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 ramorum
Researchers have also developed numerous molecular techniques for "P. ramorum" identification. These include amplifying DNA sequences in the internal transcribed spacer region of the "P. ramorum" genome (ITS polymerase chain reaction, or ITS PCR); real-time PCR, in which DNA abundance is measured in real time during the PCR reaction, using dyes or probes such as SBYR-Green or TaqMan; multiplex PCR, which amplifies more than one region of DNA at the same time; and single strand conformation polymorphism (SSCP), which uses the ITS DNA sequence amplified by the PCR reaction to differentiate "Phytophthora" species according to their differential movement through a gel.