Common Corn Stalk Rot Diseases: Identification and Comparison

In 2024 alone, over 165 million bushels were impacted by corn stalk rot diseases in the U.S.1 Stalk rots in corn can be tricky to manage and prevent, but the first step comes down to proper identification.

Several types of corn stalk rots could impact your corn, and knowing how to tell the difference between these diseases can help you make the right management decisions for your fields. All stalk rots diminish a corn plant’s ability to transport water and take up nutrients. This ultimately weakens the stalk and can make it more vulnerable to lodging in high winds.

This article will help you identify and compare the symptoms of different corn stalk rots so you can tell what’s going on with your crop.

Anthracnose stalk rot in corn

Anthracnose stalk rot, one of the most common stalk rots in corn, is caused by the fungal pathogen Colletotrichum graminicola. It’s most prevalent in warm, humid regions and can show up in any stage of growth, but it usually occurs in warm, cloudy weather after silking. It’s more common in fields with high residue and continuous corn. Anthracnose stalk rot in corn infects plants through wounds left by insect damage (especially European corn borer) or some other type of injury, like hail or mechanical damage.2

Anthracnose stalk rot symptoms

• Shiny black discoloration on the outer stalk near the nodes
• Shredded-looking pith inside the stalk
• Tan to reddish lesions on the rind
• Hollow and easily-lodged stalks (in advanced stages)
• Top dieback or browning of the upper parts of the plant
• No tiny fruiting structures (pycnidia) appear on the exterior of the stalk, as they do with Gibberella and Diplodia stalk rots

Gibberella crown rot and stalk rot in corn

Gibberella crown rot and stalk rot are also caused by the fungus Gibberella zeae, the same pathogen that causes head scab in wheat and Gibberella ear rot in corn. That’s why this disease is more prevalent in wheat-corn rotations and continuous corn. It prefers warm and wet conditions and will occur shortly after pollination. Infections can travel through roots, via injuries on the stalk, or on leaf scars.3

Gibberella crown rot and stalk rot symptoms

• Pith will appear stringy and have a slight pink tint
• Stalk exterior will have tiny black or blue round fungal structures that can be scraped away with a fingernail
• Leaves can suddenly turn a dull green or gray

Fusarium stalk rot in corn

There are several species of Fusarium spp. that can cause Fusarium stalk rot in corn. The fungal mycelium, or the root-like part of a fungus, will overwinter in corn residue and can quickly spread via the wind and splashing in hot, dry years.4

Most of the symptoms will start to be noticeable near R5 and can even be found in healthy stalks. However, Fusarium stalk rot will occur only when conditions are warm and dry, and plants are stressed.5

Fusarium stalk rot symptoms

• The lower stalk will yellow, and the leaves will be dull green
• Stalk pith is deteriorated, appears hollow and shredded, and will have a pink or salmon color
• Plants may die before maturity, and roots are often rotted
• No tiny fruiting structures (pycnidia) appear on the exterior of the stalk, as they do with Gibberella and Diplodia stalk rots

Diplodia stalk rot in corn

Diplodia stalk rot is very similar to the other stalk rots already mentioned. Stenocarpella maydis causes both Diplodia stalk rot and Diplodia ear rot. If the weather has been dry before silking and then warm and wet after silking, there’s a good chance Diplodia stalk rot will develop.6 Since this fungus will overwinter in corn residue, fields with continuous corn are most susceptible to infection.7

Symptoms

• Symptoms can look like frost damage (wilted and grayish-green coloration)
• Pith inside the stalk becomes destroyed, but lacks the pink color often found with Fusarium and Gibberella stalk rots
• Small black dots on the exterior of the stalk will develop and be embedded into the surface of the stalk, but they can’t be scraped off, unlike the fungal dots associated with Gibberella stalk rot
• Stalk can feel rough like sandpaper
• White mold can develop when fields are very wet

Many of these fungal stalk rots have similar symptoms, and to properly identify corn stalk rots, look for those unique symptoms that give you a clue as to what you are dealing with. That way, you can take the necessary steps to deal with these diseases early.

Experts are available to help you make your diagnosis and decisions. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative.

________________________________________________

Endnotes

1. Sikora, Ed, et al. “Corn Disease Loss Estimates from the United States and Ontario, Canada – 2024.” Crop Protection Network, 2024, https://cropprotectionnetwork.org/publications/corn-disease-loss-estimates-from-the-united-states-and-ontario-canada-2024.
2. Esker, Paul D., Adriana Murillo-Williams, and Alyssa Collins. “Anthracnose Stalk Rot.” Cornell CALS Field Crops, Cornell University, https://cals.cornell.edu/field-crops/corn/diseases-corn/anthracnose-stalk-rot.
3. “Gibberella Crown Rot and Stalk Rot of Corn.” Crop Protection Network, 19 Mar. 2019, https://cropprotectionnetwork.org/encyclopedia/gibberella-crown-rot-and-stalk-rot-of-corn.
4. “Fusarium Stalk Rot of Corn.” Crop Protection Network, 19 Mar. 2019, https://cropprotectionnetwork.org/encyclopedia/fusarium-stalk-rot-of-corn.
5. Freije, Anna, Kiersten Wise, and Bob Nielsen. “Diseases of Corn Stalk Rot.” Purdue Extension, BP-89-W, Purdue University, 2020, https://www.extension.purdue.edu/extmedia/BP/BP-89-W.pdf.
6. Freije, Wise, and Nielsen. “Diseases of Corn Stalk Rot.”
7. “Diplodia Stalk Rot of Corn.” Crop Protection Network, 19 Mar. 2019, https://cropprotectionnetwork.org/encyclopedia/diplodia-stalk-rot-of-corn.