Karnal Bunt

Last Modified: June 11, 2025
Bunted ear (Tilletia indica) of wheat.

Ruben Durán, Washington State University, Bugwood.org 

Karnal bunt, also called partial bunt, is a plant disease affecting wheat, durum wheat, and triticale (a hybrid of wheat and rye). The Karnal bunt fungus (Tilletia indica Mitra) and the plant disease it causes are harmless to people and animals and has little impact on crop yield or quality. Karnal bunt was first detected in 1996 in the United States in Arizona and then later in Texas and California.

APHIS regulates this disease because many trading partners require that U.S. wheat be certified as grown in areas free of Karnal bunt. Karnal bunt is quarantined to portions of two counties in Arizona, and the disease incidence in these regulated fields is minimal (usually less than 0.1 percent in the United States). APHIS also oversees an annual voluntary survey of grain delivered to elevators to check for Karnal bunt across the country.

Karnal bunt is usually identified after harvest, once the grains are separated and infected kernels are exposed. Here's what you'll see and smell:

  • Appearance
    • Bunted kernels are fragile, blackened, and sooty. The kernels' outer layer will have cracks, and if you press them, you'll see a black powder. In advanced infections, wheat kernels look like a boat or dugout canoe.
  • Fishy Odor

If the disease is severe, kernels will produce trimethylamine, which gives off a strong, fishy smell.

 

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Controlling Karnal Bunt

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Lynn Evans-Goldner

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