scholarly journals Persistence of the Swiss Needle Cast Outbreak in Oregon Coastal Douglas-Fir and New Insights from Research and Monitoring

2021 ◽  
Author(s):  
David C Shaw ◽  
Gabriela Ritóková ◽  
Yung-Hsiang Lan ◽  
Doug B Mainwaring ◽  
Andrew Russo ◽  
...  
Keyword(s):  
Climate Change ◽  
Regional Scale ◽  
Emerging Diseases ◽  
Douglas Fir ◽  
Landscape Patterns ◽  
Needle Cast ◽  
Plantation Management ◽  
Environmental Controls ◽  
Swiss Needle Cast ◽  
Improvement Programs

Abstract Swiss needle cast (SNC), caused by Nothophaeocryptopus gaeumannii, is a foliage disease of Douglas-fir (Pseudotsuga menziesii), that reduces growth in native stands and exotic plantations worldwide. An outbreak of SNC began in coastal Oregon in the mid-1990s and has persisted since that time. Here we review the current state of knowledge after 24 years of research and monitoring, with a focus on Oregon, although the disease is significant in coastal Washington and has recently emerged in southwestern British Columbia. We present new insights into SNC distribution, landscape patterns, disease epidemiology and ecology, host-pathogen interactions, trophic and hydrologic influences, and the challenges of Douglas-fir plantation management in the presence of the disease. In Oregon, the SNC outbreak has remained geographically contained but has intensified. Finally, we consider the implications of climate change and other recently emerged foliage diseases on the future of Douglas-fir plantation management. Study Implications: Douglas-fir tree growers need to consider Swiss needle cast (SNC) and other emerging foliage diseases as SNC has not abated over the past 24 years, and along with other emerging diseases, it continues to pose a threat to Douglas-fir plantation productivity. Douglas-fir management in western Oregon remains important, such that a knowledge of disease impacts and effective silvicultural responses is key. Managers should carefully consider whether alternative species may be ecologically or economically beneficial in some situations while tree improvement programs must continue to breed for tolerance to SNC. Research shows that regional scale foliage disease outbreaks can result in trophic cascades and hydrologic changes that affects more than just the trees. The environmental controls on the SNC epidemic imply that climate change could strongly influence future directions of the outbreak, with the greatest threats to trees at higher elevations.

Tree-ring analysis of the fungal disease Swiss needle cast in western Oregon coastal forests

2013 ◽  
Vol 43 (8) ◽  
pp. 677-690 ◽  
Author(s):  
E. Henry Lee ◽  
Peter A. Beedlow ◽  
Ronald S. Waschmann ◽  
Connie A. Burdick ◽  
David C. Shaw
Keyword(s):  
Climate Change ◽  
Disease Severity ◽  
Tree Ring ◽  
Summer Precipitation ◽  
Fungal Disease ◽  
Douglas Fir ◽  
Needle Cast ◽  
Introduced Range ◽  
Swiss Needle Cast ◽  
The Impact

Swiss needle cast (SNC), an important fungal disease of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), has increased in severity throughout its natural and introduced range over the last half century. The role of climate change and forest management practices in the increase is unclear. We analyzed tree-ring chronologies from six late-successional Douglas-fir stands in the western Oregon Coast Range using time-series intervention analysis (TSIA) to address how climate relates to the impact of SNC on tree growth. Tree-ring chronologies of western hemlock (Tsuga heterophylla (Raf.) Sarg.), a species not susceptible to the fungus Phaeocryptopus gaeumannii (Rhode) Petrak, were used as a climate proxy in the TSIA. We found that growth reductions associated with SNC dated back to the 1590s, the earliest record in our dendritic data. Growth reductions were synchronous across the six sites, indicating that the disease severity was largely influenced by climatic conditions. SNC impact peaked in 1984–1986 at all six study sites, followed by unprecedented disease impacts of 100% in 1996 and 2004 at one site, while decreasing to previous levels at the other five sites. Our SNC index of impact significantly correlated with winter and summer temperatures and summer precipitation. Winter conditions were more strongly associated with disease impact at wetter, cooler sites, whereas summer conditions were more important at less humid, warmer sites. With climate change, SNC impacts are likely to increase in coastal areas where June–July precipitation is much higher than the P. gaeumannii-limiting threshold of ∼110 mm, and decrease where summer precipitation is at or below the threshold. Warmer winters will increase disease severity at higher elevation, north along the coast from northern Oregon to British Columbia, and at inland sites where current winter temperatures limit fungal growth.

scholarly journals Predicting Swiss Needle Cast Disease Distribution and Severity in Young Douglas-Fir Plantations in Coastal Oregon

2003 ◽  
Vol 93 (7) ◽  
pp. 790-798 ◽  
Author(s):  
Pablo H. Rosso ◽  
Everett M. Hansen
Keyword(s):  
Prediction Model ◽  
Disease Severity ◽  
Pacific Northwest ◽  
Regression Tree ◽  
Douglas Fir ◽  
Slope Aspect ◽  
Disease Prediction ◽  
Needle Cast ◽  
Swiss Needle Cast ◽  
The Relationship

