scholarly journals Transformation of western hemlock ( Tsuga heterophylla ) tree crowns by dwarf mistletoe ( Arceuthobium tsugense , Viscaceae)

2020 ◽  
Author(s):  
Stephen J. Calkins ◽  
David C. Shaw ◽  
Yung‐Hsiang Lan
Keyword(s):  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Dwarf Mistletoe ◽  
Tree Crowns

Spatial and population characteristics of dwarf mistletoe infected trees in an old-growth Douglas-fir – western hemlock forest

2005 ◽  
Vol 35 (4) ◽  
pp. 990-1001 ◽  
Author(s):  
David C Shaw ◽  
Jiquan Chen ◽  
Elizabeth A Freeman ◽  
David M Braun
Keyword(s):  
Nearest Neighbor ◽  
Positive Association ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Negative Association ◽  
Population Characteristics ◽  
Western Hemlock ◽  
Silver Fir ◽  
Dwarf Mistletoe ◽  
Old Growth

We investigated the distribution and severity of trees infected with western hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahl) G.N. Jones subsp. tsugense) in an old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) – western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest. With the use of Hawksworth six-class dwarf mistletoe rating system, infection status was assessed for 3516 hemlock and true firs ≥5 cm diameter on a 12-ha stem-mapped plot located in the Cascade Mountains of southwest Washington State. Within the plot, 33% of the area had some level of infection and 25% (719) of western hemlocks, 2.2% (12) of Pacific silver fir (Abies amabilis (Dougl.) Forbes), and 29% (2) of noble fir (Abies procera Rehd.) trees were infected. Infected trees are larger than uninfected trees, on average, and within the infected tree population, the severely infected trees averaged larger than lightly infected trees. Abundant dwarf mistletoe in larger trees definitely positions the dwarf mistletoe population for future spread. Ripley's K analysis indicates a negative association between infected and uninfected hemlock trees, confirming that the infected trees form distinct dwarf mistletoe infection centers. The infection centers are actively spreading at their margins, which was confirmed by nearest neighbor analysis. Heavily infected trees had a negative association with uninfected trees, while lightly infected trees had a positive association with uninfected trees.

scholarly journals First Report of Colletotrichum gloeosporioides on Arceuthobium tsugense subsp. tsugense in Canada

Plant Disease ◽  
1997 ◽  
Vol 81 (9) ◽  
pp. 1095-1095 ◽  
Author(s):  
H. H. Kope ◽  
S. F. Shamoun ◽  
C. Oleskevich
Keyword(s):  
Colletotrichum Gloeosporioides ◽  
Control Measure ◽  
Personal Communication ◽  
First Record ◽  
Colony Growth ◽  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Dwarf Mistletoe ◽  
The Pacific ◽  
Pure Cultures

