Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu
There have been a few reports of ear rots in some fields in Delaware and Maryland. The most common ear rot this season is Fusarium ear rot, which we have observed in trials at the Carvel Research Center in Georgetown, Delaware, and in variety trials in Middletown.
Fusarium ear rot tends to be more of a problem when conditions are dry and hot around flowering. Therefore, you may notice it more this year in dryland fields when compared to irrigated fields. Three species Fusarium are common throughout our corn: F. verticilloides, F. proliferatum, and F. graminearum . These fungi can produce mycotoxins under some conditions. Potential mycotoxins produced by Fusarium-ear-rotting-fungi include fumonisin, deoxynivelonol, and zereleone. Of these, fumonisins are the most important as they are known to cause equine leukoencephalomalacia, “blind staggers” in horses, pulmonary edema in swine, and have been linked to human esophageal cancers in other parts of the world.
Symptoms of Fusarium ear rot vary, but typically infected kernels are scattered throughout the ear. A white to pink fungal growth is sometimes observable on kernels and silks. Often, infected kernels have a starburst symptom, where fungal growth has damaged channels within the pericarp (Figure 1). The fungus overwinters in debris and produces spores under favorable conditions. Spores land on silks and grows into the ear as the silks senesce. Ears may also be infected through the shank or stalk. Insect and bird injury often enhances colonization of kernels.
Figure 1. Starbursting of corn kernels. This is a characteristic of infection by Fusarium spp. Photo www.aps.org. Photo by B.M. Anderson from the Compendium of Corn Diseases, 3rd Edition.
Affected corn harvested for silage or grain should be dried to below 15% moisture within 1-2 days of harvest to halt the production of mycotoxins. If you plan on storing the grain long term then it should be dried to 13% to decrease spoilage. Fusarium and other ear rotting fungi will continue to grow in higher moisture corn in bins.