Ear Moulds in Corn

Not every growing season brings a high risk of ear moulds in corn, but it certainly can be an issue every once in a while. It is crucial to scout for ear moulds of all kinds every fall to determine risk and harvest order. Upright ears, tight husks, high humidity, precipitation and very slow drying conditions are all factors that contribute to mould development and spread. Severity and mould types will vary, so scouting is recommended, regardless of environmental potential.

There are several types of mould that can grow on corn, which raises a few concerns; first being yield. Yield can be affected simply by mould taking over several kernels and spreading throughout a cob. Affected kernels likely disintegrate or pass right through the combine at harvest. Kernels can be successfully harvested but cracked or damaged. Finally, harvest may be a total success, only to learn there are high mycotoxin levels (most concerning being vomitoxin or DON – Deoxynivalenol) in the grain, deeming it unsaleable. Husky Grain states that they buy grain with only a maximum level of 1 ppm of vomitoxin.

If a producer is unsure of their risk this year, the first step will be to scout their corn and identify any moulds occurring. Vomitoxins are primarily produced by Gibberella or Fusarium ear moulds, so if either of these are identified or suspected, the risk is increased. Mycotoxins cannot be identified visually, so a representative sample needs to be sent for analysis, if suspected. Samples in Manitoba can be sent locally to:

Central Testing Laboratory Ltd., Winnipeg

Gibberella Ear Mould

Figure 1: Gibberella Ear Mould

Fusarium Ear Rot

Figure 2: Fusarium Ear Rot

Ear Moulds OMAFRA

Figure 3: (L to R) Gibberella, Penicillium/Trichoderma and Diplodia Ear Rot. Photo Credit: Ontario Ministry of Agriculture, Food and Rural Affairs.

Fields with high incidence of moulds of any kind should be harvested first, where possible. Affected kernels should be harvested and dried as soon as possible to minimize spread and further degradation. High temperature drying (anything above 30oC) will stop mould growth and mycotoxin production but will not reduce mycotoxins already present. See OMAFRA’s article on Harvest Tips for Mouldy Corn for more information that may benefit corn harvest this year.

Corn Ear Mould Identification Article – Ontario Ministry of Agriculture, Food and Rural Affairs

Field Drydown

We are often quite fortunate with drying weather for natural grain dry down in the field. Manitoba Agriculture has an article indicating speed of natural drying in the field, in October and November. It also touches on artificial low temperature versus high temperature drying, estimating drying costs, in-storage cooling and much more. It is a great reference to bookmark.

More great articles on field dry down, natural air drying and storage of grain corn:

Successful Farming on 8 tips for long-term grain storage

Ken Hellevang, NDSU extension engineer – Grain Drying and Storage – Corn and Soybean

Bob Nielsen, Agronomy Department, Purdue University – Field Drydown of Mature Corn Grain

Manitoba Agriculture – Harvesting Grain Corn in Late Fall