Although reports of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz. occurring as a hyperparasite of western hemlock dwarf mistletoe (Arceuthobium tsugense (Rosend.) G.N. Jones subsp. tsugense) have been previously published (1), there are no collection or herbarium records to support this finding (B. Geils, personal communication). Given this ambiguity, this report is the first record of C. gloeosporioides on A. tsugense subsp. tsugense based on voucher collections deposited at the Pacific Forestry Centre (DAVFP #25277). Western hemlock dwarf mistletoe is a parasitic plant that occurs on western hemlock (Tsuga heterophylla (Raf.) Sarg.), causing growth reduction, degradation of merchantable wood, and reduction in reproductive fitness of its host. Dwarf mistletoe infections result in significant reduction in volume of mature stands of T. heterophylla in coastal British Columbia (B.C.). Aside from traditional silvicultural control methods, a potentially important control includes the use of fungi deleterious to the growth of dwarf mistletoe. C. gloeosporioides has been identified as a hyperparasite of numerous Arceuthobium spp., including A.tsugense subsp. mertensiana Hawksworth & Nickrent (1). In October 1996 and May 1997, lesions were observed on shoots of A. tsugense subsp. tsugense collected from two field sites, Cowichan Lake (48°56′N, 124°23′W) and Duncan (48°45′N, 123°50′W), B.C. Acervuli containing masses of spores and dark setae were observed within lesions, and conidia from the acervuli produced pure cultures of C. gloeosporioides. The fungus was identified based on conidial and cultural characteristics (2). Conidia were cylindrical to elliptical in shape and measured 12.5 to 15.0 × 2.5 to 4.0 μm. On potato dextrose agar, colonies developed a white to patchy, dark gray mycelial mat with conidia produced in mycelia and in distinct salmon-colored masses. Colony growth occurred at 10 to 30°C, with optimum growth at 20°C, while maximum germination was observed at 30°C after 24 h, with germination occurring between 10 and 35°C. Branches with healthy mistletoe shoots were cut from western hemlock trees and placed in Hoagland's nutrient solution. A spore suspension (106 conidia per ml) was brushed onto mistletoe shoots at a rate of approximately 1 ml per replicate, with 8 to 10 replicate branches, each containing a cluster of >5 shoots. Controls were treated with sterile, distilled water and branches were incubated in the greenhouse with 55% relative humidity. The fungus was re-isolated from acervuli that developed on inoculated shoots after 14 days, and these results were repeated in a second experiment. The fungus was not isolated from the controls. Koch's postulates were fulfilled by inoculating shoots of A. tsugense subsp. tsugense and re-isolating the pathogen from symptomatic stems. C. gloeosporioides could be an important control measure for western hemlock dwarf mistletoe. References: (1) F. G. Hawksworth and D. Weins. 1996. Agric. Handb. 709, USDA, Forest Service, Washington, D.C. (2) B. C. Sutton. 1980. The Coelomycetes. Commonw. Mycol. Inst., Kew, England.

Modeling the incidence and severity of hemlock dwarf mistletoe in 110-year-old wind-disturbed forests in Southeast Alaska

1998 ◽  
Vol 28 (10) ◽  
pp. 1501-1508 ◽  
Author(s):  
L M Trummer ◽  
P E Hennon ◽  
E M Hansen ◽  
P S Muir
Keyword(s):  
Basal Area ◽  
Tsuga Heterophylla ◽  
Picea Sitchensis ◽  
Western Hemlock ◽  
Managed Forests ◽  
Coastal Forests ◽  
Dwarf Mistletoe ◽  
Infection Level ◽  
Southeast Alaska ◽  
Preliminary Validation

Amodel was developed to predict the severity of dwarf mistletoe (Arceuthobium tsugense (Rosendahl) G.N. Jones) in western hemlock trees (Tsuga heterophylla (Raf.) Sarg.) that developed within forests of Southeast Alaska that experienced near-catastrophic windthrow in the late 1800s. The model suggests that the degree of dwarf mistletoe severity on western hemlock trees was significantly and positively correlated with levels of dwarf mistletoe infection and basal area (m2/ha) in large and small residual trees that survived the wind disturbance. No significant relationships were found between severity level and any other factors, including site productivity, density of coexisting Sitka spruce (Picea sitchensis (Bong.) Carr.), or slope. The model demonstrates the overriding importance of infected residual trees to predict future severity of dwarf mistletoe; greater size and infection level of residual trees results in greater dwarf mistletoe levels on regenerating hemlock crop trees. The model, derived from 76 plots on Kuiu Island, was tested in 18 plots on Chichagof Island, providing a preliminary validation. Slower rates of dwarf mistletoe spread and intensification in forests of southeastern Alaska, as compared with similar coastal forests south of Alaska, provide an opportunity for managers to manipulate the parasite to desired levels in managed forests.

