University of Illinois

No. 17/July 18, 1997

Karnal Bunt Update

Karnal bunt of wheat (KB), caused by the fungus Tilletia indica, is still a concern in the United States, primarily to the wheat exporters and not to the producers. The disease causes little yield loss but does impart a fishy smell to wheat products, even at kernel infection levels as low as 3 percent. KB was initially found in March of 1996 in Arizona and subsequently in New Mexico, California, and Texas. At present, it has not been found in midwestern states.

Currently, USDA is continuing to sample fields in most wheatproducing states. The sampling scheme for this year is a bit different because a predefined number of samples are to be collected from each county, depending on the estimated size of the wheat crop. County Extension workers are again assisting in this effort, and samples have already been received and are being processed. In Illinois, we will process about 400 samples this year. Each sample will be checked microscopically for spores and additional tests performed if a positive is found. However, this is very unlikely, based upon our experiences.

In addition to this survey, the USDA is actively involved in determining if a ryegrass bunt, which is very similar in size and biological characteristics to Karnal bunt, can cause KB. Some samples from Tennessee and other southern states were initially judged positive for KB but were later determined to be infested with ryegrass bunt. Currently, however, there is concern that this bunt can cause disease in wheat. On June 17 of this year, the Arizona Department of Agriculture issued a press release stating that spores of the ryegrass bunt found in a ryegrass­wheat mixture did cause Karnal bunt disease in wheat. The Animal, Plant Health Inspection Service (APHIS) of USDA, the agency charged with regulation of KB has since issued a statement that they do not anticipate a change in their policies concerning this bunt until further research can be undertaken.

In early July, USDA proposed to amend the KB regulations by adding compensation provisions for certain growers, millers, and others who incur losses and expenses due to KB in the 1996­1997 crop season. Compensation would be based upon a confirmed detection of KB by APHIS and would vary depending upon the situation. Growers eligible for assistance are those in designated areas of the Southwest, as well as wheat handlers in these areas.

USDA is also actively working to maintain wheat export markets to countries with concerns about KB. As of May 7, many countries have agreed to accept US wheat products with no changes to phytosanitary requirements or to accept wheat products with a standard APHIS additional declaration. Other countries are currently negotiating with USDA to clarify the language of agreements.

For more information, there is an APHIS web page
or the KB page
H. Walker Kirby, Extension Plant Pathology, (217)333-8414