Corn Smut Disease

Corn Smut

Proven, natural and organic strategies for identifying and treating corn smut in home gardens.

Frequently found in backyard gardens and small farms, corn smut is caused by the fungus Ustilago zeae and can appear in the stalks, leaves, tassels or ears. Symptoms are most commonly noticed when the ears produce mushroom-like tumors or galls. These “swellings” begin as small, whitish-gray irregularities which expand and turn black as they fill with spores. Ear galls can grow to 4- to 5-inches in diameter and release thousands of spores as they rupture. These fungal spores are blown by the wind for considerable distances to infect new plants. Galls on leaves remain small and eventually become hard and dry.

Corn smut overwinters on garden debris and in the soil. It is carried by wind, rain and irrigation and does best in hot, dry weather. Spores may remain viable for 5- to 7-years. Wounds from various injuries, including cultivation and abrasion from blowing soil, provide points for the fungus to enter the plant.

Treatment

  • Choose the best resistant varieties, such as silver king, fantasia, brilliant and seneca sensation, when available.
  • In backyard gardens, collecting and destroying galls before the dark fungal spores are released is suggested. This will limit the number of available fungal spores and help break the disease-cycle.
  • Reduce infection points by avoiding injury of roots, stalks and leaves during cultivation.
  • Prevent damage from insects, such as corn borers, with Monterey® Garden Insect Spray or other organic insecticide.
  • Fungicides are NOT an effective control option since the disease is so widespread and can persist in the soil for years.
  • High nitrogen fertilizers may increase the severity of the disease — use a balanced organic fertilizer in the vegetable garden.
  • Remove and destroy all garden debris after harvest and practice crop rotation the following year.
  • Bag or burn infected plant parts — do NOT compost.

Note: Corn smut can pass through the digestive tracts of animals and is often spread while using manures.

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