Preventing Karnal Bunt: Precautions, Awareness Key

By Michael Schommer,
Communications Director,
Minnesota Department of Agriculture

Karnal bunt has not been found in Minnesota, and the state’s wheat industry along with the Minnesota Department of Agriculture would like to keep it that way.

A fungus that can infect the wheat kernel and ruin a portion of the wheat head, Karnal bunt, was first discovered in India in 1931.  In following years, it turned up in four other central Asian countries.  Karnal bunt reached Mexico in the late 1960s – most likely through contaminated seed – and can be found in the northwestern corner of the country.

Karnal bunt is one of six types of fungi that cause a family of diseases known as smuts.  However, unlike most smuts, Karnal bunt does not pose a significant risk of yield loss.  Instead, it turns portions of some of the kernels on the wheat head into spores. For this reason it is sometimes called partial bunt.  These “bunted” wheat heads have a dark brown color and an unpleasant, fishy odor.  While bunted wheat is not a health risk to humans, any wheat containing more than 3% bunted kernels is considered unfit for human consumption.

Bunt is most often spread through the movement of infected seed and other wheat products, but it can also be spread by contaminated harvesting or grain handling equipment.  Over the years, many countries developed import restrictions to prevent the introduction of Karnal bunt. The United States and more than 20 other countries prohibit the importation of wheat seed, plants, unprocessed straw, chaff and mill products (other than flour) from countries where Karnal bunt is known to occur.

Despite these precautions, Karnal bunt found its way into the U.S. in 1996.  It first popped up in Texas, but in the last two years it has spread to New Mexico, Arizona and California.  Those states now face heightened regulations and prohibitions to prevent the disease from spreading. 

Combines and other equipment used in a county with Karnal bunt must be steam-cleaned to get rid of any spores that it might have picked up. Also, before any wheat is allowed to move out of infected counties, it must be certified free of bunt spores. This certification process takes up to two months, a delay that can make shipping the wheat to domestic or foreign markets very difficult.  As a result, wheat grown in bunt-infested counties loses much of its value and usually ends up being used as livestock feed.

The speed with which Karnal bunt spread from Texas has officials concerned that it may soon find its way to other wheat-growing regions such as Minn-esota’s Red River Valley.  To avoid that and to reassure concerned wheat buyers in other countries, agriculture officials have established a certification program for Minnesota and other non-infested wheat growing states.

Under this program, the Minnesota Department of Agriculture takes random wheat samples from grain elevators around the state. The samples are sent to a U.S. Department of Agriculture testing facility, where each sample is examined for the presence of bunt spores.  If any spores are found, the next step is to determine if any of the wheat kernels are bunted. If bunted kernels are found, the wheat cannot be certified as bunt-free.

Bunted wheat loses much of its market value because it can no longer be shipped outside the immediate area.  To help lessen the disease’s economic sting, the U.S. Department of Agriculture offers a compensation program to farmers or elevators who report suspected bunt cases. 

Geir Friisoe is the section manager responsible for supervising the MDA’s wheat sampling program.  He says that while Karnal bunt is a threat to Minnesota wheat, the risk isn’t as high as it is in other states.

“States that grow a lot of winter wheat are at a much greater risk for Karnal bunt than states where spring wheat dominates,” Friisoe says.  “For some reason, spring wheat seems to be less susceptible to this disease. That’s good news for Minnesota, since we grow spring wheat almost exclusively.”

Friisoe says Minnesota wheat farmers can lower their risk even more by taking a few precautions.

“I would urge Minnesota farmers to purchase seed that has been certified by a crop improvement association or by our MDA seed lab as being free of Karnal bunt,” Friisoe says.  “If you’re hiring custom combiners, I would be sure to ask them where they’ve been previously.  If they’ve been working in Texas, Arizona, New Mexico or California, look at their machinery to see if it’s clean.  If not, insist that they have it steam-cleaned before entering your fields.  Finally, producers, harvesters and handlers should look for bunted kernels that are fragile, dark in color, and fishy smelling. If bunt is suspected, call MDA right away and we will conduct tests to determine if it is Karnal bunt or some other wheat disease.”

Several states have recently begun a push to have Karnal bunt certification requirements eased.  While this may be in the interest of states with the bunt or neighboring states, such a move could have serious repercussions for Minnesota and other states certified as being free of Karnal bunt. If states were to stop certifying, it would hurt Minnesota’s ability to export its wheat.  Without assurance that U.S. wheat shipments are bunt-free, foreign buyers might look elsewhere when purchasing.

Friisoe says discussions are underway at the national level to address this issue. Ultimately, he says, certification should not be eliminated unless it can be done in a way that doesn’t hurt farmers’ ability to export their wheat. “USDA is developing an overall strategic plan on this, and I hope they will find a reasonable solution to this,” he says.  “We shouldn’t solve a problem for one group of farmers by creating a problem for others.”

The Minnesota Department of Agriculture has prepared a brochure on Karnal bunt, which can be found on the web sites of the MDA www.mda.state.mn.us and the Minnesota Wheat Research and Promotion Council www.smallgrains.org. To request the brochure by mail, call the MDA at 1-800-967-2474 or the MWRPC at 1-800-242-6118.