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KARNAL BUNT: What Is It?, Is It a Problem for Virginia Producers?, and Where Can You Find Up-To- Date Information?

Farm Management Update, June 1996

Eluned Jones and Carrie Kennedy

The following information is excerpted from articles on the WWW, and from information reported in the National Grain and Feed Association Newsletter. Although Karnal bunt does not represent a problem to the Virginia wheat industry, a basic understanding of the issues involved will help producers to follow announcements in the agricultural press, and understand the reasons for significant resource allocation to the problem by federal agencies.


Karnal bunt is a smut fungus (Tilletia indica Mitra) of wheat, durum wheat, and triticale. The common name 'Karnal' derives from the location of first reporting near the city of Karnal in India in the 1930's. Although Karnal Bunt has been present in northwestern Mexico since 1982 it was not known to exist in the U.S. until March of this year. USDA-ARS confirmed the presence of Karnal bunt in certified durum wheat from Arizona during routine testing of seed samples by the Arizona Department of Agriculture. Because many countries to which the US exports wheat have a moratorium on wheat infected with Karnal bunt an immediate quarantine was placed on all classes of wheat exports for several weeks from the US until non-durum classes of wheat were certified as free on the disease.

Disease impacts are 2-fold: (1) Reduced grain production, and (2) Decreased grain quality. Flour milled from infected kernels is discolored with an unpleasant, fishy odor and off-flavor. The disease is non-toxic, unlike the Aspergillus fungi that produce toxins, but 3% or more of bunted kernels is considered unsatisfactory for human consumption.

How Does it Spread?

Karnal bunt is spread by spores. Infection occurs during the flowering stage of the plant. Ideal conditions for infection are cool weather and rainfall or high humidity. Most importantly for quarantine measures, the spores can survive for 5 years.

Spores can be windborne but are relatively fragile. Spread is most likely via plant parts, seeds, soil, elevators, buildings, farm equipment, tools and vehicles - hence the reason for the interstate quarantine imposed immediately in the area where infected samples were located.

There are currently no good measures of control once the plant is infected. Partial control can be achieved by seed treatment and foliar fungicides but the best method is to plant non-host crops on contaminated fields for 5 years.

Extent of Infection in U.S.

In late March and early April Federal quarantine was placed on the entire State of Arizona; Imperial county and eastern Riverside county, California; Dona Ana, Hidalgo, Luna, and Sierra counties in New Mexico; and El Paso and Hudspeth counties in Texas. This accounts for around 300,000 acres of approximately 74 million acres of wheat indicated by the US planting intentions report. However, this accounts for about 20% of the wheat planted in the quarantine area.

In the quarantined areas every field of wheat, durum and triticale is being tested for the presence of Karnal bunt.


The disease cannot be visibly detected in plants in the field. Infected grain does not display symptoms until it reaches maturity. Grain must be removed from the head and examined for the black powdery spore mass within the endosperm at the embryo end of the kernel, and a fishy odor.

Any suspected kernels should be sealed in a plastic bag or container and sent to APHIS (Animal and Plant Health Inspection Service.), Plant Protection and Quarantine Service. For specific information on identification and assistance producers should contact APHIS or a Plant Pathologist for assistance.


In the affected areas the interim quarantine covers not only the wheat but also any medium by which the spores can be carried into non- infected regions. [For producers familiar with the restrictions for interstate movement of cotton production equipment under the boll weevil eradication program, the restrictions are very similar.]

Samples of wheat from quarantined ares that test negative may move to a milling facility for flour or feed, or into export as long as shipment is consistent with the country of destination requirements.

Wheat that tests positive for Karnal bunt cannot be moved outside the quarantined area. Wheat can be milled within the quarantine area for flour, from there the flour can move without restriction but the mill by- products must be heat treated. Wheat can also be used in feed if it is heat treated, or the supplies testing positive can be destroyed. Protocols are being finalized for handling infected wheat.

Economic impacts

Producer impacts:

  1. Cost of managing sampling and testing.
  2. Cost of decontaminating machinery between fields during harvesting.
  3. Possible loss of revenues from contaminated fields for 5 years through having to plant non-host crops.
  4. Where seed known to be infected has been planted (Texas and New Mexico) producers can plow down the crop before maturity and limit further infection. Producers will be eligible for a $300 per acre payment, but may not be eligible for crop insurance indemnity.

Elevators and Millers impacts:

  1. Loss in compensation - USDA will pay a one-time charge of 50% of the costs of cleaning and disinfecting grain handling facility that is contaminated, up to $20,000 maximum.
  2. USDA will pay compensation to grain handling facilities for full loss in market value of commodities found to be contaminated.

Industry impacts:

  1. Possible loss of exports due to quarantine measures.
  2. Possible costs in assuring customer perceptions of quality.

Access to Information Through Internet

Updated information regarding the Karnal bunt outbreak is available on the Karnal bunt homepage maintained by the Animal and Plant Health Inspection Service (APHIS). Any individual with a connection to the internet can access this homepage at The homepage gives a summary of the current situation in the US and quick links to other information, broken down by topic. These links include: basic information about Karnal bunt eradication; Karnal bunt national survey; Karnal bunt situation report update; Karnal bunt Federal quarantine; Karnal bunt press releases; Karnal bunt fact sheet; and phytosanitary information, including the trade requirements of other nations. Questions or comments regarding the Karnal bunt program can be e- mailed to APHIS at

The following table includes a number of USDA agency sites that provide publications, press releases, and a variety of current information.

US Department of Agriculture (USDA)
Allows easy access to USDA public information. Check out How to Get Information.
Agricultural Marketing Service (AMS)
Provides Agricultural Statistic updates, & 1996 Farm Bill Updates.
Economic Research Service (ERS)
Provides economic reports, such as Situation and Outlook, and Agricultural Outlook.
National Agricultural Statistics Service (NASS)
Provides statistical information via the USDA Economic & Statistical System.
Grain Inspection, Packers & Stockyards Administration (GIPSA)
Includes publications & current news from Federal Grain Inspection Services (FGIS) and the Packers & Stockyards Program.
Foreign Agricultural Service (FAS)
Provides current trade data, information on US export assistance and export programs.
Animal & Plant Health Inspection Service (APHIS)
Provides lists of APHIS regulations and an Import-Export Directory. Plus, a link to Plant Protection and Quarantine (PPQ).

This is just a sample of the agencies that can be accessed via the information superhighway. USDA has over 75 related sites. The Federal Web Locator, maintained by the Villanova Center for Information Law and Policy, will allow you to search these sites using keywords or organizational names.

After accessing the Federal Web Locator at Fed-Agency/fedwebloc.html, scroll down to Search the Federal Web Locator. Type in a keyword expression and then select submit search. For example, if you were to do a search using APHIS, the Federal Locator would respond with a link to the Animal & Plant Health Inspection Service s web site. The locator also provides links to each federal agency website. To use this feature, scroll down to Federal Quick Jumps and select USDA from the choices under Federal Executive Agencies: Departments.

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