Aspergillus ear rot

Aspergillus ear rot is one of the most important diseases in corn. This fungi causes a mycotoxin called aflatoxin inside diseased corn kernels. A mycotoxin is a toxin caused by the organism living within the corn kernels.

Aflatoxin is the particular toxin that is produced by the fungus Aspergillus flavus which causes Aspergillus ear rot. The presence of aflatoxin affects the marketability and quality of corn. If the grain is consumed by livestock it can have serious health effects on those animals. The fungi love summers that are hot and dry. Aspergillus ear rot also is helped along by ear damaging insects. Insect damage offers a place for the spores to come into the ear, germinate, and infect the ear. Scouting is the first step in determining if you have Aspergillus ear rot or not. You should take at least 10 ears from several locations in the fields. Do no less than 30 ears. Especially take ears from dry areas in the field and look for plants that may have small or stunted ears. You are looking for an olive green mold on the ears. It will appear powdery like dust. Most of the time symptoms are found at the top of the ear. You may find other molds on the ears as you scout the fields, but the olive green mold is diagnostic for Aspergillus ear rot. If you think you have it you should get conformation from the Purdue Plant and Pest Diagnostic Lab at www.ppdl.purdue.edu

If you take infected grain to the grain elevator they may do some testing to determine if you have aflatoxin. The initial screening is through the use of a black light. How this works is some of the grain is cracked and exposed to the light. If the any of the kernels glow green-yellow it is presumed that the crop is infected with Aspergillus flavus and may contain aflatoxin. This test does not confirm the presence of aflatoxin, only a chemical test can determine if aflatoxin is present.

Minimizing economic loss can be difficult if aflatoxin is present in the grain. Areas of the field that are known to have Aspergillus ear rot should be avoided during harvest if possible. Fields known to have extensive Aspergillus ear tot should be harvested as early as possible because this fungus can still produce aflatoxin with the grain at 18 percent moisture. Rains can also contribute to aflatoxin contamination. The grain needs to be dried to below five percent to prevent any more fungal growth.

Managing for the reduction of Aspergillus ear rot is difficult as there are not corn hybrids that are resistant to infection. Avoiding stress is the best strategy for reducing Aspergillus ear rot. Plant hybrids that are tolerant to water, stress, and heat. Irrigation can also help reduce stress on the plants. Providing adequate nitrogen fertilizer and maintaining fertility will give your crop the best chance against Aspergillus ear rot. Good management and good scouting can help lessen the impact of Aspergillus ear rot on your yield and grain quality.

For more information contact Ann Delchambre at adelchambre@purdue.edu or phone 765-653-8411

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