Karnal Bunt |
|
|
|
Overview
Karnal
bunt is a fungal disease of wheat and triticale (a hybrid of wheat and
rye). The disease is caused by the fungus Tilletia indica Mitra,
also known as Neovossia indica. Typically, only a portion of
the wheat kernel is affected; this is why the disease is sometimes called
partial bunt. This disease is influenced by weather and climatic conditions
- the most severe infections occur when there is cool and wet weather
at the time the wheat is heading out. The disease was discovered in
1931 in the city of Karnal in northern India. The disease has been found
in Pakistan, Afghanistan, Iran, Mexico (since the early 1980's), Nepal,
Syria, and a few places in the United States.
The first discovery of Karnal bunt in the United States was in Arizona in March, 1996. Additionally, limited wheat growing areas of California, New Mexico, and Texas were regulated because of association with Karnal bunt infected seed or grain produced in the infested areas in Arizona. In 1997, Karnal bunt was also discovered in San Saba County, Texas. In succeeding years in the regulated areas, Karnal bunt infected grain was not detected or was at low levels. Karnal bunt was also not found in national surveys conducted annually in all wheat growing counties in the United States.
In the harvest season of 2001, wheat fields in additional Texas counties were found to be infected. Regulatory quarantines were further imposed to protect US wheat export markets. A team of USDA and state representitives are in North Texas to monitor the problem and regulate the movement of infected grain. The Department also established a task force to insure timely communication and information sharing relative to the program
Karnal bunt has minimal effect on quality and yield of wheat. The disease can be managed by use of clean seed treated and appropriate agricultural practices. Also, the disease cannot establish in new locations where climatic conditions are not favorable. For instance, infected seed has been planted all over India, however, it has not spread and remains localized. In addition, the processing of grain used for consumption often kills Tilletia indica, and grain used for consumption is not a risk for the spread of this disease.