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C.O.R.N
Newsletter
2005-34
October 10, 2005 -
October 18, 2005
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Corn Ear Rot Problems in Ohio
by
Pierce Paul, Peter Thomison, Dennis Mills
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In a year when stalk quality has been badly affected by poor weather conditions (drought) and stalk rots, lodging of up to 90% is being reported in some cornfields. In addition to not being able to mechanically harvest ears on lodged corn plants, yield loss associated with lodging is further compounded by the fact that ears in contact with the ground often become moldy and develop ear rots, resulting in poor grain quality. While ear rots may be caused by several fungi, the most important ear rot problems in Ohio, Gibberella, Diplodia, and Fusarium ear rots, are caused by some of the same fungi associated with stalk rots, Gibberella zeae, Stenocarpella maydis and several Fusarium species. Hence, the most important sources of spores for infection of the ears are corn stalk and ear pieces left on the ground from a previous crop. Some ear rot-causing fungi also reside in the soil. Under wet conditions, spores are produced on debris on the soil surface and are usually wind-blown or rain-splashed to the ears. When lodging occurs, infection is greatly facilitated by the fact the ears are closer to or come into direct contact with the fungi on infected debris. In addition, infection is further favored by the fact that ears in contact with the grounds often remain moist. Moisture favors the development of ear rots.
Ear rots also occur on plants that are not lodged. During silking and early grain development when the ears are most susceptible to infection, the ear rot fungi usually penetrate the ear via the silk channel. Later in the season, however, infection mostly occurs at the base of the ear where the fungi penetrate the husk. Late season ear rot development is favored by rainfall prior to harvest, especially when the ears do not turn down and water collects at the base of the ear between the husks and the kernel. Poor growth conditions during the early part of this season may have prevented kernels from developing fully in some fields. Poorly developed ears (“beer can” ears) are more likely to remain upright than fully developed ears, and as a result, are more likely to develop ear rots. In addition, whether the ears turn down or remain upright varies from one hybrid to another. Given the rains we have had in some areas over the past few days, fields with poorly developed ears that do no turn down, hybrids with ears that dry in an upright position, and severe lodging may experience the greatest ear rot problems. For more information on ear rots consult the OSU Plant Pathology web site "Ohio Field Crop Diseases" at http://www.oardc.ohio-state.edu/ohiofieldcropdisease/.
With ear rot come the additional concerns of kernel rot and mycotoxin accumulation in storage. In addition to the physical damage caused by ear rots, some ear rot fungi produce mycotoxins that reduce the quality and value of the grain. Storage temperatures above 40F and kernel moisture content of 22% and above are favorable for the growth of toxin-producing ear rot fungi (Fusarium species). Growers are advised to follow certain harvest and storage guidelines to minimize problems associated with kernel rots and mycotoxin contamination:
1. Harvest fields with stalk rot problems early to minimize lodging, and consequently, ear rot development.
2. 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.
3. Dry harvested grain to 15% moisture and below to prevent further mold development in storage.
4. 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.
5. Periodically check grain for mold, insects, and temperature.
6. If mold is found, send a grain sample for a mycotoxin analysis to determine if toxins are present and at what level. Toxins are harmful to humans and livestock.
For more on moldy grain, mycotoxins, and mycotoxins sampling and analysis visit the following websites:
http://www.oardc.ohio-state.edu/ohiofieldcropdisease/wheat/mycotoxin%20text2.htm
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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