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 medicaginis
"P. medicaginis" is an water mould pathogen that causes root rot and damping off of seedlings. "P. medicaginis" is specific to alfalfa and chickpea and can reside in soil or water, but since it is a water mold, it requires free water to infect another plant. This disease is most prevalent in newly seeded fields that experience flooding but can also be found in mature plants. "P. medicaginis" commonly causes seedling death but if this pathogen is present in mature crops, "P. medicaginis" causes root rot which limits the plant’s ability to acquire nutrients and water. This leads to secondary symptoms such as chlorosis, wilting, stunting, root decay, lesions and death. This disease is difficult to identify but reddish-brown or black root lesions will exist and oospores, sporangia, zoospores, antheridia, and oogonia are spore types that will be visible under a microscope. An ELISA test can confirm the presence of "Phytophthora", but to confirm the species, a PCR test is effective. Several host factors will affect disease development including damage/stress to the plant and also the degree of resistance of host cultivar.