Warm, wet conditions as the grain dries down favors the development of Ear Rot. It is important to scout your fields for moldy ears and if more than 10% of the ears presenting as ear rot to schedule a early harvest date to prevent further deterioration of grain.
Ear rots can reduce yield and quality of harvested grain. Some ear rot fungi may produce mycotoxins, which are harmful and can be fatal to livestock. Ear rots can continue to be a problem in storage if the grain is not stored under optimum conditions. Ear rots can be caused by several different fungi. Generally, ear rots are problematic in corn following corn fields and when the ears are damaged by insects. Kernel moisture above 18% favors the growth of all ear mold fungi.
Scouting for Ear Rot
Scouting during R5 to R6 stage of the corn
Check at least 100 ears selected throughout the entire field for Ear Rot
If more than 10% of the plants have an ear rot, harvest the field early
Dry and cool the harvested corn quickly
Test moldy grain for mycotoxins before feeding to livestock
Diplodia Ear Rot
Diplodia is the main ear rot that we should be on the look for right now. With a lot of rainfall in August and September and now cool, wet weather in September and October, Diplodia will be the favored Ear Rot. Diplodia Ear Rot is identified as a dense white mold beginning at the base of the ear but eventually will become grayish-brown and rots the entire ear. Mold may be apparent on the outside of the husk or on the shanks. There will also be raised black bumps on the mold of the husk and kernels.
Scouting Tips
Diplodia may be more prevalent in fields with infected corn residue such as corn followed by corn fields. The ear leaf of the ear will usually die prematurely on the infected ear making them easy to spot in the field.
Image 1: Diplodia Ear Rot Kernels. Image 2: Dense white mold on the corn ear.
Resources: ISU Extention & Outreach. ISU Integrated Crop Management.