Swiss needle cast (SNC), caused by the fungus Phaeocryptopus gaeumannii, is producing extensive defoliation and growth reduction in Douglas-fir forest plantations along the Pacific Northwest coast. An SNC disease prediction model for the coastal area of Oregon was built by establishing the relationship between the distribution of disease and the environment. A ground-based disease survey (220 plots) was used to study this relationship. Two types of regression approaches, multiple linear regression and regression tree, were used to study the relationship between disease severity and climate, topography, soil, and forest stand characteristics. Fog occurrence, precipitation, temperature, elevation, and slope aspect were the variables that contributed to explain most of the variability in disease severity, as indicated by both the multiple regression (r 2 = 0.57) and regression tree (RMD = 0.27) analyses. The resulting regression model was used to construct a disease prediction map. Findings agree with and formalize our previous understanding of the ecology of SNC: warmer and wetter conditions, provided that summer temperatures are relatively low, appear to increase disease severity. Both regression approaches have characteristics that can be useful in helping to improve our understanding of the ecology of SNC. The prediction model is able to produce a continuous prediction surface, suitable for hypothesis testing and assisting in disease management and research.

Influence of Swiss needle cast on foliage age-class structure and vertical foliage distribution in Douglas-fir plantations in north coastal Oregon

2006 ◽  
Vol 36 (6) ◽  
pp. 1497-1508 ◽  
Author(s):  
Aaron R Weiskittel ◽  
Douglas A Maguire ◽  
Sean M Garber ◽  
Alan Kanaskie
Keyword(s):  
Vertical Distribution ◽  
Douglas Fir ◽  
Parameter Estimates ◽  
Class Structure ◽  
Needle Cast ◽  
Age Class ◽  
Relative Contribution ◽  
Crown Structure ◽  
Growth Decline ◽  
Swiss Needle Cast

Swiss needle cast (SNC) causes premature loss of foliage and subsequent growth decline in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Although the mechanisms leading to this growth decline include loss of photosynthetic surface area and physiological disruption of surviving foliage, estimating the relative contribution of these two primary sources requires precise quantification of SNC effects on total foliage mass, foliage age-class structure, and vertical foliage distribution. The effect of SNC severity on these crown structural attributes was tested across a range of stand densities and site qualities in 10- to 60-year-old plantations in north coastal Oregon. Foliage mass in each age-class was sampled at the branch level, and the resulting equations were applied to all live branches on intensively measured sample trees. Vertical distribution of each foliage age-class was described by a beta distribution fitted to each sample tree, and sources of variation in vertical distribution were tested by regressing beta parameter estimates on SNC intensity and other covariates representing tree, stand, and site attributes. Distribution of foliage mass by age-class and by relative height in the crown was significantly affected by SNC severity, in addition to other covariates such as crown size and tree social position. SNC caused a reduction in the amount of foliage in each age-class and greater relative representation of younger needles. SNC also shifted the mode of relative vertical distribution toward the top of the tree for the three youngest foliage age-classes, but toward the base of the crown for 4- and 5-year-old foliage. Quantification of foliage age-class structure and vertical distribution across a range of SNC severity has helped to establish diagnostic criteria for assessing changes in crown structure that precede declines in growth and vigor. The induced changes in crown structure will also help to identify the relative contribution of several mechanisms causing growth losses in diseased trees.

scholarly journals Incidence and Impact of Swiss Needle Cast in Forest Plantations of Douglas-fir in Coastal Oregon

Plant Disease ◽  
2000 ◽  
Vol 84 (7) ◽  
pp. 773-778 ◽  
Author(s):  
E. M. Hansen ◽  
J. K. Stone ◽  
B. R. Capitano ◽  
P. Rosso ◽  
W. Sutton ◽  
...  
Keyword(s):  
Severe Disease ◽  
Tree Height ◽  
Aerial Survey ◽  
Douglas Fir ◽  
Permanent Plots ◽  
Forest Plantations ◽  
Needle Age ◽  
Needle Cast ◽  
Needle Retention ◽  
Swiss Needle Cast

An epidemic of Swiss needle cast, caused by the ascomycete Phaeocryptopus gaeumannii, is causing defoliation and growth reductions in Douglas-fir forest plantations along the Oregon Coast. The area of symptomatic plantations has been monitored annually since 1996 by aerial survey; in spring 1999, 119,500 ha were affected. Pathogen and symptom development have also been monitored on nine permanent plots in stands of differing disease severity. Infection levels and symptom severity are greatest in low elevation plantations close to the coast. In areas of severe disease, trees retain only current year needles. Defoliation is proportional to the number of stomata occluded by pseudothecia of the fungus, with needles being shed when about 50% of stomata are occupied, regardless of needle age. Fungus sporulation and premature needle abscission are greatest on the upper branches of trees. Annual application of fungicides increases needle retention significantly. Tree height and diameter growth and total tree volume are reduced by disease, and tree volume is significantly correlated with needle retention on our plot trees. The epidemic continues to be most severe in Douglas-fir plantations established on sites where Sitka spruce and western hemlock or red alder predominated in earlier times.

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