Aspergillus Ear Rot

Written by Mark Jeschke

Disease Facts

  • Aspergillus ear rot is a fungal disease most commonly caused by Aspergillus flavus although it can be associated with other Aspergillus species.
  • Aspergillus ear rot is most common under drought conditions, high temperatures (80-100°F) and high relative humidity (85%) during pollination and grain fill.
  • Disease and associated aflatoxins are a common problem in the southeastern United States and Texas but less common and detrimental in the Corn Belt.
  • Corn ears damaged by insects or weather such as hail, high winds or early frost that cracks the kernels may predispose grain to infection (Figure 1).
  • Aspergillus fungal spores are produced on crop residue in fields and on discarded kernels and fines around grain bins.
  • Infection most commonly occurs via kernel wounds or insect damage but fungal spores can also infect kernels by growing down the silk channel when silks are yellow-brown and still moist.
  • Aspergillus can occur on many types of organic material, including forages, cereal grains, food and feed products and decaying vegetation.

 

Photo - Aspergillus infection on corn ear following hail injury.

Figure 1. Aspergillus infection following hail injury.

Symptoms

  • Gray-green, olive, yellow-green or yellow-brown powdery mold growth on and between kernels (Figure 2).
  • Infection often occurs at the tips of ears but can develop  anywhere on the ear, particularly if the ear has experienced physical injury or insect damage.
  • Fungal spores are powdery and may disperse when the husk is pulled back from the ear.

Mycotoxins

  • Aflatoxins, produced by A. flavus and A. parasiticus, are the only mycotoxins for which the U.S. FDA has established formal action levels (Table 1).
  • Corn grain with aflatoxins above 20 parts per billion (ppb) may not be sold for transport across state lines.
  • Mycotoxin levels can vary among infected ears and do not necessarily correlate to the severity of visible infection.
  • If Aspergillus ear rot is present in a field, the harvested grain should be tested for aflatoxin.

 

Photo - Corn ear showing Aspergillus ear rot symptoms.

Figure 2. Corn ear with aspergillus ear mold. A laboratory test for aflatoxin is recommended where Aspergillus ear rot is suspected.

Management

  • When Aspergillus occurs, crop yield has likely already been reduced by drought stress. Fungal infection may further reduce weight of infected kernels.
  • Production of aflatoxin by fungus is variable, but more likely under heat and drought stress.
  • If Aspergillus is confirmed, the corn must be tested to determine if aflatoxin is present and to determine the proper marketing channel.
  • Blending corn lots to reduce the level of aflatoxins is prohibited for interstate trade.
  • There is no method to “detoxify” infected corn.
  • Aflatoxins are not destroyed by fermentation and will be concentrated in dry distillers grain.
  • Since the disease enters the ear primarily through injury and insect feeding, hybrids with one or more aboveground insect protection traits can have a lower risk of Aspergillus ear rot.
  • Little native hybrid resistance exists and seed companies do not rate hybrids for Aspergillus.
  • Hybrids that perform well in drought conditions can have lower risk for Aspergillus infection than less drought-tolerant hybrids.
Photo - Corn ear tip showing aspergillus ear mold.

Figure 3. Corn ear with aspergillus ear mold.

Photo - Corn ear showing aspergillus ear mold symptoms - closeup

Figure 4. Corn ear with aspergillus ear mold.

Harvest and Storage

  • Clean bins, areas around bins and all grain handling equipment before putting grain in storage.
  • Infected fields or areas should be harvested as early as possible since the fungus will continue to develop and produce aflatoxin as the corn dries down. Begin harvest when grain is at 25% moisture and dry to 15% or lower within 24 to 48 hours.
  • Corn going into long-term storage should be dried to below 13% moisture and cooled to 30°F.
  • Adjust combine to minimize trash and broken kernels.
  • Harvest and store grain from Aspergillus-contaminated fields separately.
  • Clean grain going into storage by screening or gravity separator to remove lightweight and broken kernels, foreign material and fines.
  • High concentrations of aflatoxin may be found in corn screenings so they should be disposed of properly.

Table 1. U.S. FDA action levels for aflatoxin contaminated corn.

Table - FDA action levels for aflatoxin contaminated corn.


The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.