Production Blog

JEFFERSON CITY, Mo. (DTN) -- Farmers in the northern and eastern Corn Belt still need to consider Gibberella ear rot as harvest approaches, even as a warm and dry start to September may have moderated their concerns.

On a recent webinar hosted by Pioneer, agronomist Ryan Terry said that as conditions exist now, growers across the Great Lakes region should expect a much better harvest and much better grain quality in 2024 than in 2023.

"If you think back to last year, it was a cooler year that turned into a cool, wet fall that really delayed drydown in our corn crop," he said. "We had pretty widespread incidences of Gibberella in the whole Eastern Corn Belt, which resulted in really high vomitoxin levels in our grain and was a significant issue.

"This year, in general, we've had a warmer summer, and all indications are we're going to have a much drier, warmer weather pattern," he continued. "That should push grain maturity along and increase the drydown to reduce the amount and spread of the Gibberella."

GETTING 'GIBBY' WITH IT

Gibberella ear rot, or Gib ear rot, is caused by the mycotoxigenic fungus, Gibberella zeae (Fusarium graminearum) -- the same pathogen that causes Fusarium head blight (scab) in wheat. Found across the northern and eastern Corn Belt, it can produce two mycotoxins in the infected kernels: deoxynivalenol and zearalenone, which can cause health issues if present in livestock feed above certain threshold levels.

The fungus overwinters on crop residue, leading to infection during corn silking. Silks are most susceptible two to six days after emergence; ear rot is more prevalent when cool, wet weather occurs during the first 21 days after silking. Extended periods of rain in the fall, which delay dry down, can increase the disease's severity.

According to Peter Horevaj, North America field pathology lead for Corteva Agriscience, Gib ear rot has more than 45 known host plant species. Its occurrence incidence can increase in fields where corn follows corn or where corn follows wheat affected by Fusarium head blight.

The fungus can be identified most readily by the red or pink color of the mold. It almost always begins at the tip of the ear, and excessive mold may cause silks and husks to adhere to the ear. In severe cases, the pink mold is visible on the outside of the husks at the ear tip.

MANAGING MYCOTOXINS

The Crop Protection Network advises that corn should be scouted prior to physiological maturity to identify areas with mold problems. If greater than 10% of the corn sampled are moldy, the field should be scheduled for an early harvest to prevent further mold development. Grain should be cooled, dried and cleaned immediately after harvest. It should also be stored apart from grain harvested from healthy fields.

During the Pioneer webinar, product manager Jerron Schmoll said that while fungicide products are available that can provide effective protection from infection, the application window is very narrow.

"You're trying to control that silk channel infection, so timing is super critical," he said. "Even if you have perfect emergence, the odds of everything silking at exactly the same time so that you can catch that window is going to be difficult."

Schmoll noted that when harvesting, it's important that combine settings are dialed in to prevent infected kernels from ending up in the grain tank.

"Those infected kernels are going to be lighter weight, so getting those out of the back of the combine is going to be really important," he said, advising the same for "fines," ground-up kernel and cob tissue that tends to have higher mycotoxin concentrations than intact grain. He also emphasized reducing grain moisture.

"You've got to get the grain dry -- sub-15% -- as fast as you can. That's going to stop the growth of the fungus," said Pioneer product manager Jerron Schmoll during the webinar. "And don't store it any longer than necessary. You can see mycotoxins increase in stored grain, but they're not going to go down."

To manage Gibberella incidence in a field, Terry and Schmoll recommended rotating to a non-host crop such as soybeans and using tillage to bury infected crop debris. They also advised growers to select corn hybrids that express genetic resistance to the fungus.

Go here to watch Pioneer's full-length webinar on Gibberella ear rot: https://www.pioneer.com/….

Purdue University Extension offers an online publication discussing Gibberella ear rot here: https://www.extension.purdue.edu/….

The Crop Protection Network offers this overview of several ear rot diseases: https://cropprotectionnetwork.org/….

Jason Jenkins can be reached at jason.jenkins@dtn.com

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