CORN Newsletter: 2009-33, September 29, 2009

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C.O.R.N Newsletter 2009-33
September 29, 2009 - October 5, 2009

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Corn Ear Rot and Potential Mycotoxin
by Pierce Paul, Dennis Mills


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We have had several reports of ear rot problems in corn. This disease is caused by one or more of several fungi capable of infecting, colonizing and damaging the ear. The most common members of the ear rot complex are Gibberella zeae (causes Gibberella ear rot), Stenocarpella maydis (causes Diplodia ear rot) and members of the genus Fusarium (causes Fusarium ear rot).

Gibberella ear rot, is the most common of the ear rots this year, however, we have also received reports of Diplodia ear rot in some fields. Diplodia causes a thick white mass of mold to grow on the ear, usually initiating from the base of the ear and growing toward the ear tip. Diplodia infections can begin before tassel emergence up to silking. With Gibberella ear rot, the fungus enters the ear tips through the silk channel. A visible white to pink mold covering the ear tip or more of the ears is characteristic of this disease. Gibberella ear rot is generally most severe when rain and wet weather is prevalent during the 7 to 10 days after silking.

The Gibberella ear rot fungus produces mycotoxins that are harmful to animals. These include deoxynivalenol (Vomitoxin) and zearalenone and T-2 toxin, all of which may cause health problems in livestock. Therefore, suspect grain should be tested for these mycotoxins by chemical analysis before being fed to animals. As a general rule do not feed any grain with 5% or more Gibberella moldy kernels. Hogs and young animals are particularly sensitive to these mycotoxins. Diplodia ear rot is less of a concern from a mycotoxin standpoint. There have been no reports of Diplodia producing mycotoxins that are harmful to animals in Ohio, but animals do refuse to eat grain with high levels of Diplodia-damaged kernels. Additionally, severely affected grain has low nutritional value.

Certain hybrids are more susceptible to one or more ear rots than others. Examine ears to determine the presence of ear molds. Make a note of which ear rots are present and hybrids that are most affected. Make future hybrid choices based on this information.

Growers are advised to follow certain harvest and storage guidelines to minimize problems associated with kernel rots and mycotoxin contamination:
1. Harvest at the correct moisture and adjust harvest equipment to minimize damage to kernels. Mold and mycotoxins tend to be higher in (machine or insect) damaged kernels.
2. Dry harvested grain to 15% moisture and below to prevent further mold development in storage.
3. Store dried grain at cool temperatures (36 to 44 F) in clean, dry bins. Moderate to high temperatures are favorable for fungal growth and toxin production.
4. Periodically check grain for mold, insects, and temperature.
5. If mold is found, send a grain sample for a mycotoxin analysis to determine if toxins are present and at what level. For more on moldy grain, mycotoxins, and mycotoxins sampling and analysis visit the following websites: http://www.oardc.ohio-state.edu/ohiofieldcropdisease/Mycotoxins/mycopagedefault.htm.

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868


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