BARK MOISTURE RELATIONSHIPS IN WESTERN HEMLOCK BRANCHES INFECTED BY DWARF MISTLETOE

1964 ◽  
Vol 42 (10) ◽  
pp. 1313-1319 ◽  
Author(s):  
J. A. Baranyay
Keyword(s):  
Moisture Content ◽  
Sampling Period ◽  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Dwarf Mistletoe ◽  
Parasitic Fungi ◽  
The Poor ◽  
Good Site ◽  
Time Of Year ◽  
Poor Site

Investigations of bark moisture in branches of western hemlock, Tsuga heterophylla (Raf.) Sargent, infected by western dwarf mistletoe, Arceuthobium campylopodum Engelm. forma tsugensis Gill, were carried out in good and poor growing sites on the Campus Forest and Research Forest, respectively, of the University of British Columbia. Bark moisture was determined in terms of relative turgidity.Major changes in the moisture content of non-invaded bark occurred in both sites, but the changes were more pronounced in the poor site than in the good site. The relative turgidities of non-invaded bark were less than 80% for 5.9% of the sampling period, June to February inclusive, in the good site, and for 33.3% of the time in the poor site. Bark moistures were more sensitive to changes of precipitation and temperature in the poor site than in the good site, because of the shallow rooting habit of trees and the propensity of the soil in this site to drought.Dwarf mistletoe did not affect bark moisture in the non-invaded portions of branches, but the moisture content of invaded bark was variously affected depending upon the season of year and the age of the infection. When bark moistures were generally low, for example, in April in the good site and June in the poor site, the moisture content of bark that had been invaded for less than 10 years was highest at the centers of infections and lowest at the periphery. At the same time of year but in bark that had been invaded for more than 10 years, the moisture content was highest at the periphery of infections while at the centers it was similarly low to that of the non-invaded bark of the same branches. When bark moistures were generally high, for example, in July in the good site and early August in the poor site, the moisture content of bark in the young infections remained high throughout the entire invaded area. At the same time of year but in the old infections, bark moisture was lowest at the center of infections, and at these times the only portion of an infected branch having a bark moisture content of less than 80% relative turgidity was the center of infection. This may explain the successful establishment of parasitic fungi at these locations.

Potebniamyces gallicola n.sp., from dwarf mistletoe infections in western hemlock

1981 ◽  
Vol 59 (9) ◽  
pp. 1610-1612 ◽  
Author(s):  
A. Funk ◽  
R. B. Smith
Keyword(s):  
British Columbia ◽  
Tsuga Heterophylla ◽  
Western Hemlock ◽  
Dwarf Mistletoe

Potebniamyces gallicola n.sp. is described from dwarf mistletoe galls (Arceuthobium tsugense (Rosendahl) G. N. Jones) on western hemlock (Tsuga heterophylla (Raf.) Sarg.), growing in British Columbia, Canada. It has a typical Phacidiopycnis anamorph which is produced both in the host and in culture, as well as hyphal "bud" conidia produced in fresh agar cultures.

scholarly journals Evaluating the Accuracy of Ground-Based Hemlock Dwarf Mistletoe Rating: A Case Study Using the Wind River Canopy Crane

2000 ◽  
Vol 15 (1) ◽  
pp. 8-14 ◽  
Author(s):  
David Shaw ◽  
Elizabeth A. Freeman ◽  
Robert L. Mathiasen
Keyword(s):  
Rating System ◽  
Western Hemlock ◽  
Timber Management ◽  
Research Facility ◽  
Dwarf Mistletoe ◽  
Individual Tree ◽  
Tree Crowns ◽  
Organic Debris ◽  
The Individual

Abstract The accuracy of ground based estimates using the six-class dwarf mistletoe rating system was evaluated in an old-growth Douglas-fir/western hemlock forest by comparing ground ratings by five different observers to an examination of tree crowns from a construction crane at the Wind River Canopy Crane Research Facility, Washington. A total of 139 dominant, codominant, and intermediate western hemlock were evaluated. No consistent pattern emerged to indicate where overall error was made. All but one observer was relatively accurate at identifying noninfected trees (73 to 95% noninfected trees accurately rated by four observers). However, the observers were less accurate at estimating the DMR class of the infected trees (11% to 3 7% of the infected trees accurately rated), including a number of trees incorrectly rated by two or more DMR classes. One observer rated 98% of the trees as having infections, while the crane survey estimated only 53% of the trees as having infections. Each observer divided the individual tree crowns into thirds and estimated infections based on summing lower, middle, and upper canopy levels. There was no pattern to the errors associated with estimates by canopy level. One observer significantly overestimated all canopy levels, one observer estimated all accurately, one observer significantly underestimated all canopy levels, one observer underestimated the mid and upper canopies, and one observer underestimated the lower and upper canopies. The principal reasons for inaccurate dwarf mistletoe ratings were assumed to be difficulty in accurately estimating crown thirds, misidentification of infections because of various stem deformities or accumulation of organic debris resembling infections, and the difficulty in observing infections high above the ground and through dense vegetation. Only one of the five observers accurately represented the spatial pattern of the infection center. The implications of this research vary depending on whether the results are to be used for timber management or for research and modeling applications. West. J. Appl. For. 15(1):8-14.

