By Andy Michel, Pierce Paul
Although western bean cutworm (WBC) flight counts have been relatively stable compared to last year, several growers and extension educators have sent in pictures of western bean cutworm infestations and damage in corn. Obviously it is much too late to do much at this point, as the larvae are either still protected, or more likely, have dropped to the ground to overwinter. However, the holes and damage that remain could lead to secondary infestations from mold and fungi, and some of these infestations may also be a source for mycotoxins, including fumonisins and deoxynivalenol, AKA vomitoxin.
In some cases, damaged kernels will likely be colonized by opportunistic molds, meaning that the mold-causing fungi are just there because they gain easy access to the grain. However, in other cases, damaged ears may be colonized by fungi such as Fusarium, Gibberella and Aspergillus that produce harmful mycotoxins. Some molds that are associated with mycotoxins are easy to detect based on the color of the damaged areas. For instance reddish or pinkish molds are often cause by Gibberella zeae, a fungus know to be associated with several toxins, including vomitoxin. On the other hand, greenish molds may be caused by Aspergillus, which is known to be associated with aflatoxins, but not all green molds are caused by Aspergillus. The same can be said for whitish mold growth, some, but not all are caused by mycotoxin-producing fungi.
So, since it is not always easy to tell which mold is associated with which fungus or which fungus produces mycotoxins, the safe thing to do is to avoid feeding moldy grain to livestock. Mycotoxins are harmful to animals – some animals are more sensitive to vomitoxin while others are more sensitive to fumonisins, but it is quite possible that multiple toxins are present in those damaged ears. Mycotoxin-producing fungi are also opportunistic. If you have damaged ears and moldy grain, get it tested for mycotoxins before feeding to livestock, and if you absolutely have to use moldy grain, make sure it does not make up more than the recommended limit for the toxin detected and the animal being fed.