Update from the Field: Ear Comes Trouble!
Posted by David Dyson, Agronomist on September 25, 2017
Dave Dyson is a regional agronomist for The Andersons’ Farm Centers which are located throughout Ohio, Michigan, and Indiana. He is an Indiana native and grew up on a dairy farm in Miami County. A graduate of Purdue University with a degree in Crop & Soil Science, Dave has a deep knowledge of various agronomic topics and is committed to helping growers improve their crops. If you have any questions, Dave can be reached at david_dyson@andersonsinc.com.
The wacky weather we have experienced this year can lead to end of season diseases. Corn ear rot can be very devastating as corn with high levels of mycotoxins is harvested, but cannot be sold or used as feed. The three ear rots that are most common in northern Indiana, Michigan, and northern Ohio, are Diplodia, Gibberella, and Fusarium. The fungi that cause Gibberella and Fusarium ear rots can produce mycotoxins that are toxic to humans and livestock. Mycotoxins are not usually associated with Diplodia ear rots in the United States. Diplodia may not be toxic for feed, but it will destroy the quality of the corn. The damage that comes with Diplodia can also create a pathway for Gibberella and Fusarium.
Gibberella ear rot (figure 1) is caused by the fungus Gibberella zeae. This fungus over-winters on corn and wheat residue. When the weather is wet and cool during corn silking, the fungus will produce spores that will infect the corn ear. If the weather stays wet for several weeks after silking begins, the fungus will be able to create a foothold in the ear, causing problems during harvest. Gibberella can be easily identified by a pink cotton candy-like appearance at the tip of the ear. If you notice a significant amount of Gibberella in your fields, my recommendation is to harvest and sell this corn as soon as possible to prevent the mycotoxins from building up in the crop.
Figure 1: Gibberella Ear Rot
Fusarium ear rot (figure 2) is caused by the fungus Fusarium verticilliodes. This fungus can infect developing kernels and may not show signs of infection until later in the fall. Fusarium ear rot is exceptionally difficult to identify. The symptoms may not be visible, and the amount of mycotoxins in the ear may not correspond with the severity of symptoms. For scouting, the best way to identify Fusarium ear rot is to look for discoloration of isolated or patchy kernels on the ear, similar to the look of rotting teeth.If the crop is infected with Fusarium you need to harvest early and sell the grain right away.
Figure 2: Fusarium Ear Rot
Diplodia ear rot (figure 3) is caused by the fungus Stenocarpella maydis. This fungus will over-winter on corn residue and favors dry conditions prior to silking followed by wet conditions after silking. Just like the previous ear rots mentioned above, insect and bird damage will help promote this infection. Diplodia is easy to recognize, as there is typically a greyish white mold starting at the base of the ear. The presence of this disease does not indicate the presence of mycotoxins in the grain, but will reduce test weight and increase fine particles from kernel breakage.
Figure 3: Diplodia Ear Rot
Key Points
- Gibberella looks like pink cotton candy originating at the tip of the ear
- Fusarium presents as rotten kernels all throughout the ear (looks like rotting teeth)
- Diplodia is a greyish white mold originating at the base of the ear
- Early detection is key in harvesting high quality grain
- High risk fields should be harvested first and early
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