Aspergillus Ear Rot

Symptoms of Aspergillus Ear Rot

Aspergillus Ear Rot on corn
  • Gray-green, olive, yellow-green or yellow-brown powdery mold growth on and between kernels.
  • Surface mold can develop anywhere on the ear.
  • Symptoms are often found at damaged areas of ear

Facts on Aspergillus Ear Rot

Aspergillus infection at hail wound in corn husk
Note Aspergillus infection at hail wound in husk.
  • Fungal disease caused by Aspergillus flavus and Aspergillus parasiticus.
  • 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 primary 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.
  • Circumstances that favor mold growth may also favor mycotoxin production although mold growth can occur with little or no mycotoxin production.
  • Aflatoxins, produced by A. flavus and A. parasiticus, are the only mycotoxins for which the U.S. Food and Drug Administration (FDA) has established formal action levels.
  • Corn grain with aflatoxins above 20 parts per billion (ppb) may not be sold for transport across state lines.
  • Aflatoxins normally contaminate few kernels (but concentrations in individual kernels is often very high) so sampling and testing is variable.

Disease Cycle

  • Aspergillus fungal spores are produced on crop residue on the soil surface and on discarded kernels and fines around grain bins.
  • Fungal spores become airborne and can infect kernels by growing down the silk channel when silks are yellow-brown and still moist.
  • Infection is most common through kernel wounds caused by several types of insects.
  • Aspergillus can occur on many types of organic material, including forages, cereal grains, food and feed products and decaying vegetation.
  • Partially or completely burying infected residue reduces disease inoculum and incidence.
  • Fungal spores overwinter on plant residue.
  • Aspergillus can also produce specialized survival structures that enable it to survive in the soil for extended periods.

Impact on Crop

  • When Aspergillus occurs, crop yield has normally been reduced by drought stress. Fungus 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.

Management of Aspergillus Ear Rot

Aspergillus mold growth on ear of corn
  • Plant regionally adapted hybrids.
  • Hybrids containing a Bt gene for above-ground insect protection help reduce damaged kernels and fungal spore entry points.
  • Little native hybrid resistance exists and seed companies do not rate hybrids for Aspergillus.
  • Hybrids that perform well in drought conditions generally have lower Aspergillus concentrations than hybrids that yield poorly in drought conditions.
  • Use a balanced fertility program designed for optimum yields.
  • Select planting dates appropriate for the area.
  • Limit damage from ear feeding insects by using appropriate field treatments.

    Harvest and Storage

    Proper storing, drying and maintaining grain quality will minimize problems.

    • Clean bins, areas around bins and all grain handling equipment before putting grain in storage.
    • 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 dispose of properly.
    • Aerate grain to equalized temperatures throughout the grain mass.
    • When using in-bin drying system, limit grain depth to quickly dry corn.
    • Protect stored grain from insects.
    • Check stored grain regularly and aerate to maintain low moisture and proper temperatures.
    • Hot spots need to be eliminated by stirring and cooling or removing grain from the bin.