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Karnal Bunt

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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.

What To Look For

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.

Tap any image to view larger size.


Show Info

Two heads of common wheat with symptoms of Karnal bunt. Ruben Durán,

Washington State University, Bugwood.org

Wheat kernels and bunted wheat kernels caused by Tilletia indica. Department of

Plant Pathology, North Carolina State University, Bugwood.org
How To Prevent This Disease

You can reduce the risk of spreading Karnal bunt by using clean seed, ongoing

sanitation, sound agricultural practices, and following quarantine regulations for

both imported regulated articles and impacted domestic areas. 

How It Is Treated
You can manage the disease by cooperating with State and Federal officials and

following regulations. It is equally important to use clean seed, proper sanitation,

and sound agricultural practices.

Report Plant Pests and Diseases

Have you seen this pest or signs of pest damage? Immediately report your findings.

Find your State plant regulatory official

Find your State plant health director

Controlling Karnal Blunt

Current Status

A successful quarantine and national survey program have confined Karnal bunt to

portions of one State: Arizona. Because the fungus-causing disease poses no harm

to people or animal health, there are no Federal food regulations concerning Karnal

bunt. Every year since 1996, APHIS has coordinated a Karnal bunt national survey in

wheat-producing counties, outside of regulated areas in Arizona. To date, Karnal

bunt hasn't been found in these surveys.

February 2024 Regulated Area Map (823.91 KB)

April 2023 Regulated Area Map

January 2023 Regulated Area Map

Regulated Areas

Regulated Articles

APHIS' Response

Survey Plan

National Karnal Bunt Survey Plan

Survey Maps

2022 (1.95 MB)

2021
2020

Domestic Regulatory Information

Code of Federal Regulations

Domestic Regulations - 7 CFR 301.89-1 through 301.89-16

Federal Register Notices

Federal Orders

February 14, 2024, APHIS Reduces Karnal Bunt (Tilletia indica) Regulated Areas

in Maricopa and Pinal Counties in Arizona (159.17 KB)

April 24, 2023,  APHIS Amends Karnal Bunt (Tilletia indica) Regulated Areas in

Maricopa County in Arizona

December 29, 2022, APHIS Amends Karnal Bunt (Tilletia indica) Regulated

Areas in La Paz, Maricopa, and Pinal Counties in Arizona

August 17, 2022, APHIS Amends Karnal Bunt (Tilletia indica) Regulated Areas in

La Paz, Maricopa, and Pinal Counties in Arizona

Import Regulatory Information

APHIS may recognize an area as free of Karnal bunt whenever we determine that the

area meets the requirements of the International Standard for Phytosanitary

Measures (ISPM) No. 4. To provide the public with current, valid information, we will

publish a notice in the Federal Register and maintain on our Karnal bunt web pages

a list of the specific areas where Karnal bunt is not known to occur. Areas listed as

being free from Karnal bunt are subject to audit by APHIS to verify that they

continue to merit such listing.

Import Regulations - 7 CFR 319.59

Areas Outside the United States Where Karnal Bunt Is Known To Occur

Karnal bunt is known to occur in the following areas outside the United States:

Country Areas Within a Country

Afghanistan
Country Areas Within a Country

India

Iran

Iraq

Mexico Chihuahua, Guanajuato, Jalisco, Michoacan, Queretaro, and Mexicali

Valley in Sonora and Baja California

Nepal

Pakistan

South

Africa

Karnal Bunt Pest-Free Areas

The APHIS Administrator may recognize an area as free of Karnal bunt whenever

they determine that the area meets the requirements of the International Standard

for Phytosanitary Measures (ISPM) No. 4, “Requirements for the establishment of

pest free areas.” The international standard was established by the International

Plant Protection Convention of the United Nations' Food and Agriculture Organization

and is incorporated by reference in 7 CFR § 300.5. To provide the public with current,

valid information, APHIS will publish a notice in the Federal Register and maintain on

our website a list of the specific areas that are approved as areas in which Karnal

bunt is not known to occur. Areas listed as being free from Karnal bunt are subject to

audit by APHIS to verify that they continue to merit such listing.

The following area of the Mexicali Valley in Mexico has been determined to be free

from Karnal bunt:

Those portions of the municipality of Mexicali, in the State of Baja California,

and the municipality of San Luis Rio Colorado, in the State of Sonora, that are

included in the Distrito de Desarrollo Rural (Rural Development District) 002 Rio

Colorado

Except for wheat (Triticum spp.) plants, which are prohibited importation under §

319.37, § 319.59, or both, approved articles that are from recognized pest-free areas

may be imported into the United States subject to all of the following conditions:

1. The articles are offered for entry at the port of Calexico, CA.
2. The articles offered for entry are made available for examination by an

inspector and remain at the port until released, or authorized further movement

pending release, by an inspector.

3. The articles are accompanied by a phytosanitary certificate issued by the

Mexican national plant protection organization that certifies the articles are

from the area of the Mexicali Valley described above and remained within that

area before and during their movement to the United States.

Information for Cooperators

Program Manual

Appendix D - Laboratory Procedures

Reports and Assessments

USDA Economic Research Service (ERS) Outlook Report: Economic Implications

of Ending the Issuance of Karnal Bunt Phytosanitary Wheat Export Certificates -

This report provides the results of ERS research on the economic consequences

of ending the USDA Karnal bunt certification program for U.S. exports to

countries that ban import of wheat from countries known to have the disease.

Contact Us

Lynn Evans-Goldner

National Policy Manager

Email: lynn.evans-goldner@usda.gov

Phone: 301-851-2286