Douglas-fir foliage retention dynamics across a gradient of Swiss needle cast in coastal Oregon and Washington

Swiss needle cast (SNC) is an important foliage disease of Douglas-fir (Pseudotsuga menziesii) caused by the native pathogen Nothophaeocryptopus gaeumannii, that has been present in epidemic proportions since the 1990s in coastal Douglas-fir forests. Under conducive environmental and stand conditions, the fungal fruiting bodies emerge on young needles, inhibiting gas exchange and causing premature needle casting and subsequent growth losses. Using a new regional plot network, which extends and approximately doubles the area of SNC-susceptible coastal forest sampled, we investigated the distribution of SNC disease indices across the region, and throughout individual tree crowns. Foliage retention varied from 1.15 to 3.9 years and disease severity (incidence x % occluded stomata) ranged from 0.05 to 52.11%. Foliage retention was positively correlated with distance from the coast and elevation. Foliage retention and disease severity were found to be negatively associated across the study area. Within crowns, disease severity was negatively associated with crown depth, and foliage retention was positively associated with crown depth, regardless of distance from coast. Across the entire study, foliage retention was found to decrease and disease severity increase with latitude, all else being equal. Tree growth metrics are positively associated with increasing foliage retention, and normal growth occurs greater than ~3.2 years.

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

Phytopathology ◽

10.1094/phyto.2003.93.7.790 ◽

2003 ◽

Vol 93 (7) ◽

pp. 790-798 ◽

Cited By ~ 32

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.

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Early genetic testing of coastal Douglas-fir for Swiss needle cast tolerance

Canadian Journal of Forest Research ◽

10.1139/x04-183 ◽

2005 ◽

Vol 35 (3) ◽

pp. 521-529 ◽

Cited By ~ 8

Author(s):

Fatih Temel ◽

G R Johnson ◽

W T Adams

Keyword(s):

Genetic Correlations ◽

Douglas Fir ◽

Seedling Stage ◽

Family Selection ◽

Mature Trees ◽

Individual Tree ◽

Needle Cast ◽

Swiss Needle Cast ◽

Early Testing ◽

Fungal Dna

The possibility of early testing coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) for Swiss needle cast (SNC; caused by Phaeocryptopus gaeumannii (Rohde) Petrak) tolerance was investigated using 55 Douglas-fir families from western Oregon. Seedlings were inoculated with P. gaeumannii naturally in the field and were visually scored for a variety of SNC symptom traits (i.e., needle and foliage color, and retention) at the seedling stage (age 2) and in "mature" (ages 10 and 12) trees at two test sites for both the seedling and mature ages. Seedlings were also assessed in the laboratory for SNC symptom traits, for proportion of needle stomata occluded with pseudothecia (PSOP), and for amount of P. gaeumannii DNA in needles. Although families differed significantly at both ages for all SNC symptom traits and for PSOP, they did not differ for amount of fungal DNA. Thus, genetic variation in SNC symptoms appears to be primarily due to differences in tolerance to the disease rather than to resistance to infection per se. Estimated individual-tree heritabilities for SNC symptom traits were low to moderate (mean hi2 = 0.19, range 0.060.37) at both ages, and within each age-class these traits were moderately to strongly genetically correlated (mean rA = 0.69, range 0.420.95). Type B genetic correlations between SNC symptom traits in seedlings and mature trees ranged from 0 to 0.83 and were weakest for traits measured in the laboratory. Genetic gain estimates indicated that family selection for SNC tolerance (i.e., greener needles or greater foliage retention) at the seedling stage can be very effective in increasing tolerance in older trees.

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Ten-year growth and mortality in young Douglas-fir stands experiencing a range in Swiss needle cast severity

Canadian Journal of Forest Research ◽

10.1139/x11-114 ◽

2011 ◽

Vol 41 (10) ◽

pp. 2064-2076 ◽

Cited By ~ 21

Author(s):

Douglas A. Maguire ◽

Douglas B. Mainwaring ◽

Alan Kanaskie

Keyword(s):

