How pathogens can survive in aquatic environments

This article may give some insights into how P. ramorum can persist in a stream environment:

Islands of Germs: Researchers Discover Pathogens Floating on Tiny Clumps of Aquatic Detritus

Researchers have found evidence that "marine snow"--aggregates of organic material floating in water bodies--may act as microscopic, island-like refuges for pathogens, or disease-causing organisms. This detritus may skew water sampling procedures and mathematical models used to predict the transmission of waterborne diseases to humans.

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WSU stream monitoring program

The Washington State University, Puyallup (WSU-P) SOD community-based stream monitoring program was piloted in March 2010 in Washington's Puget Sound region. In addition to increasing the number of streams monitored for P. ramorum throughout the state by the Washington State Department of Agriculture (WSDA) and Washington Department of Natural Resources (WADNR), the new program also has potential to increase community awareness about the spread of P. ramorum and other Phytophthoras in streams. WSU-P received two years worth of funding from the USDA Forest Service to manage this program, which involves Master Gardeners, high school and college students, and other volunteers. Baiting sites were chosen based on discussions with WSDA and WADNR, and also volunteer availability. In 2010 four sites are being monitored for six two-week intervals and three sites for one two-week interval. The two-week interval sites are part of class projects for UW-Tacoma and Pierce College. Some students are also doing projects in the lab related to disinfectant use and survival in saline conditions. The program will be expanded in 2011. No P. ramorum has been detected at any of the sites so far. For more information, go to http://www.puyallup.wsu.edu/ppo/sod/monitoring/stream%20monitoring.htm or contact Marianne Elliott at melliott2@wsu.edu.

From the May COMTF newsletter

WSDA survey results

The Washington State Department of Agriculture (WSDA) has surveyed 30 host and non-host nurseries to date this year for P. ramorum, all of which have been negative for the pathogen. Some shippers in the state have greatly reduced the amount of high-risk genera (Camellia, Rhododendron, Pieris, Viburnum, and Kalmia) inventory for sale in an effort to reduce the risk of a P. ramorum find. However, two nurseries continue to yield positive water samples - one in Pierce County and one in King County. These sites continue to be monitored as no infected plants have been found in association with the positive water and the inoculum source is unknown. February and April surveys of plants downstream from the Pierce County positive nursery perimeter salal find in 2009 found no positive plants, and the Rosedale Stream has been continuously baited since January 2010, with no positive water finds. WSDA also followed up on trace-forward investigations from a Pennsylvania positive nursery, of which all 160 Laurus nobilis imported plants were free of P. ramorum.

From the May COMTF newsletter