Corn ear rots and mycotoxins
Now is the time to begin scouting for corn ear molds. New corn disease management guides are available.
Corn disease management guides have been produced and are freely available for download as part of the Crop Protection Network, including:
- Ear Rots (CPN-1101)
- Mycotoxin FAQs (CPN-1102)
- Grain Sampling and Mycotoxin Testing (CPN-1103)
- Proper Storage for Mycotoxin-affected grain (CPN-1104)
- Using Atoxigenics to Manage Aflatoxin (CPN-1105)
Now is the time to begin scouting for corn ear molds at the late dent stage. Ideally, visit five points throughout the field and pull the husks all the way back on 20 ears, for 100 ears per field. Examine the entire ear for ear rot and use the corn disease guide to aid in diagnosis. If unable to identify the ear mold, a sample including the entire ear can be sent to Michigan State University Diagnostic Services.
Gibberella ear rot and Fusarium ear rot appear to be the primary ear rots of concern in Michigan, though others can and do occur. Insects can also play a role, including western bean cutworm, which can result in wounds for potential fungal infection. See the MSU Extension article “Check corn now for western bean cutworm damage before harvest” for more information.
Ear rots can be managed to reduce incidence and severity. Fields with a history of ear rot disease should be planted with hybrids that are less susceptible. Corn should be grown under conditions that promote healthy plants and insect damage should be minimized. Don’t rely on fungicides; although there are products that require a FIFRA Section 2(ee) for use, we need more information on fungicide efficacy.
Fields that are identified to have ear mold should be harvested early and the grain should be segregated. During harvest, combine adjustments can be made to discard lightweight diseased kernels. Grain moisture should be lowered as quickly as possible to less than 15 percent to minimize additional mycotoxin accumulation. For long-term storage, moisture should be brought down to less than 13 percent and cooled to 30 degrees Fahrenheit. Grain should be tested for mycotoxins when fields with ear rot problems are detected. For information on grain sampling and mycotoxins, see the Grain Sampling and Mycotoxin Testing guide.
I would appreciate observations on ear rot and mycotoxin levels, which can be emailed to me at firstname.lastname@example.org.
Check out the collaborative multi-university Crop Protection Network website for information on soybean and corn diseases.
Dr. Chilver’s work is funded in part by MSU’s AgBioResearch.