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Molds, mycotoxins and storage keys to this year’s corn crop   PDF  Print  E-mail 
Posted by Susan Lillard  
Tuesday, 10 November 2009


Meeker County, MN - The cool summer with below average heat units followed by an extremely wet fall have caused great concern for a quality corn harvest in the fall of 2009. The wet and cool conditions have made for extremely favorable conditions for mold development on corn in the field. The higher moisture corn in the fields along with the presence should be concerns for livestock and non-livestock producers, but to what extent is going to be variable.

To better understand some of the problems with grain in many area fields it is important to understand what is potentially harmful. Molds are any of various fungi that often cause breakdown of organic matter. Mycotoxins are any of the mold-produced substances that may be injurious to vertebrates upon ingestion, inhalation, or skin contact. The other term that is often talked about is aflatoxoins. Aflatoxins are naturally occurring mycotoxins that are produced by some species of the fungus Aspergillus, most notably Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and among the most carcinogenic substances known.

Molds and mycotoxins can cause problems for livestock, but seeing some mold doesn’t necessarily make it a critical issue. Low levels of molds sometimes produce high levels of mycotoxins. High levels of mold sometimes produce insignificant levels of mycotoxins. Colors of mold can partly be an issue. Some of the colors of molds that are sometimes noticed include black and gray, white, and blue-green-pink. Aflatoxin in one of many mycotoxins and perhaps the most serious when present in feed for milk cows and in grain markets. Aflatoxin is more prevalent in a hot dry growing season like 1988 and is not likely to be an issue this fall.

One of the concerns at this point is for crop producers that have crop insurance coverage for molds. If farmers have questions about their crop insurance coverage or procedures they need to do they should be contacting their insurance provider so that they are under compliance. If the crop producer does not comply with what the crop insurance needs, it may not allow the farmer to take advantage of the crop insurance protection purchased. In essence, call your insurance provider if you have questions or concerns.

One of the first things to be doing in the case of the livestock or non-livestock producer is to evaluate the corn in the fields and to make decisions on whether certain fields and areas need to go into feeding a high moisture or dry corn rations, high temperature drying, or utilizing natural air drying systems. From my perspective and from talking with producers it appears that fields differ on the amount of mold showing from field to field. Reasoning for the differences can include differences in the moisture of the corn in the fields, tightness or lack of tightness of the husk to the ear, lodging issues, and corn resistance.

Corn that is dried to 14 percent moisture utilizing high temperature drying can stop further mold growth and mycotoxin development, but it will not eliminate the molds and mycotoxins that are already present. Essentially, removing the moisture stops further growth because molds need moisture to develop and release the mycotoxins. Corn that is dried utilizing natural air drying systems may not be the best management practice if there is a large amount of molds present because the moisture will be present for continued mold growth and mycotoxin development. If these systems are utilized hopefully the corn can get down below 14 percent in a fairly short period of time.

Corn that is put into storage as high moisture corn for the use of feeding livestock should also be looking at the best management practices for slowing and stopping mold and mycotoxin growth. Mike Rankin with the University of Wisconsin Extension posted an article recently reviewing moisture content for high moisture corn storage as rolled or chopped ear corn, or as shelled corn. Mike’s numbers are based on the moisture content of the grain. First for conventional top unloading silos, bunkers and silo bags: For ear corn products, Minimum 26, Ideal 32 to 36, Maximum 40. For shelled corn, Minimum 26, Ideal 28 to 32, Maximum 36. For Bottom unloading, Oxygen limiting silos: For rolled ear corn, Minimum 26, Ideal 28 to 32, Maximum 36. For Shelled corn, Minimum 24, Ideal 26 to 28, Maximum 32.

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