20 ears from five different areas. If you find a diseased ear, examine 10 more ears from adjacent plants.

During your examination, ask three questions: What ear rot disease is present? How much of the ear is affected by ear rot? What proportion of the crop is affected?

When should I test for mycotoxins? Risk of mycotoxins in grain increases with number of infected kernels per ear. Assume that diseased kernels contain mycotoxins. However, mycotoxin levels may vary. Corn that appears to have a mild ear rot may still have very high mycotoxin levels.

If you find any ears with aspergillus ear rot, test harvested grain for aflatoxin. If 30% of ears have gibberella or fusarium ear rots, test for DON and fumonisins. Also test if you observe severe symptoms of either disease on multiple ears.

Will drying, heating, freezing or applying chemicals reduce mycotoxins in grain? No. However, reducing moisture content to below 15% quickly is a big help to minimize further mycotoxin accumulation after harvest. Dry grain to 13% for long-term storage.