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.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 89 • No. 1