What is corn mold?
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.
|Aspergillus||Gray-green or light green||Powdery mold starting at tip of ear||
Damaged silks or kernels typically from insects
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
|Usually begins at ear tip and progresses to the base||Infection favored by cool, wet weather after silking||
Vomotoxin, zearalenone; harmful
|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.