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 cinnamomi
Some chemical means of control include: fumigating and certain phosphonate fungistats. A tactic that may be effective, dependent on spores, would be fumigating before planting. However, this would not be effective for eradicating chlamydospores since they are present deeper down in the soil, so fumigation may not reach them. Some experts do not recommend fumigation as "P. cinnamomi" is often able to re-invade fumigated soil and could cause worse damage since the competing microorganisms in the soil microbial community may be reduced by fumigation. Phosphonate fungistats can improve the ability of a tree to tolerate, resist, or recover from disease by "Phytophthora cinnamomi". Phosphite has been used to limit the disease with some success and has been recognized as a major strategy for disease prevention. Phosphite is administered to plants through direct foliage sprays, aerial application by aircraft or through direct injection.