Many different fungi can grow as mold in stored grain. Fusarium and Aspergillus are two of the most common fungi. Although not all fungi produce toxins, Aspergillus can produce aflatoxin which is carcinogenic. Livestock, poultry, and people are very sensitive to aflatoxins, and therefore the FDA has set allowable levels of aflatoxins very low (20 ppb).
Aspergillus fungi can infect the corn kernels through the silks and the infection is often favored during periods of hot weather and high humidity. Below normal soil moisture conditions has also been found to increase the number of Aspergillus spores in the air. Therefore, when drought stress and/or other stresses occur during pollination, the increased inoculum load (spores in the air), greatly increases the chances of infection. Often, Aspergillus will grow on the unfilled portions of the ear.
Time of harvest can be important in influencing the occurrence and levels of aflatoxin because Aspergillus does not compete well with other molds when corn is above the 20% moisture content. Therefore harvesting corn when moisture content is above 20% followed by rapid drying to at least a moisture content of 14% within 24-48 hours of harvest keeps further Aspergillus growth and toxin production at a minimum.
Mature corn that remains in the field or corn that is stored without adequate drying can be subject to Aspergillus growth and aflatoxin production. Temperatures between 80F and 100F and relative humidity of 85% are optimum for growth of Aspergillus. Growth of this fungus is poor below 55F, but if the grain is moist enough, toxins can still be produced. Reducing the moisture will prevent further mold from growing but it will not kill molds that are already present in the grain. If moisture levels should rise again above 12%, mold growth and toxin production will resume.
Damaged kernels are more likely to become infected with molds both in the field and in storage. Corn hybrids with good husk coverage and insect resistance traits are less likely to become infected with toxin producing fungi as a result of reduced kernel damage.
During harvest there are a few strategies which may help to reduce potential for aflatoxin. Producers can harvest early and dry immediately, avoid damaging kernels, store corn at 12% and keep storage and feeding facilities clean. For more information on aflatoxins in corn refer to http://igrow.org/agronomy/drought/.
Hollistic Resource Management:
We have been considering hosting a Holistic Resource Management Class in Pierre this winter. Holistic Management is a Decision-Making process that helps individuals or groups identify what they want and then achieve it. Holistic Management can also be viewed as a process to sort out and make sense of all the tools and choices we face each day. Decisions made within this framework take into consideration all social, financial, and environmental impacts. The class is targeted to ranchers and farmers.
Give us a call if you are interested in attending this class if it is held in Pierre. The SDSU Pierre Regional Center phone no. is 605-773-8120. For more information on the class visit; .