Phytophthora ramorum
Detection of "P. ramorum" in watercourses has emerged as the earliest of early detection methods. This technique employs pear or rhododendron baits suspended in the watercourse using ropes, buckets, mesh bags, or other similar devices. If plants in the watershed are infected with "P. ramorum", zoospores of the pathogen (as well as other "Phytophthora" spp.) are likely present in adjacent waterways. Under conducive weather conditions, the zoospores are attracted to the baits and infect them, causing lesions that can be isolated to culture the pathogen or analyzed via PCR assay. This method has detected "P. ramorum" at scales ranging from small, intermittent seasonal drainages to the Garcia, Chetco, and South Fork Eel Rivers in California and Oregon (144, 352, and 689 mi2 drainage areas, respectively). It can detect the existence of infected plants in watersheds before any mortality from the infections becomes evident. Of course, it cannot detect the exact locations of those infected plants: at the first sign of "P. ramorum" propagules in the stream, crews must scour the watershed using all available means to find symptomatic vegetation.
Phytophthora tentaculata
Phytophthora tentaculata is a plant pathogen that causes root and stalk rot. It was first isolated in 1993 in a nursery in Germany infecting "Chrysanthemum", "Verbena", and "Delphinium ajacis". It has since been found infecting a "Verbena" in Majorca, Spain in June 2001 but was thought to be restricted to nurseries in Germany and the Netherlands. Other species have since been found to be infected, "Santolina chamaecyparissus" (Lavender cotton) in Spain in 2004, "Gerbera jamesonii" in Italy 2006, and "Aucklandia lappa" in China in 2008.