Ear rot is an issue that often doesn't develop or isn't noticed until the end of the season. These diseases can reduce test weight and nutrient values, but equally important, some of the fungi that cause these diseases can produce toxins.
Our most commons ear molds in Pennsylvania include Diplodia ear rot and Gibberella ear rot. We have also seen some Fusarium ear rot, which is less common for our growers.
Diplodia ear rot (see photo above)
- Color: white to grayish, with small black structures sometimes produced on husks, kernels, cobs
- Good to know: Tends to affect large portions or the entire cob. Overwinters in infected debris.
Gibberella ear rot
- Color: reddish, starts at tip and grows down ear
- Good to know: Can produce toxin (DON and others); associated stalk rot causes reddish-pink coloration inside stalk; caused by same fungus responsible for head scab in wheat; rotate to beans or other non-host next year.
What to do
Fields that are affected by ear molds are probably best harvested as soon as possible for grain. This is because the best way to stop fungal growth is to dry corn to 13% moisture or less (and less than 70°). This won't eliminate the mold or toxins already present, but will prevent further growth and toxin production in storage. The longer the crop is in the field, the more opportunity there is for mold to develop and spread.
Since ear corn continues to dry in cribs, it can be harvested at 21% moisture or lower. High moisture ear or shelled corn will heat up in storage and allow molds to spread quickly. Bird, insect or combine damaged kernels are also at higher risk for mold development in storage. If at all possible, try to clean out damaged kernels during harvesting and remove fines with a rotary cleaner. Keep good grain separate from highly contaminated grain and test for toxins. It may be possible to feed some of this to animals less sensitive to mycotoxins.
There is a great new resource for identifying and handling ear rots available at Crop Protection Network. Find guides about these diseases as well as critical information on how to deal with the possibility of mycotoxins.
These resources were created by pathologists across the continent so that they would be applicable to growers in all the major regions, including ours.