Managing Mycotoxins in Corn: Harvest and Storage Tips

Dealing with mycotoxins in corn during harvest can be double trouble for farmers. Not only do they reduce yields and grain quality, but if contaminated grain is fed to livestock, it can lead to illness, reduced productivity, and even long-term health issues, hurting both animal performance and your bottom line.

These toxic compounds are produced by several ear rot molds that grow on corn. Even if they aren’t obvious on the corn being harvested, they can later develop on grain kernels in storage. However, managing the damage caused by ear rots and mycotoxins in corn begins with several decisions made before harvest.

Let’s walk through a few practical steps to protect your corn crop and your profits from the costly impact of mycotoxins.

Strategies to limit ear rot yield loss and mycotoxins in corn

Early harvest to reduce mycotoxins in corn

The longer you allow mycotoxins to develop in the field, the more challenging they will be in storage. Whenever you start to see visible signs of ear rot on your corn, it’s time to harvest those affected areas. Ear rots will typically stop growing when the moisture content of your grain drops below 12 to 13%.1

By harvesting your corn early, when moisture levels are still high (above 22%), you may be able to reduce the risk of mycotoxins in corn. Some institutions recommend harvesting corn at even higher moisture levels, around 28 to 30%, to reduce mycotoxin exposure by several weeks.2

However, if you decide to harvest at a high moisture level instead of letting the corn dry naturally, be prepared to immediately dry down your corn after harvest. Doing so will reduce moisture levels to below the ideal conditions for fungal growth, allowing for a better quality of your stored grain.

Adjust combine settings to avoid mycotoxins in corn

Your combine settings can make a huge difference when it comes to minimizing mycotoxin contamination at harvest. When ear rot is present in the field, the goal is to minimize kernel damage and separate as much lightweight, mold-infected material as possible.

You can achieve this by starting with the concaves and adjusting the rotor speed. Adjust the concave clearance to match the diameter of the average ear. Also, keep the rotor speed as low as possible while still effectively threshing the grain. Excessive speed tends to crack or break kernels, increasing the amount of fine particles in your grain. Be sure to double-check your clearance settings any time you switch concaves.

Then, once your threshing settings are correct, you’ll want to ensure that your cleaning system is also properly set up. Increase the fan speed to remove lightweight, mold-infected kernels, fines, and dust. This helps reduce the overall mycotoxin load in the harvested grain. Additionally, open your bottom sieve all the way to allow maximum airflow to the top sieve. Start with a 5/8-inch opening on the front and middle sections. Adjust as needed to balance grain cleanliness and loss.

Some producers have had success with perforated screens installed under the augers and elevator doors. These screens let fines fall through before they reach the bin. Research shows that this step alone can reduce some types of mycotoxin levels by as much as 40%, especially when grain is harvested at a moisture level below 25%.3 That said, drier corn is also more prone to cracking, so handle grain gently during unloading and storage to avoid creating more damaged kernels.

Quick drying at high temperatures to prevent storage mycotoxins

If you are harvesting corn with a high moisture level, you’ll need to immediately dry the grain down to less than 13%. This will stop fungi from growing or producing mycotoxins. If you’re seeing a significant amount of ear rot in your corn, consider storing grain at lower than 44 F.4

To dry your corn quickly, you’ll need to expose it to high-temperature drying conditions. This is typically at 140 to 200 F, which will accelerate the drying to adequate levels. Slow drying over a longer period of time could actually encourage fungal growth.5

While grain should always be stored in dry, sanitized bins, contaminated grain should never be stored for longer than a year, especially in warm spring or summer temperatures.

By adjusting combine settings, drying efficiently, and handling grain with care, you’re not only protecting your crop but also protecting your bottom line. A few proactive steps now can make all the difference when it’s time to store or sell.

Experts are available to help you make your harvest and grain storage decisions. Reach out to your seed retailer, a local extension office agent, or a seed company professional, such as your regional BASF representative.

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Endnotes

1. Sumner, Paul E., and Dewey Lee. “Reducing Aflatoxin in Corn During Harvest and Storage.” University of Georgia Cooperative Extension, July. 2024, https://secure.caes.uga.edu/extension/publications/files/pdf/B%201231_5.PDF.
2. Sumner and Lee. “Reducing Aflatoxin in Corn During Harvest and Storage.”
3. Hartschuh, Jason, and Pierce Paul. “Harvesting and Handling Ear Rot-Affected Corn.” Ohio State University Extension: C.O.R.N. Newsletter, vol. 2022, no. 34, 2022, https://agcrops.osu.edu/newsletter/corn-newsletter/2022-34/harvesting-and-handling-ear-rot-affected-corn.
4. Paul, Pierce. “Gibberella Ear Rot and Vomitoxin in Corn” Ohio State University Extension: C.O.R.N. Newsletter, vol. 2021, no. 02, 2021, https://agcrops.osu.edu/newsletter/corn-newsletter/2021-02/gibberella-ear-rot-and-vomitoxin-corn
5. Sumner and Lee. “Reducing Aflatoxin in Corn During Harvest and Storage.”