Choke disease, caused by the fungus Epicloë typhina, is another invader from Europe. Grayish-white to orange in color, the growths, or stroma, were first discovered in the United States in 1996 on an infected tiller in Oregon. The following year, it was found in four fields, all of the same experimental variety. By 1998 the fungus was found throughout the Northwest.

My research indicates that choke disease has not been found elsewhere in the U.S. In fact, I’d never heard of it prior to attending research presentations in Binghamton last March. So, should we be concerned about choke disease in orchardgrass? Yes!

Oregon’s Willamette Valley is almost the exclusive orchardgrass seed-producing area of the country, accounting for 95% of the seed produced. All of our local seed supplies for orchardgrass come from this region. Orchardgrass is the primary grass I recommend for seeding all types of pastures due to standards set by Natural Resources Conservation Service (NRCS). Currently, orchardgrass seed supply is down, so prices are up. Yield loss estimates were 9% for 2004 which equates to an estimated $820,000 farm-gate loss.

Choke disease doesn’t show symptoms until prior to flowering. When infected, the flower head cannot emerge from the sheath. Disease levels are low – less than 2% -- the first year of production and increase as the stand becomes older.

The fungus spreads apparently by spores, although researchers are unsure of the process. Disease levels increase year-to-year (polyetic) in established fields, with no increase within a year (monocyclic). That is why it’s essential for seed growers to annually inspect fields for incidence.

There are no treatment or management tools, other than plow down, for choke disease. And there are currently no varieties resistant to the disease.

Since choke is a disease that infects flowering heads, it’s not a problem in hay or pasture production. It’s not a seed-borne pathogen. Surveys searching for diseased fields have been conducted in Oregon annually. Research is underway to determine how the disease is transmitted, along with cultural and climatic requirements. We need to understand these factors before progress can be made with management options, whether through breeding for disease resistance or treatment approaches.

Nancy Glazier is the Small Farms Support Specialist with the Northwest New York Dairy, Livestock and Field Crops Team. Reach her in Yates County at 315-536-5123. Email: nig3@cornell.edu
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