Reports of ear feeding by western bean cutworm (WBC) have come in at a steady pace over the last few weeks. This is the 3rd consecutive year that we have seen a fair amount of feeding, some of it likely has led to an economic loss. The heaviest feeding has occurred in the Northwest and Northeast corners of Ohio. While it is too late to spray or control at this point (since most larvae are protected in the ear and are getting ready to pupate anyway), growers may need to watch for the development of ear rots. WBC can leave entry or exit holes in the corn husk, which can then provide a nice wound for pathogens like Fusarium and Gibberella. Some of these organisms can then be a further 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 for multiple toxins to be present in those damaged ears. 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. This link provides more information on ear molds and mycotoxin contamination: