01803nas a2200157 4500008004100000245008500041210006900126300001600195490000700211520131200218100001401530700001601544700002001560700001901580856004601599 2009 eng d00aStream monitoring for detection of Phytophthora ramorum in Oregon tanoak forests0 aStream monitoring for detection of Phytophthora ramorum in Orego a1182–11860 v933 a

Stream monitoring using leaf baits for early detection of Phytophthora ramorum has been an important part of the Oregon Sudden Oak Death (SOD) program since 2002. Sixty-four streams in and near the Oregon quarantine area in the southwest corner of the state were monitored in 2008. Leaves of rhododendron (Rhododendron macrophyllum) and tanoak (Lithocarpus densiflorus) were placed in mesh bags, and bags were floated in streams. Leaf baits were exchanged every 2 weeks throughout the year. Leaves were assayed by isolation on selective medium and by multiplex rDNA internal transcribed spacer polymerase chain reaction (ITS PCR). The two methods gave comparable results, but multiplex PCR was more sensitive. P. ramorum was regularly recovered at all seasons of the year from streams draining infested sites 5 years after eradication treatment. In streams with lower inoculum densities, recovery was much higher in summer than in winter. P. ramorum was isolated from streams in 23 watersheds. When P. ramorum was detected, intensive ground surveys located infected tanoaks or other host plants an average of 306 m upstream from the bait station. P. ramorum was isolated from stream baits up to 1,091 m from the probable inoculum source.

1 aSutton, W1 aHansen, E M1 aReeser, Paul, W1 aKanaskie, Alan uhttp://dx.doi.org/10.1094/PDIS-93-11-1182