Aspergillus Ear Rot
Symptoms of Aspergillus Ear Rot
- 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
|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.
- 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
- 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.