Tree Heartwood Extracts Thwart Sudden Oak Death
Microbe By Laura
McGinnis April 8, 2008
Help may be on the way for more than 100 plant species susceptible to
sudden oak death (SOD). Agricultural Research Service (ARS) plant physiologist
Manter has found that extracts from tree heartwood can limit the growth of
Phytophthora ramorum, the microbial agent that causes this devastating
Since it surfaced on the West Coast in the mid-1990s, SOD has killed
an estimated 1 million oaks and tanoaks. For years, scientists have known that
tree heartwood contains protective antimicrobial compounds, but it wasn't known
whether these compounds could offer protection against P. ramorum.
Manter, with the
Soil Plant Nutrient Research Unit, Fort Collins, Colo., and his colleagues
exposed P. ramorum spores to compounds, wood chips and essential oils
extracted from heartwood. They found that extracts from incense cedar, western
redcedar, Alaskan yellow cedar, western juniper and Port Orford cedar destroyed
P. ramorum spores and inhibited fungal cell growth.
The western redcedar and incense cedar extracts damaged twice as many
spores as the extracts taken from Alaskan yellow cedar, western juniper and
Port Orford cedar. Douglas fir and redwood extracts, which were also examined
in the study, showed little to no antimicrobial activity against the pathogen.
Tree heartwood extracts could provide easy-to-use, environmentally
friendly, effective tools for SOD control. Heartwood could be processed into
shavings, sawdust, wood chips or liquid extracts. These materials could then be
distributed in areas with high human activitiessuch as park trails,
walkways, and bike pathsto reduce spore movement and prevent the spread
of the disease.
more about this research in the April 2008 issue of Agricultural
ARS is the chief scientific research agency of the U.S. Department of
Agriculture (USDA). This research was
conducted with scientists from USDA's Forest
Service, and Oregon State University.