Appendix I. Water Sampling Protocol
Revised March 2010
See http://www.aphis.usda.gov/plant_health/plant_pest_info/pram/ for latest approved
Phytophthora ramorum is a soil-borne plant pathogen well adapted to water-logged soil
environments. Described as a “water mold”, P. ramorum is more closely related to algae than
fungi. For this reason, water samples collected from potentially infested nursery blocks can be
tested for the presence of P. ramorum spores.
The following methods should be utilized to detect P. ramorum on a landscape or watershed
level. A detection of P. ramorum does not mean that nursery stock is infected with the
pathogen, but that an infestation within the watershed exists. Detection of P. ramorum by this
method indicates a problem exists, thereby triggering a more intensive survey.
There are two methods summarized here for detecting Phytophthora species spores from water.
Additional updates to this protocol are expected soon. The first and preferred sample collection
method, for use in waterways or ponds located within and around a nursery, relies on host
material (Rhododendron, Camellia, etc.) leaves contained in mesh bags or containers that
function to “bait” or attract Phytopththora spores. This method is most effective when water
temperatures are warmer than 39oF but cooler than summer-heated levels. After exposure, leaf
baits are held briefly in a moist chamber to promote disease development and symptom
The second method, water filtration, may be used where drainage outflows, diversion boxes,
standing water and streams are found within the nursery perimeter. More time-sensitive than the
first method, water is collected in one-liter plastic bottles and filtered through sterile particulate
filters. Following exposure, filters are placed on specialized growth media to support pathogen
In situ Water Sampling with Host Material Leaf Baits
• Collect leaves that are known to be free of disease from a p