Corn Ear Rot Prevention and Management
There are many kinds of corn ear rots that cause significant damage to corn. Altogether, 79 million bushels of corn were impacted by corn ear rot in 2024. Not only will they reduce yields and grain quality, but they can harbor dangerous toxins that are unsafe for animal and human consumption.
To reduce losses and protect grain quality, ear rot management must be approached as a season-long strategy. Let’s explore several practices based on crop stage that help minimize the risk of fungal infections and improve outcomes.
Pre-planting corn ear rot management practices
Residue management
Since corn ear rot fungi live exclusively on corn, getting rid of corn stalks and plant residue on the soil is critical before planting corn again. Burying stalks and debris through deep tillage is more effective than surface burning, which often leaves infected material behind.
Crop rotation
Rotating away from corn for two to three years helps break the fungal life cycle and reduces overall disease pressure. It also lowers insect pressure. Insect damage often creates entry points for infection. Research recommends a three-year rotation over a two-year rotation to avoid any corn ear rot infections.
Hybrid selection
The right hybrid can make or break your harvest when it comes to corn ear rot. Choose hybrids with good resistance to ear rot pathogens and insects. This limits fungal entry and protects ears during critical periods of moisture and insect activity. Also, consider hybrids with Bt proteins that can protect against corn earworms and corn borers.
Planting corn ear rot management practices
Planting date
When you plant and how much you plant can impact the microclimate under the corn canopy. For silage corn, the earlier, the better. Early planted corn is more likely to escape various types of worm damage and ear rot pressure than later-planted corn. Planting in late April to early May helps the crop avoid peak periods of heat, humidity, and insect activity.
Plant population
High seeding rates can lead to a dense canopy that holds moisture and creates a favorable environment for both insects and fungal pathogens. This increases the chances of feeding damage and infection. Optimal seeding rate decisions should be made based on field conditions and hybrid choice.
Growing season corn ear rot management practices
Scout for ear rots
Scouting before or at the late dent stage, around R5, can help you determine what kind of treatment might be needed.
To determine if you have a problem, go to five different areas in your cornfield and pull the husks off of 10-20 ears. Look at the entire ear for mold and insect damage. Identifying the type of ear rot can also be beneficial. If you do find ear rot, you should send it off to be tested for mycotoxins. Mycotoxins in your harvested grain can make your grain unmarketable.
Fungicide applications
Fungicides can reduce ear rot severity, but timing is critical. Several studies have shown that fungicide treatment at R1 won’t have any effect on yield, but it can significantly reduce mycotoxins in your grain.
If insect pressure is high and causing damage to ears, fungicide treatments will be less effective. An insecticide to address the insect damage is the better option.
Alpha-cypermethrin is labeled for corn ear worm, European corn borer, and other insects that can damage corn husks, silk, or kernels.
Harvest corn ear rot management practices
Harvest early
When you’re scouting your fields close to harvest, if you start seeing 10% of your ears with rot, then plan on harvesting as soon as possible to prevent further fungal growth. If your fields are heavily infested, it may be best to harvest the corn when it’s above its optimal moisture level and then dry it down to 15% moisture. This will stop any further fungal growth.
You may also want to harvest heavily infested areas of your fields last, so you don’t mix your better grain with the contaminated grain.
Combine adjustments
Corn kernels infested with corn ear rot will usually be lighter than healthy corn kernels. You can take advantage of that at harvest time by making sure your combine settings are dialed in to remove as many damaged or lightweight kernels as possible. Adjusting fan speed and sieve settings can help clean up the grain and lower the chances of storing infected material.
Post-harvest corn ear rot management practices
Grain testing
If you saw signs of ear rot in the field, it’s smart to get your grain tested for mycotoxins before feeding or selling it. Even if the grain looks clean, it might still carry toxin levels high enough to be a problem. A lab test is the only way you can know if you have significant levels of harmful ear rot or mycotoxins in your stored grain.
Grain drying
Ear rot will continue to grow unless the moisture levels in the kernel are below 15%. Drying corn to this level will minimize ear rot spread throughout stored grain. If you plan to hold your grain for a long period, drying it below 12-13% and storing it at 30 F is often recommended. However, never store infected grain for more than a year.
Thoroughly clean equipment
Before you put anything into storage, make sure bins, augers, and dryers are cleaned out. Leftover kernels or dust from a previous batch can carry fungi and kick off a new round of contamination. Additionally, don’t let water runoff from your equipment infect your clean fields.
With proper scouting, timely fungicide and insecticide applications, and post-harvest precautions, each step helps reduce your risk, protect your grain quality, and avoid costly mycotoxin issues.
source：agweb
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