UMass Extension Vegetable Program

Corn Smut

Ustilago
maydis

Common smut is found wherever sweet corn is grown; its incidence and severity are determined by cultivar resistance, weather conditions, and the amount of inoculum available to start an epidemic. It is generally of minor economic importance, but can become locally important.

Identification: 

The pathogen affects only sweet and field corn and its symptoms are easily recognized. The disease results in the appearance of smooth, shiny galls or boils, which range from1 inch to 4 inches in diameter and can occur on all aerial parts of the plant. They are most common on developing ears, where the developing kernels are transformed into boils filled with masses of black, powdery spores which are easily dispersed by wind. In the southern hemisphere, corn smut is considered an edible delicacy known as cuitlacoche and the value of the diseased crop exceeds that of the healthy one.

Life Cycle: 

Common smut overwinters in soil, infected crop debris, and may contaminate seed. Wind, hail, and insects can produce wounds that provide a point of injury.

Cultural Controls & Prevention: 
  • Crop rotation.
  • Avoid prolonged leaf wetness.
  • Removal and destruction of small galls before the spores are released may be useful in small areas.
  • Avoid excessive nitrogen levels.
  • Avoid mechanical injury of plants when working plants.
  • Resistant cultivars.
  • Fungicides will not provide effective control of common smut.
Chemical Controls & Pesticides: 

 For Current information on disease recommendations ins specific crops including information on chemical control & pesticide management, please visit the New England Vegetable Management Guide website.

Crops that are affected by this disease: