As harvest nears or progresses throughout Nebraska, stalk and ear rot diseases continue to become evident and producers should be monitoring for diseases.
Figure 1. A few ear rot diseases have developed in some corn fields, such as these from a field in Madison County.From Market Journal on YouTube
Stalk rot diseases have weakened stalk strength in some fields, resulting in lodging. Most of the corn is in very good condition; however, some fields have ears with one or more ear rot diseases, such as Diplodia, Fursarium, Gibberella or others (Figure 1). Ear rot diseases will likely continue to grow in storage which will adversely affect grain quality. Drying corn to less than 15% and cooling it will help to slow mold growth for short-term storage, but will not kill the fungi or prevent future growth in the bin.
Pay special attention to fields that have one or more risk factors for stalk or ear rot diseases and lodging:
Higher yielding hybrids
Lost leaf area (due to leaf diseases, hail, etc.)
Excessive rainfall/ponding anytime during the season
Stalk or ear wounding, usually by hail or insects
High planting populations
Tall plants
Thin stalks
If you are in doubt about the identity of a disease or cause of another plant problem, you can submit a sample to the UNL Plant and Pest Diagnostic Clinic (P&PDC) for diagnosis. For more information about these and other plant diseases or for submission forms for the P&PDC and submission instructions, visit the Clinic’s CropWatch website.
More details and photos of these and other diseases can be found in:
Figures 2a and b. Growth of beneficial fungi and their black spores on corn husks (a) (and other plant parts) may give it a dark, dusty appearance, especially during harvest. The ear underneath is usually unaffected by these fungi (b).
Many people have noted the appearance of black to gray discoloration or “dust” on corn plants during recent weeks. In some cases, large amounts of black “dust” has been reported from combines during harvest, sometimes looking like smoke. The large amount of microscopic spores produced by some fungi can cause these phenomena.
Diseases such as common smut have been common this year and could have contributed to the appearance of these spores. In addition, the late season rainfall has created a favorable environment for other common, beneficial fungi to flourish and rapidly produce copious amounts of spores. Some of these fungi, such as Alternaria spp., grow on dead plant tissue, like corn husks, but don’t typically cause damage to the ear underneath (Figures 2a and 2b). No management is necessary for this issue and it’s not expected to damage the corn, although dust masks may be advised for those who are prone to respiratory issues and sensitive to particulate matter.
Tamra Jackson-Ziems Extension Plant Pathologist
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