Tree heartwood extract limits growth of Phytophthora ramorum

USDA and university researchers found extracts from tree heartwood can limit the growth and sporulation of Phytophthora ramorum, the fungus that causes sudden oak death. The extracts can’t cure infected trees, but they could be used to halt the disease’s spread.

Daniel Manter, a plant physiologist at the USDA-ARS Soil Plant Nutrient Research Unit at Fort Collins, Colo., is working with Rick Kelsey of the USDA Forest Service and Joe Karchesy at Oregon State University. The team exposed P. ramorum spores to various compounds, wood chips and essential oils extracted from heartwood. Extracts from incense cedar, western red cedar, Alaska yellow cedar, western juniper and Port Orford cedar destroyed the P. ramorum spores and inhibited the growth of fungal cells.

“Under a microscope you can actually see the spores explode,” said Manter. “The outer membrane ruptures and releases the cell contents after it’s been exposed to the extracts.”

Extracts from western red cedar and incense cedar damaged twice as many spores as the other species.

Currently there are no effective commercial fungicides in use in the United States to counter the spread of sudden oak death. Using tree heartwood extracts has the potential to be an easy-to-implement, environmentally friendly, and effective method of SOD control, Manter said.

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For more: Daniel Manter, ARS Soil Plant Nutrient Research Unit, (970) 492-7255; daniel.manter@ars.usda.gov.

June 2008