Released: February 03, 2003

Tree Lovers on Watch for Oak-Killing Disease

MANHATTAN, Kan. – What looks like a forestry horror story is showing up in photos taken from central California to southern Oregon. The pictures are making rhododendron lovers nervous, too.

The photos show whole forests dotted with the dead, wheat-colored tops of oak trees, including Shreve’s, coastal live, black, and tan oak trees. In some cases, that means every oak around.

The oaks are victims of a fungus-like organism called Phytophthora ramorun. But most people are calling the problem Sudden Oak Death, said Ned Tisserat, plant pathologist with Kansas State University Research and Extension. The disease also injures and can be carried by rhododendrons.

"The organism is a relative of the one that caused the Irish potato famine in the 1840s," Tisserat said. "That alone is enough to tell us Sudden Oak Death could have more dangerous potential than we’ve seen so far. Our best hope in the High Plains is that it is a water-loving organism. Otherwise, it could very well become a problem for some of our native oaks, including the pin oak."

The disease first showed up on the West Coast in 1995. The affected counties are now under quarantine and may not ship wood or wood products.

But Research and Extension scientists at the University of California-Davis are warning that the disease apparently can "ride" out of those areas on shoes and tires. It may even travel by wind.

So, state departments of agriculture – including those in relatively dry Oklahoma and Kansas – are on the lookout for signs the disease is spreading. They are surveying nursery stock coming in from other states for the presence of the Phytophthora organism.

"No one knows exactly what fosters the development of Sudden Oak Death, although the organism apparently requires relatively cool, moist conditions for infection. It may require rainy winters, as well as frequent rain during the early growing season," Tisserat said. "Since it seems to require high humidity, though, I don’t think Kansans need to worry. (Knock on wood!)"

Scientific lab analysis is the only way to identify whether a plant is carrying the disease, he said. So far, no red oak species have exhibited resistance.

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward, Communications Specialist
kward@oznet.ksu.edu
K-State Research& Extension News