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
In 2009, the pathogen was found to be infecting and killing large numbers of Japanese larch trees ("Larix kaempferi") in the United Kingdom at sites in the English counties of Somerset, Devon, and Cornwall. It was the first time in the world that "Phytophthora ramorum" had been found infecting this species. Since then, it has also been found extensively in larch plantations in Wales and in southwest Scotland, leading to the deliberate felling of large areas. The UK Forestry Commission noted that eradication of the disease would not be possible, and instead adopted a strategy of containing the disease to reduce its spread. Symptoms of the disease on larch trees include dieback of the tree's crown and branches, and a distinctive yellowing or ginger colour beneath the bark. In August 2010, the disease was found in Japanese larch trees in Counties Waterford and Tipperary in Ireland. It had spread to Japanese larch plantations across the south of the country by February 2014. Coillte, who owned twenty forests where the disease was present, felled 16,000 trees in one of its forests, having already felled 150 hectares to contain the disease.