Swiss Needle Cast in Western Oregon Douglas-Fir Plantations: 20‐Year Monitoring Results

Gabriela Ritóková,Danny Norlander,John Browning,Alan Kanaskie,Greg Filip,David Shaw

doi:10.3390/f7080155

Gabriela Ritóková, Danny Norlander + Show 4 more

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https://doi.org/10.3390/f7080155

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Abstract

Swiss needle cast (SNC), a foliar disease specific to Douglas-fir (Pseudotsuga menziesii), is caused by an endemic Ascomycete fungus (Phaeocryptopus gaeumannii). In the late 1980s and early 1990s significant symptoms began to appear in coastal Oregon, and these have been associated with the planting of Douglas-fir in the Sitka spruce zone, leaf wetness during potential spore dispersal in May–August, and mild winter temperature. The first annual aerial survey was initiated in 1996 and has continued through 2015, which indicates a significant increase in area of visible symptoms from the air, increasing from 53,050 ha in 1996 to 238,705 ha in 2015. Monitoring plots in the NW Oregon Coast Range verified impacts of SNC on tree growth and productivity, with growth reductions averaging about 23% in the epidemic area linked to needle retention. A series of monitoring plots was set up in the western Cascade Mountains of Oregon and 590 10–23-year old Douglas-fir trees in 59 stands were tracked for 10 years, measured in 2001, 2006, and 2011. No measureable growth impacts were noted in this region of Oregon. A new plot network is being installed throughout the Oregon and southwest Washington coastal ranges as a means of monitoring future disease impact and providing framework for additional studies.

Highlights

Swiss needle cast (SNC), caused by the ascomycete fungus, Phaeocryptopus gaeumannii (Rodhe)Petrak, is the most damaging foliage disease of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) in the Pacific Northwest [1,2,3]
The fungus is native to western North America, and is common wherever the host tree is grown. It is known as Swiss needle cast because the disease was first noticed in Switzerland and Germany where Douglas-fir was planted in the early 20th Century
Our objectives are to report on the 20 years of SNC aerial monitoring and 10-year plot monitoring in the Cascade Mountains, both aimed at assessing the threat to Douglas-fir forests in western Oregon, USA

Summary

Introduction

Swiss needle cast (SNC), caused by the ascomycete fungus, Phaeocryptopus gaeumannii (Rodhe)Petrak, is the most damaging foliage disease of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) in the Pacific Northwest [1,2,3]. Swiss needle cast (SNC), caused by the ascomycete fungus, Phaeocryptopus gaeumannii (Rodhe). Petrak, is the most damaging foliage disease of coastal Douglas-fir The fungus is native to western North America, and is common wherever the host tree is grown. It is known as Swiss needle cast because the disease was first noticed in Switzerland and Germany where Douglas-fir was planted in the early 20th Century. Americans subsequently checked native Douglas-fir stands, the fungus was common, but apparently caused no disease [4]. In the 1970’s and 1980’s the disease emerged in Christmas tree plantations in Oregon and Washington, and in the 1980’s and 1990’s became noticeable in forest plantations along the Pacific Coast. The disease intensified to the point that private forestland owners, federal and state agencies, in concert with Oregon State University together formed the Swiss Needle

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