Several questions are circulating around this year in regards to ear molds/kernel rots and potential for alfatoxin production in drought stressed fields. Here are a few details describing the specifics pertaining to aflatoxins.
Aflatoxins are a subgroup within a larger more general group called “mycotoxins”. Several ear rots and storage molds which occur every year to some degree are capable of producing mycotoxins. The term “mycotoxins” refers to “toxic chemicals” in a broad general spectrum including aflatoxins, fumonisins, tricothecenes, and zearalenone, some of which are much more problematic than others. Just because an ear and/or kernel mold is visually present does not necessarily confirm the presence of a mycotoxin or more specifically aflatoxin. Aflatoxins are a specific group of mycotoxins that get significant attention due to their potential to be relatively toxic to livestock and humans at varied levels. The specific B1 aflatoxin is also a known potent carcinogen which especially draws attention for regulation. Aflatoxins are produced by at least two species of Aspergillus. This kernel/ear mold is recognized by its somewhat olive green color. Although the presence of the mold indicates a higher risk of aflatoxin production, aflatoxins are not automatically produced when grain becomes moldy.
Environmental conditions will dictate if and at what level aflatoxins are produced. Problems associated with Aspergillus and aflatoxins are most common in hot, dry years (I think the summer of 2012 would fit that description). Fungi survive in plant residue from prior years. The fungi does best in corn from silking through grain fill when drought conditions are present during hot days and warm nights. The spores are carried by the wind and can enter the ears through injury caused by insect feeding, hail, drought, early frost and high wind which help to expose kernels to the fungus. In summary, if Aspergillus is readily evident within a field, aflatoxin production is definitely more likely considering the conditions we had this year. Those fields under high suspicion should likely be evaluated and managed separately. The following are some steps that can be taken to manage or reduce aflatoxins in grain:
1) Control ear-attacking insects.
2) Scout. Indentify early. If present, early harvest and drying of grain can help reduce further development.
3) Adjust combine to minimize kernel damage.
4) Clean grain bins and handling equipment.
5) Dry moldy corn immediately to 15% or less moisture when storing in the short term. Long term storage is not suggested.
6) Cool grain after drying and maintain at 35-40 degrees F through winter.
7) Control storage bin insects.
8) Check bins regularly.
Fig. 5.7 Yellow-green powdery growth of Aspergillus flavus on a corn rootworm-damaged corn ear can produce aflatoxins. Courtesy of Alison Robertson, Iowa State University.
The FDA has suggested recent exemptions to the long-standing action level of 20 ppb. They are as follows:
Human food and milk <0.5 ppb
Corn of unknown destination <20 ppb
Young animals <20 ppb
Dairy cattle <20 ppb
Breeding cattle, swine, and mature poultry <100 ppb
Finishing swine <200 ppb
Finishing cattle <300 ppb
Elevators will likely have their own testing protocols as well as tolerance levels depending on where the grain is being channeled to for end use.
Sources: Iowa State University
Hoegemeyer Hybrids Agronomy
Hopefully aflatoxins will not be a problem in your fields but be prepared and have a plan of action if you have concerns. If you have further questions, contact your local Hoegemeyer Agronomist of District Sales Manager.