Thursday, October 1, 2009

Corn Yields may be Hurt by Fungi

Sam McNeill, Extension Agricultural Engineer and Paul Vincelli, Extension Plant Pathologist with the University of Kentucky College of Agriculture Cooperative Extension Service

USDA’s mid-September crop report predicted record level corn yields for Kentucky of 155 bushels per acre. Coupled with increased acreage, the state’s production could top 175 million bushels, which is also a record. However, a potential ‘fly in the ointment’ with this year’s crop is the delayed harvest coupled with damp weather which has led to stalk, ear and kernel rots. As noted in previous news stories, potential problems with field fungi (Diplodia, Gibberella, Fusarium, etc.) have lead to concerns about subsequent storage. While not all fungi produce mycotoxins, mold-damaged kernels are more susceptible to those that do. So it is best to err on the side of caution and check corn lots with field mold for mycotoxins before feeding to livestock.
When harvesting mold-damaged corn, adjust combines to minimize mechanical damage so that sound kernels are protected and to maximize cleaning, so that lightweight kernels are removed. Harvest, handle and store damaged corn separately when feasible and market early to reduce demands on storage management.

Grain moistures above 18-20% favor the growth of field fungi and the longer corn remains in the field the greater the chance of mycotoxin production. Thus, damaged corn should not be allowed to dry in the field to avoid drying costs. Corn with light damage should be dried to 15% within 24 hours after harvest and cooled to 40 degrees as soon as weather permits, in order to control mold growth during storage. This will create a storage environment within the grain mass that is below 65% humidity, which is dry enough to control mold growth and development (see values in the equilibrium moisture table). Corn with heavy to moderate damage should be dried to 13 to 14%, respectively, cooled as quickly as possible and moved before March.

The table below presents the equilibrium moisture contents for shelled yellow corn at different temperature and relative humidity conditions. Example: Corn that is 40 degrees and 13.7% moisture will create a relative humidity of 55% within the grain mass, which is safe for storage.

Relative Humidity
Corn Moisture, %

If mycotoxin problems are suspected, check with crop insurance providers to see if adjustments may be needed and how to account for the areas that are impacted. Insurance adjustments generally need to be made on standing corn at or before harvest.

The following publications provide more information on vomitoxin, aflatoxin and grain testing labs:

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