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Since
2003, the WSU Puyallup Ornamental Plant Pathology Program has been
conducting research on Phytophthora ramorum relating to host
range, epidemiology, and evaluating potential control options.
In
response to industry concerns, WSU recently built a new, quarter-million-dollar
biocontainment facility at Puyallup. This facility will greatly
increase the capacity of WSU to address critical research questions
relating to the establishment, host susceptibility, spread and management
of P. ramorum. A new molecular lab is also being developed
to enhance research relating to the detection, spread, and genetics
of this pathogen.
Additionally,
WSU initiated a research project last spring to examine factors
influencing P. ramorum infection in Christmas tree plantations
with funding provided by a two-year USDA Forest Service grant. Work
on this project is occurring at the Black Road Christmas Tree Farm
near Los Gatos, CA. This is a 23-acre U-cut Christmas tree farm
that was established in 1966. Conifers being grown at this site
include Douglas-fir, grand fir, giant sequoia, scotch pine, white
fir, and California red fir. Some known P. ramorum hosts
in the forest adjacent to the edge of the farm include: California
bay laurel, madrone, big leaf maple, false solomon seal, toyon,
coast redwood, and tanoak. Dieback on some of the grand and Douglas-fir
along the interface between the infected forest and the Christmas
tree farm appears to have occurred at least 4 years ago. During
2005, conditions were very favorable for disease development. Preliminary
results from this study indicate that most of the infected Christmas
trees occurred within 2 meters of the edge of the P. ramorum-infected
bay laurel forest canopy. Virtually no infection was evident on
Christmas trees that were >5 meters away from the forest edge.
The
Forest Service, Washington State Pesticide Commission, Pacific Northwest
Christmas Tree Association, IR-4 program, and the WSDA Nursery Research
Program are also supporting research at WSU Puyallup to determine
the effectiveness of various fungicides in protecting conifers and
rhododendrons from infection by this pathogen. This work has shown
that several traditional contact materials, such as mancozeb, and
the systemic material Subdue MAXX, have the potential to provide
excellent control of diseases caused by P. ramorum. However,
growers and regulatory agencies are concerned that the use of fungicides
may be masking symptom development, thus making it harder to prevent
the spread of this pathogen on infected nursery stock. Now that
the new biocontainment facility is completed at WSU Puyallup, additional
studies will be conducted to determine the residual effectiveness
of fungicides and determine if any of them have the potential to
mask symptom development on infected plants.
For
more information on sudden oak death research at WSU please contact
Gary Chastagner.
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