Second Science Symposium
January 18 - 21, 2005
Effect of Sanitary Measures on the Survival of P. ramorum in Soil.
M.M. Aveskamp, Plant Protection Service, P.O. Box 9102,
6700 HC Wageningen, The Netherlands; email@example.com;
P.J.M. van Baal and J. de Gruyter, Plant Protection Service, P.O. Box
9102, 6700 HC Wageningen, The Netherlands
In May 2003, a Phytophthora ramorum infested garden in the surroundings of Nijmegen, the Netherlands, was cleared of infected Rhododendron shrubs by cutting the plants back at 30 cm. In an experiment the remaining parts of the approximately 70 years old Rhododendron plants were treated with (1) thiofanate–methyl, (2) glyfosate or (3) untreated. The regrowth and occurrence of new infections were monitored.
In the same experiment, the effect of additional fytosanitary measures, removal of (a) plant debris and humus or (b) plant debris only, was compared to the effect of (c) leaving plant debris and humus on the soil surface. Soil samples were taken monthly at 20 cm depth and at soil surface and tested for the presence of P. ramorum, from July 2003 onwards. A baiting was used as test, using freshly picked leaves of Rhododendron catawbiense ‘Cunningham’s White’. This was followed by a real-time PCR assay to detect P. ramorum in the baiting material.
Two months after cutting back, development of new shoots
was observed in all objects. The lowest numbers were in the glyfosate
treated object. This regrowth indicates that the treatment was not effective.
A number of the new shoots was infected from the initial growth onwards
by P. ramorum. These infections proved that the remaining parts
of the stems were already infected. The different treatments had no influence
on the percentages infected shoots.
The results indicate that P. ramorum is
capable of surviving in sandy soil for at least one year. Furthermore,
in this experiment cutting back Rhododendron shrubs at 30 cm
was not sufficient.
| Coordinated by:
USDA Forest Service Pacific Southwest Research Station
University of California Integrated Hardwood Range Management Program,
Center for Forestry, Division of Agriculture and Natural Resources, and
California Oak Mortality Task Force
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