Warm, wet conditions as grain dries down could favor the development of ear rots. In the eastern corn belt, corn pathologists report that Diplodia ear rot (Fig. 1) is prevalent (C.O.R.N. Newsletter; The Bulletin; and the Pest and Crop Newsletter). In Illinois, there are reports of grain being turned away from elevators because of poor quality due to Diplodia ear rot.
Figure 1. Diplodia ear rot is usually recognized by the dense, white mycelium that starts at the base of the ear and grows between the kernels.
Corn coming in to the Iowa State University Grain Quality Lab from field trials in central, northeast, and southeast Iowa has been affected by a variety of ear rot fungi, and many individual ears display symptoms of multiple fungi. Some of these ear rot diseases are capable of producing mycotoxins, which can result in marketing restrictions for affected grain. Unfortunately, the risk at this point is not generalizable—fumonisins, deoxynivalenol (vomitoxin), aflatoxin, and zearalenone are all potential suspects in locations throughout the state. Corn earworm injury was noted in central Iowa samples; these samples were also heavily impacted by ear rot fungi.
It is important to scout fields to determine if ear rots are a problem. If greater than 10 percent of the ears are moldy, fields should be scheduled for an early harvest to prevent further deterioration of grain. Dr. Charlie Hurburgh recently presented some tips for grain handling and storage.
Publications and training modules are available for those who would like to learn more. The Crop Protection Network recently posted publications on corn ear rots and mycotoxins that are available for download. Moreover, the Iowa Grain Quality Initiative has a training module describing mycotoxin development.
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