Disease Severity ◽

Growth Period ◽

Douglas Fir ◽

Permanent Plots ◽

Annual Increment ◽

Needle Age ◽

Needle Cast ◽

Needle Retention ◽

Swiss Needle Cast ◽

Annual Mortality

Swiss needle cast, a foliar disease caused by the Ascomycete Phaeocryptopus gaeumannii (T. Rohde) Petr., continues to afflict Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) in north coastal Oregon. Permanent plots were installed in 1998 to assess growth impacts and monitor disease severity. Gross periodic annual increment was measured for three 2-year growth periods and one 4-year growth period and ranged from 0.37 to 31.74 m3·ha–1·year–1. Foliage retention, defined as the average number of annual needle age classes held by a tree, was also estimated as an index of disease severity. Assuming negligible losses in stands with maximum needle retention (approximately 3.9 years), growth losses in net periodic annual increment reached slightly over 50% in stands with the lowest needle retention (approximately 1 year). Mixed-effects regression models supported a consistent relationship between foliage retention and both gross and net periodic annual increment among the four growth periods. Periodic annual mortality ranged from 0 to 19.12 m3·ha–1·year–1 but was not significantly influenced by Swiss needle cast as measured by average foliage retention. Minimum and maximum foliage retention has fluctuated annually from 1998 to 2008 on the permanent plots, but growth losses at a given level of foliage retention appear to have remained stable. Estimated growth losses are similar to those reported for comparable levels of defoliation by other agents.

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Growth responses to commercial thinning in Douglas-fir stands with varying severity of Swiss needle cast in Oregon, USA

Canadian Journal of Forest Research ◽

10.1139/x05-164 ◽

2005 ◽

Vol 35 (10) ◽

pp. 2394-2402 ◽

Cited By ~ 14

Author(s):

Douglas B Mainwaring ◽

Douglas A Maguire ◽

Alan Kanaskie ◽

Jeff Brandt

Keyword(s):

Basal Area ◽

Douglas Fir ◽

Growth Responses ◽

Infection Level ◽

Individual Tree ◽

Needle Cast ◽

Commercial Thinning ◽

Basal Area Growth ◽

Area Growth ◽

Swiss Needle Cast

Concern has risen about the degree to which Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands with severe infections of Swiss needle cast (SNC) respond to thinning. A retrospective study was established in the fall of 2001 to assess the growth of Douglas-fir stands that were commercially thinned between 4 and 10 years ago. Current SNC infection levels in these stands ranged from severe to very light. Past volume and basal area growth declined with increasing severity of SNC, as measured by current foliage retention and crown length / sapwood ratio. As has been observed in many other studies, thinning to lower residual stock reduced stand level growth; however, individual tree growth increased with lower residual stand density. The ratio of growth in successive periods and analysis of annual basal area growth since thinning suggested that trees did respond to thinning, although less so as SNC increased. A positive response to thinning, regardless of infection level, was confirmed by an analysis of annual trends in basal area growth over the first 5 years after thinning.

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Associations between Swiss Needle Cast Severity and Foliar Nutrients in Young-Growth Douglas-Fir in Coastal Western Oregon and Southwest Washington, USA

Forest Science ◽

10.1093/forsci/fxz022 ◽

2019 ◽

Vol 65 (5) ◽

pp. 537-542

Author(s):

Yung-Hsiang Lan ◽

David C Shaw ◽

Gabriela Ritóková ◽

Jeff A Hatten

Keyword(s):

Pacific Northwest ◽

Disease Incidence ◽

Douglas Fir ◽

Cooperative Research ◽

Foliar Nutrition ◽

Needle Cast ◽

The Pacific ◽

Foliage Nutrients ◽

Swiss Needle Cast ◽

Plot Network

Abstract Swiss needle cast (SNC) is a foliage disease of Douglas-fir (Pseudotsuga menziesii) caused by Nothophaeocryptopus gaeumannii, an ascomycete fungus (Mycosphaerellaceae) that causes tree growth reductions in the Pacific Northwest. The epidemiology of the fungus is generally well known, but the relations between disease expression and foliar nutrition are unclear. In this study, we used data from the Swiss Needle Cast Cooperative research and monitoring plot network in western Oregon and SW Washington to assess associations between SNC severity, carbon, and nine foliage nutrients (nitrogen, Na, K, P, Ca, Mg, Mn, Al, S). Foliage samples were collected from midcrown of selected Douglas-firs from each plot. SNC severity was determined on 2-year-old needles by multiplying disease incidence and fungal reproductive (pseudothecia) density. Disease severity and nutrient relations were determined using linear mixed models. SNC severity showed statistically significant positive trends with concentrations of carbon, nitrogen, Na, K, and S, no relation with concentrations of Ca, Mg, or Al, and slightly negative trends that were not significant for P and Mn. This is the first such analysis of associations between a conifer foliage disease and foliage nutrients across a landscape; subsequently, there is little published literature on how or why these nutrients may interact with disease.

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

Canadian Journal of Forest Research ◽

10.1139/cjfr-2013-0062 ◽

2013 ◽

Vol 43 (8) ◽

pp. 677-690 ◽

Cited By ~ 16

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.

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

Journal of Forestry ◽

10.1093/jofore/fvab011 ◽

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.

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

Canadian Journal of Forest Research ◽

10.1139/x06-044 ◽

2006 ◽

Vol 36 (6) ◽

pp. 1497-1508 ◽

Cited By ~ 17

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.

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