NPIPM:Ear rots
Authors: Byamukama, E. and Yabwalo, D.
Causal Organisms
Several pathogens cause corn stalk rots:
Gibberella ear rot - Gibberella zeae
Fusarium ear rot - Fusarium spp.
Diplodia ear rot - Diplodia maydis (also known as Stenocarpella maydis)
Aspergillus ear rot - Aspergillus flavus, A. parasticus
Penicillium ear rot - Penicillium spp
Symptoms and Signs
Corn ear rot symptoms comprise of rotting and discoloration of corn kernels on the cob. Corn ear rots may differentiated by the color associated with infected kernels. Gibberella ear rot also called red rot is characterized by reddish-pinkish color of infected ears. Infection may start at the tip of the ear and may grow down the ear. Sometimes infected ears have tight husks adhering to the ear. Fusarium ear rot symptoms include scattered kernels on the ear with whitish – lavender fungal growth. Diplodia ear rot typical symptom is bleached straw colored husks and a dead ear leaf. Infected ears usually have the rotting starting from the base of the cob. Corn ears with Aspergillus ear rot have infected kernels covered with masses of live to green spores. This ear rot is common on kernels with injury, however, the Aspergillus fungus can be on kernels without obvious symptoms. Penicillium ear rot causes kernels to appear bleached with blue-green powdery mold between kernels
Disease Impacts
Corn ear rots cause yield loss mainly through negatively impacting grain quality. With the exception of Diplodia ear rot, the rest of the ear rot fungi also produce mycotoxins which are toxic when consumed in grain. These mycotoxins affect marketability of the grain.
Life Cycle and Epidemiology
Ear rot pathogens overwinter on corn residue and in soil. Gibberella ear rot is favored by cool wet weather when corn is at silking growth stage. Fusarium ear rot fungus infects through the silk and wounds created by insect or bird feeding and hail injury. Diplodia ear rot develops under wet and warm weather conditions and corn is more susceptible after flowering as the silk dies off. Aspergillus ear rot develops under hot, dry weather. The fungus is spread by insects and wind and infection is increased by kernel injury.
Management Approaches
• Select resistant hybrids
• Practice crop rotation to manage corn residue
• Reduce plant stress through balanced soil fertility, planting appropriate planting rates
• Control insect pests to reduce injury
• Store infected grain separately to avoid contamination of the grain in the bin
• Grain should be dried to <15% moisture to avoid grain spoilage while in storage.
Other Online Resources
Crop Protection Network. Ear rots. https://cropprotectionnetwork.org/encyclopedia/corn-disease-management/ear-rots-2/
