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Abstract
For more than a decade, the Rizzo lab and collaborators have monitored northern and central coastal California watersheds each spring and early summer for the presence of
Phytophthora using submerged
Rhododendron leaves as bait. This served as an early detection tool for the sudden oak death (SOD) pathogen,
P. ramorum, but other species of
Phytophthora were encountered and notable isolates occasionally saved; in recent years a more concerted effort was made to isolate species of
Phytophthora other than
ramorum. Twenty-three species were identified using a combination of morphological traits and ITS nrDNA sequences. Three provisional taxa, taxon mendostream (a novel member of
Phytophthora clade 9), taxon obispostream (a member of the
P. citricola species complex) and taxon sequoiasoil (a close relative of
P. cactorum) are introduced based on unique ITS, mtCOX1 and mtCOX2 sequences. Due to the ongoing SOD epidemic, the exotic, invasive
P. ramorum was the most common species isolated, followed by members of
Phytophthora clades 3 and 6. This is consistent with studies performed in Alaska and Oregon, suggesting that many of these species are native to the area. Maps of infested watersheds are presented, spanning more than 750 km of the California coast.
Parent Publication
Citation
Bourret, Tyler B.; Mehl, Heather K.; Aram, Kamyar; Rizzo, David M. 2017.
Rhododendron leaf baiting of coastal California watersheds for
Phytophthora. In: Frankel, Susan J.; Harrell, Katharine M., tech. coords. Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 63.
