Spread of P. ramorum from nurseries into waterways-implications for pathogen establishment in new areas

In the United States, water and soil baiting have been part of the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA APHIS) Confirmed Nursery Protocol (CNP) to prevent the spread of Phytophthora ramorum from infected nursery stock since 2005. Additionally, the U.S. Department of Agriculture, Forest Service (USDA FS) has, since 2006, supported the national early detection stream baiting survey of forests and urban areas to monitor the potential spread of this pathogen from nurseries and other high-risk settings. These surveys have been conducted in cooperation with universities and state forestry agencies. As a result of these activities, P. ramorum has been detected in waterways at 10 sites in six states between 2006 and June 2009 (fig. 1). Below is a brief overview of these positive sites. Florida - In 2006 and 2007, P. ramorum was recovered from standing and flowing water inside, but not outside, a retail garden center where P. ramorum-positive plants were present. In February 2008, P. ramorum was recovered from a drainage ditch at a nearby production nursery that was associated with the garden center site. Then, in December 2008 and again in March 2009, the pathogen was detected in bait leaves deployed in a stream outside this nursery. Mississippi – P. ramorum was baited from a drainage ditch outside a nursery in December 2007. Subsequently, it was recovered from this ditch several times in 2008 and 2009 and a creek into which the ditch drains (using PCR on bait leaves) on multiple occasions from January 2008 through early 2009. Streamside vegetation surveys outside of the nursery resulted in PCR positives on two APHIS official host and associated host plant (HAP) (http://www.aphis.usda.gov/plant_health/plant_pest_info/pram/) samples in December 2007 and February 2008. To date, this is the only site where streamside vegetation surveys have detected P. ramorum on vegetation samples.