03635nas a2200121 4500008004100000245007400041210006900115260001200184490001000196520325300206100001603459856003803475 2013 eng d00aPhytophthora species and riparian alder tree damage in western Oregon0 aPhytophthora species and riparian alder tree damage in western O c02/20140 vPh.D.3 a

The genus Phytophthora contains some of the most destructive pathogens of forest trees, including the most destructive pathogen of alder in recent times, Phytophthora alni. Alder trees were reported to be suffering from canopy dieback in riparian ecosystems in western Oregon, which prompted a survey of alder health and monitoring for P. alni. In 2010 surveys in western Oregon riparian ecosystems were initiated to gather baseline data on damage and on the Phytophthora species associated with alder. Damage was recorded and analyzed from transects containing alder trees with canopy dieback symptoms according to damage type: (1) pathogen, (2) insect, or (3) wound. Phytophthora species from western Oregon riparian ecosystems were systematically sampled, isolated, identified, stored and compared. Koch's Postulates were evaluated for three key Phytophthora species recovered: P. alni, P. siskiyouensis and P. taxon Oaksoil, and alder disease in the western United States was described. Then, the ecological role of the most abundant Phytophthora species from streams was evaluated. The data indicated that many of the same agents reported causing damage to alder trees in the western United States were also damaging alder trees in western Oregon including the alder flea beetle, sawflies, flood debris, Septoria alnifolia, and Mycopappus alni. The most important damage correlated with canopy dieback was incidence of Phytophthora cankers, and isolation of Phytophthora siskiyouensis. In the initial systematic survey of Phytophthora species, 1190 individual Phytophthora isolates were recovered but were of many different species. In the survey of alder roots, P. alni subsp. uniformis was one of the species recovered from necrotic red alder roots, but overall incidence was low; it was isolated four times. From the evaluation of Koch's postulates, Phytophthora canker of alder in the western United States was described, and is a bole canker caused by Phytophthora. Phytophthora canker of alder was only found caused by P. siskiyouensis in nature, and it was isolated 74 times. Isolation was mainly from bole cankers and diseased roots on red and white alder, and from water and alder leaf debris floating in the stream. The most abundant Phytophthora species associated with red alder is an informally described species P. taxon Oaksoil, which appears to be a relatively benign aquatic saprotroph of alder leaf debris. Canopy dieback was more prevalent in riparian alder trees from transects with P. siskiyouensis than from transects with P. taxon Oaksoil but without P. siskiyouensis (70% and 35%, respectively). The informally described P. taxon Oaksoil from western Oregon is formally described here as P. obrutafolium sp. nov., closely related to P. bilorbang from western Australia, and P. taxon Oaksoil ss from an oak forest in France. In summary, other agents besides Phytophthora can damage alder trees in western Oregon. Many Phytophthora species associate with alder in western Oregon but not all of them are important damaging agents of alder. However, Phytophthora canker of alder is widespread in western Oregon. In the United States, Phytophthora canker of alder has only been found to be caused by P. siskiyouensis.

1 aSims, Laura uhttp://hdl.handle.net/1957/46441 02235nas a2200181 4500008004100000022001400041245007400055210006900129260001600198300001200214490000700226520169600233100001601929700001801945700001901963700002001982856005102002 2015 eng d a0029-344X00aAlder Canopy Dieback and Damage in Western Oregon Riparian Ecosystems0 aAlder Canopy Dieback and Damage in Western Oregon Riparian Ecosy cJan-01-2015 a34 - 460 v893 a

We gathered baseline data to assess alder tree damage in western Oregon riparian ecosystems. We sought to determine if Phytophthora-type cankers found in Europe or the pathogen Phytophthora alni subsp. alni, which represent a major threat to alder forests in the Pacific Northwest, were present in the study area. Damage was evaluated in 88 transects; information was recorded on damage type (pathogen, insect or wound) and damage location. We evaluated 1445 red alder (Alnus rubra), 682 white alder (Alnus rhombifolia) and 181 thinleaf alder (Alnus incana spp. tenuifolia) trees. We tested the correlation between canopy dieback and canker symptoms because canopy dieback is an important symptom of Phytophthora disease of alder in Europe. We calculated the odds that alder canopy dieback was associated with Phytophthora-type cankers or other biotic cankers. P. alni subsp. alni (the causal agent of alder disease in Europe) was not identified in western Oregon; however, Phytophthora siskiyouensis was isolated from Phytophthora-type cankers which were present on 2% of red alder trees and 3% of white alder trees. The odds of canopy dieback were 5.4 and 4.8 times greater for red and white alder (respectively) with Phytophthora-type canker symptoms than in trees without such cankers. The percentage of trees with canopy dieback was 51%, 32%, and 10% for red, white, and thinleaf alder respectively. Other common damage included wounding, foliar pathogens and insects on red alder. This is the first report of Phytophthora canker of alder in United States forests and first report of P. siskiyouensis isolation from alder in forests anywhere.

1 aSims, Laura1 aGoheen, Ellen1 aKanaskie, Alan1 aHansen, Everett uhttp://www.bioone.org/doi/10.3955/046.089.0103