scholarly journals Comparative Susceptibility of Conifers to Western Hemlock Dwarf Mistletoe in the Cascade Mountains of Washington and Oregon

2005 ◽  
Vol 20 (2) ◽  
pp. 94-100 ◽  
Author(s):  
Robert L. Mathiasen ◽  
Carolyn M. Daugherty
Keyword(s):  
Pacific Northwest ◽  
Tsuga Heterophylla ◽  
Host Susceptibility ◽  
Western Hemlock ◽  
Silver Fir ◽  
Mixed Conifer ◽  
Dwarf Mistletoe ◽  
Resource Managers ◽  
Abies Procera ◽  
Live Tree

Abstract A total of 24 mixed conifer stands in Washington and Oregon infested with western hemlock dwarf mistletoe (Arceuthobium tsugense subsp. tsugense) were sampled to compare host susceptibility to this parasitic plant. Temporary circular plots were established around dominant, severely infected western hemlocks (Tsuga heterophylla). Within plots, species, diameter at breast height, and dwarf mistletoe rating (6-class system) were determined for each live tree. More than 5,700 trees were sampled in 275 plots. Based on the incidence of infection, tree species were assigned to host susceptibility classes. Western hemlock is classified as the only principal host of western hemlock dwarf mistletoe. Pacific silver fir (Abies amabilis), noble fir (Abies procera), and mountain hemlock (Tsuga mertensiana) are classified as occasional hosts. Resource managers can use the host susceptibility classifications based on this study for decisions regarding which trees to retain when selectively harvesting mixed conifer stands infested with western hemlock dwarf mistletoe in the Pacific Northwest. West. J. Appl. For. 20(2):94–100.

Growth ofPseudotsuga menziesiiandTsuga heterophyllaseedlings along a light gradient: resource allocation and morphological acclimation

1997 ◽  
Vol 75 (9) ◽  
pp. 1424-1435 ◽  
Author(s):  
D. Mailly ◽  
J. P. Kimmins
Keyword(s):  
Leaf Morphology ◽  
Biomass Accumulation ◽  
Tsuga Heterophylla ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Low Light ◽  
Growing Seasons ◽  
Light Levels ◽  
Light Gradient ◽  
Relative Light Intensity

Silvicultural alternatives that differ in the degree of overstory removal may create shady environments that will be problematic for the regeneration of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Gradients of light in the field were used to compare mortality, growth, and leaf morphological acclimation of two conifer species of contrasting shade tolerances: Douglas-fir and western hemlock (Tsuga heterophylla (Raf.) Sarg.). Results after two growing seasons indicated that Douglas-fir mortality occurred mainly at relative light intensity (RLI) below 20%, while western hemlock mortality was evenly distributed along the light gradient. Height, diameter, and biomass of the planted seedlings increased with increasing light for both species but at different rates, and maximum biomass accumulation always occurred in the open. Douglas-fir allocated more resources to stem biomass than western hemlock, which accumulated more foliage biomass. Increases in specific leaf area for Douglas-fir seedlings occurred at RLI ≤ 0.4 and red/far red (R/FR) ratio ≤ 0.6, which appear to be the minimal optimum light levels for growth. Conversely, western hemlock seedlings adjusted their leaf morphology in a more regular pattern, and changes were less pronounced at low light levels. These results, along with early mortality results for Douglas-fir, suggest that the most successful way to artificially regenerate this species may be by allowing at least 20% of RLI for ensuring survival and at least 40% RLI for optimum growth. Key words: light, light quality, leaf morphology, acclimation.

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