Cause Many fungi are associated with various ear rots and kernel rots of corn. In sweet corn, principal pathogens include Fusarium verticillioides, Penicillium oxalicum, Rhizopus stolonifer, Aspergillus spp., and Nigrospora oryzae. These fungi survive on plant debris in or on soil and may be found on seed. Ear rots are more severe following injuries, such as those from corn earworm, western bean cutworm, or heavy thrips infestation.
Symptoms Fusarium ear rot starts with a salmon-pink to reddish-brown discoloration of individual kernels or groups of kernels scattered over the ear. A powdery or cottony, pink, moldy growth develops later on infected kernels. Kernels develop whitish streaks on the pericarp if infected late in the season. Penicillium-infected kernels show green or bluish-green powdery, moldy growth. Rhizopus-infected ears show rough, whitish growth with black specks. Aspergillus ear rot appears as a black, greenish-yellow, or tan growth on infected areas of the ear. Nigrospora ear rot is not conspicuous until harvest when a shredding of the cob is noticeable. Kernels may have a grayish growth with black specks.
Cultural control
- Harvest early.
- Practice good insect control, especially for corn earworm, western bean cutworm, and thrips. See the PNW Insect Management Handbook for details.
- Plant resistant varieties and hybrids, if available.
- Store seed under proper conditions (below 18% moisture for ears, 15% for shelled grain) to prevent further growth of the pathogens.