Karnal bunt, caused by the fungus Tilletia indica Mitra, is a disease of wheat and triticale (a hybrid of wheat and rye). The fungus and the plant disease that it causes are harmless to humans and animals. KB was first reported in 1931, infecting wheat growing near the city of Karnal in the Indian state of Haryana - hence the name “Karnal” bunt. Since its discovery in India, KB has been found to occur in Afghanistan, Iraq, Iran, Nepal, Pakistan, South Africa, Mexico, and the United States. Karnal bunt is thought to have been inadvertently introduced into the United States (U.S.), decades ago, on infested seed. Through a successful quarantine and national survey program, this disease is currently confined to one U.S. State - Arizona. Karnal bunt has significance as an export challenge because it is considered by some U.S. trading partners to be a quarantine pest, while the U.S. considers it to be a quality pest that seldom results in significant yield losses. Many U.S. trading partners will not accept U.S.-origin wheat unless the wheat is certified to be from areas of the U.S. where Karnal bunt is not known to occur. Every year since 1996, USDA APHIS has coordinated a cooperative Karnal bunt national survey in wheat-producing counties outside of known regulated areas in Arizona. To date, Karnal bunt has not been found in U.S. national surveys.
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