The Indiana Certified Crop Adviser panel includes Betsy Bower, Purdue Extension senior research associate, West Lafayette; Abby Horlacher, Nickel Plate Consulting, Sheridan; Brian Mitchem, Farmer 1st Agronomy Consulting Services, Decatur; and Dan Quinn, Purdue Extension corn specialist, West Lafayette.

 

I noticed some sort of ear rot in one of my cornfields. Which ear rots and ear molds are prevalent this year? Is there anything I can do about it this late in the season?

 

Bower: Think back to the environmental conditions up to three weeks after pollination. If conditions have been exceptionally dry, aspergillus could be the prevalent ear rot, especially in sandy soils. If conditions are dry and insect feeding has occurred, then you could also see penicillium and trichoderma ear rots. If conditions are wet and humid during and up to three weeks after pollination, then gibberella, diplodia and fusarium ear rots could be more common.

 

For the most part, these ear rots can be distinguished from one another in the color of the mold and how they infect an area or kernel to kernel. Consult the Purdue Corn and Soybean Field Guide to see pictures and descriptions of each disease.

 

Most of the time, finding an infected ear here or there in a field will not present much of an overall problem, but if you are finding a lot of ears with mold in a field and are concerned about how the mold may affect harvest, send the ears to the Purdue Crop Diagnostic Center. For a nominal fee, you will be provided with info on all the diseases and other pests that have impacted the ear.

 

In the case of ear molds, there will likely be info on how to harvest and dry the grain to limit mycotoxin development. Gibberella, fusarium, aspergillus and penicillium have the potential to develop mycotoxins, which can lead to the docking of grain prices — if the grain can be sold at all.

 

Horlacher: At the time of writing this response, we do not have any ear rots or ear molds prevalent this year. We also still have a lot of fields waiting to tassel. When ear rots are present in the field, I recommend harvesting early and taking grain straight to the elevator. Do not store this seed.

 

Mitchem: Some of the most common ear molds are gibberella, fusarium, penicillium, diplodia and aspergillus.

 

Aspergillus is more common to the south, but we can periodically see the dry green mold typically on the tip of the ear. It can also be found lower on the ear.

 

Fusarium is a common ear mold that can be associated with insect and/or bird feeding. Damaged kernels around a wound can look anywhere from pink or purple to brown. A white streak called a starburst can also be an indication of fusarium. The starburst is commonly seen at the ear tip but can also move down the ear with favorable conditions. Fumonosins are produced, which are toxic at high levels to livestock.

 

Diplodia can be identified as a pasty white mold that can infect the entire ear. It causes lightweight kernels that have an off flavor for livestock but does not have a toxin associated with the disease in the U.S. The shuck will often stick to diseased kernels and have a gray appearance.

 

Gibberella is the most common and most concerning ear mold in the state. Two toxins are produced, deoxynivalenol, also called DON or vomitoxin, and zearalenone. These cause feed refusal and reproductive issues in animals. Gibberella is associated with cool, wet and/or humid conditions at silking. The disease can also increase in the fall with warm and moist conditions that will remain until a good frost.

 

Some fungicides have shown a reduction of DON levels in corn when applied at silking. Research done at Ohio State University in hybrid performance trials show good responses to products such as Miravis Neo and Delaro Complete. The research also shows that hybrid selection plays a major role in limiting DON levels in corn.

 

There are several things that can be done to limit DON levels in corn. First, harvest and dry to 15% as soon as possible. That will stop the mold growth. Next, try to remove as many fines as possible from grain storage. The removal of fines has been a major improvement for those that have experienced issues.

 

Quinn: Several different types of ear rots and ear molds can be observed in Indiana cornfields depending on the year and environment, with the most common concerns being gibberella, fusarium, aspergillus, penicillium and diplodia ear rots.

 

Among these, gibberella ear rot has been especially important in Indiana because it can produce the mycotoxin DON (vomitoxin), while aspergillus, fusarium and penicillium can produce aflatoxin, fumonisins and ochratoxins. These issues are often associated with environmental stress, delayed maturity, insect damage, excessive rainfall or delayed drydown prior to harvest.

 

Unfortunately, there is very little that can be done to stop ear rot development this late in the season once symptoms are present. Management at this point should focus on minimizing additional disease development and grain quality losses. Fields with significant ear rot should be prioritized for early harvest because leaving infected grain in the field longer can increase mold growth and mycotoxin contamination.

 

In addition, harvested grain should be dried quickly below 15% moisture and stored under cool, dry conditions to reduce further fungal growth. Adjusting combine settings to remove lightweight or damaged kernels may also help reduce contamination levels. If severe ear rot is suspected, grain testing for mycotoxins is strongly encouraged prior to storage or feeding.