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 kernoviae
Since 2003, "Phytophthora kernoviae" has caused marked damage to ornamentals and species of trees in the Southwest United Kingdom. The oomycete pathogen was first discovered in the 1990s, yet only gained widespread attention when it was identified as one of the causal agents, along with "P. ramorum," of sudden oak death. Although the main concentration of this pathogen is primarily in South West England, its reach has extended to South Wales, Cheshire, and even further north into Scotland. Recently, this pathogen has been found on the steams and foliage of "Rhododendron", most significantly on "R. ponticum." Furthermore, the aggressive nature of "Phytophthora kernoviae" makes it an even more significant concern considering that the mainland of the UK has diverse ecosystems that are susceptible to the impact of this plant pathogen. From the "Rhododendron" host, infection is able to spread via the air to the bark of tree species, with the European beech tree ("Fagus sylvatica)" being especially susceptible. As of 2005, it was confined to a relatively small area of Cornwall but has also been found in Wales and Cheshire suggesting that the pathogen may be being spread by the horticultural trade. Due to the national and international demand of these plant products, "Phytophthora kernoviae" has initiated recent concern after being found "Vaccinium myrtillus", commonly called Bilberry. This pathogen causes significant necrosis on leaves, bleeding stem lesions, and stem dieback as the primary symptoms, which occur at an impressive rate. Countless species including "V. myrtillus", "V. vitis-idaea", "Arctostaphylos uva-ursi", and "Rhododendron ponticum" are all especially vulnerable to "P. kernoviae".