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Corn Mold

What is corn mold?

Photo of moldy ear of corn on stalk

Above average rainfall and continuous wet weather can slow field corn dry-down and delay harvest.

In many cases, very high soil moisture can restrict combines or similar equipment from entering fields, and crops may remain unharvested longer than usual.

This situation leads to several problems, including encouraging the growth of corn ear mold and reducing grain quality. In some cases, these types of mold may also pose a risk of mycotoxin contamination, depending on what type of fungal growth dominates, and thereby, affecting the overall grade of the corn.

How do I identify corn mold?

Fungal species known to cause mold on corn are Trichoderma, Penicillium, Cladosporium, Stenocarpella (Diplodia), Fusarium, Gibberella and Aspergillus. However, only a few – Fusarium, Gibberella and Aspergillus– can produce mycotoxins. Thus, identifying which fungal pathogens are associated with ear rot becomes key to assessing if and for which mycotoxins a field is at risk.

Each mold is slightly different in color and may also vary in distribution on an ear, which may help identifying the most prevalent fungal pathogens.

   Ear Mold    Color    Appearance    Conditions    Myctoxin
  Aspergillus   Gray-green or light   green   Powdery mold starting   at tip of ear   Damaged silks or   kernels typically from   insects or hail;
  common in dry years		   Aflatoxin; toxic to   livestock and humans
  Cladosporium   Gray to black or very   dark green   Streaks scattered over   ear; can appear   powdery; able to rub   color of kernel surface   Infects kernels   damaged by frost,   insects or hail   No feeding toxicity
  Diplodia   White to gray; severe   infection can cause   entire ear to appear   brown   Usually begins at base   of year and develops   toward the tip; grows   between kernels; often   speck sized black,   fungal, fruiting bodies   (pycnidia) will form   on the husks and at
  the base of kernels		   Most often in reduced   tillage and continuous   corn   Some association with   diplodiosis in cattle and   sheep
  Fusarium   White to pink   Individual kernels with   fungal growth scattered   across ear and/or   kernels with starburst   pattern   Infection points include   kernel growth cracks   and ear damage from   insects; warm and dry   weather favors disease   development   Fumonisin; toxic to   livestock, particularly   horses
  Gibberella   Often bright pink;   varies from red to
  white		   Usually begins at ear   tip and progresses to   the base   Infection favored by   cool, wet weather after   silking   Vomotoxin,   zearalenone; harmful
  to livestock
  Penicillium   Blue to green   Grows on and between   kernels; powdery   Infects kernels   damaged by frost,   insects or hail   Not known to produce   mycotoxin
  Trichoderma   Green   Grows on husks and   kernels   Favored by insects to   mechanical damage to   ear   Not known to produce   mycotoxin

Samples can also be sent to the WVU Plant Diagnostic Clinic for identification of fungal pathogens associated with mold.

Should I harvest or use corn with mold present?

As some mold produces toxins that are harmful to humans and/or livestock, especially dairy cattle, harvest and use decisions should be made by considering the concentration and type of toxins present in the composite sample taken from a field.

Prior to harvest, growers should take a close look at ears for prevalence of mold. Ears that have been damaged by birds should be inspected more closely. If the presence of toxin-producing fungal pathogens are suspected, an assessment of toxin concentration is necessary.

In a situation where 50 to 60 percent of the ears are infected with toxin producing mold species, the grower may decide not to harvest the crop and dispose of it by burning it or deep plowing the soil.

The best sampling methods are to take a composite sample of at least 10 pounds from a moving grain stream, or take multiple probes in a grain cart or truck for a composite 10-pound sample.

A sub-sample of 100 grams can then be sent to labs (e.g. Alliance Analytical Lab #616-837-7670) for toxin concentration analysis. If toxins are present, it is possible that the grain might be fed to a less sensitive livestock, such as beef cattle, depending on the specific toxin and its concentration.

Grains should be dried immediately to 12 to 14 percent moisture to prevent further fungal growth and toxin development during transit or storage.

You can find more information about corn ear mold and mycotoxins here. 

Author:  Mahfuz Rahman, WVU Extension Specialist, Plant Pathology – Agriculture and Natural Resources 

Photo property of Mississippi State University Extension Service. Table adapted from Dekalb AgKnowledge Spotlight.