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Corn Smut

Disease

Corn smut is a fungal disease that causes large, fleshy galls to grow on the ears and stalks of corn plants. While it can look alarming, it is a localized infection that primarily affects the yield and appearance of the affected ears.

Symptoms by part

Fruit

Large, white to gray, fleshy galls emerge from the kernels, eventually turning into dark, powdery black spores.

Stems

Swollen, tumor like growths appear on the stalk or at the nodes, which eventually burst to release masses of black fungal dust.

Causes

  • Warm, dry weather followed by periods of high humidity or rainfall.
  • Physical damage to the plant from insects, hail, or cultivation tools that creates entry points for fungal spores.
  • High nitrogen levels in the soil which can encourage rapid, succulent growth susceptible to infection.

Could be confused with

  • Common Rust · Rust appears as small, reddish brown pustules on the leaves rather than large, fleshy galls on the ears or stalks.
  • Bacterial Stalk Rot · This causes the stalk to collapse and emit a foul odor, whereas corn smut galls remain firm and fleshy until they mature.

Treatment

  1. Cut off and remove the galls from the stalks or ears as soon as you notice them, before they turn black and burst.
  2. Place all removed galls into a sealed bag and dispose of them in the trash rather than the compost pile.
  3. Clean any garden tools used to cut the galls with a diluted bleach solution to prevent spreading spores to other plants.

Without chemicals

  • Rotate your corn crops to a different part of the garden each year to reduce spore buildup in the soil.
  • Choose corn varieties that are labeled as resistant to smut.
  • Avoid wounding the plants during cultivation or weeding.

Preventing it

  • Remove and destroy all crop debris at the end of the season to prevent spores from overwintering in the soil.
  • Maintain balanced soil fertility to avoid excessive nitrogen, which promotes overly succulent tissue.
  • Control insect populations that cause physical damage to the corn ears and stalks.

Season

The warm growing season.

Spread risk

Moderate

Severity

Moderate

When to act

Act as soon as you see the white, fleshy galls forming to stop them from maturing into black spores. If the infection is widespread across your entire patch, remove and destroy the affected plants entirely.

Think it's Corn Smut?

This guide covers the general picture. Pocket Botanist looks at your actual plant from a photo and tells you what's really going on, how serious it is, and what to try first. Identification and a health check are free.

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Questions people ask

Is corn smut edible?
Yes, in some cultures, the young, immature galls are considered a delicacy known as huitlacoche and are harvested before they turn black and powdery.
Will corn smut kill my corn plants?
It rarely kills the entire plant, but it can significantly reduce the size and quality of the ears, leading to a poor harvest.
Can I compost the infected plant parts?
No, do not compost infected galls, as the spores can survive the composting process and reinfect your garden next year.

Plants it affects

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This guide was generated with AI and is general information, not horticultural advice. Read about how we build these guides.