A synthesis of the literature on the biology, ecology, and management of western hemlock dwarf mistletoe.

2007 ◽  
Author(s):  
John A. Muir ◽  
Paul E. Hennon
Keyword(s):  
Western Hemlock ◽  
Dwarf Mistletoe

Field evaluation of ecological differentiation of dwarf mistletoe on shore pine and western hemlock

1976 ◽  
Vol 6 (2) ◽  
pp. 225-228 ◽  
Author(s):  
R. B. Smith ◽  
E. F. Wass
Keyword(s):  
British Columbia ◽  
Field Evaluation ◽  
Field Studies ◽  
Western Hemlock ◽  
Lake Area ◽  
Dwarf Mistletoe ◽  
Varied Composition ◽  
Coastal British Columbia ◽  
Ecological Races ◽  
Shore Pine

Hemloclc dwarf mistletoe (Arcenthobiiuntsugense (Rosend.) G. N. Jones) principally infects western hemlock (Tsugaheteropliylla (Raf.) Sarg.), but it is also damaging to shore pine (Pinuscontorta Dougl. ex Loud.) growing in coastal British Columbia. Stands of varied composition were studied in the Home Lake area of Vancouver Island to compare the levels of infection in shore pine and western hemlock. Infection of shore pine occurred whether or not infected hemlock trees were present in the stand. Observations and measurements from these field studies support indications from earlier artificial inoculation trials that two ecological races of A. tsugense exist.

Growth patterns in immature and mature western hemlock stands infected with dwarf mistletoe

1984 ◽  
Vol 14 (4) ◽  
pp. 518-522 ◽  
Author(s):  
A. J. Thomson ◽  
R. B. Smith ◽  
R. I. Alfaro
Keyword(s):  
Confidence Intervals ◽  
Growth Curves ◽  
Early Growth ◽  
Growth Patterns ◽  
Western Hemlock ◽  
Stem Analysis ◽  
Dwarf Mistletoe ◽  
Infected Tree ◽  
Volume Increment ◽  
Growth Loss

Growth patterns of western hemlock, Tsugaheterophylla (Raf.) Sarg. infected with dwarf mistletoe, Arceuthobiumtsugense (Rosendahl) G. N. Jones, were studied by stem analysis. The volume increment versus age relationships of average trees were used to project growth and evaluate volume losses. Based on a particular assumption of growth loss ratios between infection classes, volume losses in moderately and severely infected trees by the age of 80 years were conservatively estimated at 15 and 25%, respectively, with respect to comparable healthy trees. As these estimates were based on projection of growth curves of average trees, confidence intervals were not calculated. Healthy trees selected from a different part of the stand generally exhibited patterns of establishment and early growth which differed from the infected trees to an extent which invalidated their use as controls for infected tree growth. Moderately infected trees were more comparable to severely infected trees from the same part of the stand. The variety of growth patterns within stands is discussed in relation to the use of the stand as a sampling unit.

HEMLOCK AND LARCH DWARF MISTLETOE SEED DISPERSAL

1966 ◽  
Vol 42 (4) ◽  
pp. 395-401 ◽  
Author(s):  
Richard B. Smith
Keyword(s):  
Seed Dispersal ◽  
Western Hemlock ◽  
Dwarf Mistletoe ◽  
Western Larch ◽  
Potential Sources ◽  
Tree Seeds ◽  
Larch Tree

During 1964-65, approximately 49,050 hemlock dwarf mistletoe seeds were dispersed from a severely infected 35-ft. western hemlock tree, and 3,750 larch mistletoe seeds were dispersed from a lightly infected 63-ft. western larch tree. Seeds were trapped over an area 5,800 ft.2 in extent around the hemlock, and over an area of 2,200 ft.2 around the larch.The peak of larch mistletoe seed dissemination was about 1 month earlier than for hemlock. Seed counts for both years and both mistletoes were highest in the southwest and least in the northeast quadrants of the trapping areas.It was firmly established that small trees, even if lightly infected, are a serious potential sources of dwarf mistletoe seed; they must be removed if satisfactory dwarf mistletoe control is to be achieved.

Dwarf mistletoe seed capsule orientation and seed discharge in western hemlock

1979 ◽  
Vol 57 (17) ◽  
pp. 1841-1844 ◽  
Author(s):  
A. J. Thomson
Keyword(s):  
Western Hemlock ◽  
Discharge Pattern ◽  
Dwarf Mistletoe ◽  
Vertical Orientation ◽  
Growth Angle

The seed discharge of Arceuthobium tsugense is closely related to the orientation of the seed capsule. The distribution of capsule orientations may therefore be used as a guide to the discharge pattern. With plants on the periphery of the crown, the azimuth orientation of the capsules directs seeds outward from the crown, whereas plants within the crown have an inward direction of azimuth capsule orientations. The distribution of vertical orientation angles is related to the growth angle of the branch bearing the infection. Infections near the crown periphery would appear to be more related to spread of infections, whereas those within the crown are related to intensification.

Pentaketide metabolites from Potebniamycesgallicola n. sp.

1983 ◽  
Vol 61 (10) ◽  
pp. 2285-2286 ◽  
Author(s):  
Camille A. Boulet ◽  
Gerald A. Poulton
Keyword(s):  
Western Hemlock ◽  
Malt Extract ◽  
Dwarf Mistletoe ◽  
Related Compounds

The fungus Potebniamycesgallicola n. sp. has been isolated from cankered swellings of western hemlock (Tsugaheterophylla (Raf.) Sarg.) produced by the dwarf mistletoe (Arceuthobiumtsugense (Rosendahl) G. N. Jones), and has been implicated in the induction of disease in the infected trees. P. gallicola was cultured on malt extract, and four isoprenylated pentaketide metabolites were isolated by extraction; these were identified as the known compounds fuscin 1 and dihydrofuscin 2, and two related compounds secofuscin 3 and dihydrosecofuscin 4, not previously reported in nature.

Development of dwarf mistletoe in western hemlock regeneration in southeast Alaska

1982 ◽  
Vol 12 (3) ◽  
pp. 482-488 ◽  
Author(s):  
Charles G. Shaw III
Keyword(s):  
British Columbia ◽  
Disease Control ◽  
Control Strategies ◽  
Severe Infection ◽  
Host Tissue ◽  
Western Hemlock ◽  
Dwarf Mistletoe ◽  
Local Conditions ◽  
Southeast Alaska ◽  
Understory Trees

Western hemlock (Tsugaheterophylla (Raf.) Sarg.) regenerated within 9.14 m of old-growth hemlock severely infected with dwarf mistletoe, Arceuthobiumtsugense ((Rosendahl) G.N. Jones), and left standing on cutover sites in southeast Alaska were felled and examined for infection. The percentage of understory trees infected among the 3429 examined averaged 9, 7, 5, and 17, respectively, in 17-, 19-, 35-, and 43-year-old stands. Ninety-two percent of all infections in the 17-, 19-, and 35-year-old stands were alive, but only 51% were alive in the 43-year-old stand. In all stands few trees had more than two live infections and few had any infections in their middle or upper crown. In all stands, advanced regeneration was more frequently infected and accounted for a significantly greater proportion of crop trees than new reproduction. A significantly higher proportion of hemlock crop trees were infected than non crop trees, but the number of infections on crop trees was consistently low. Most infections were established on host tissue 5 years or younger, but tissue up to 13 years old was infected. At a comparable age, young stands in Alaska appear to be less severely affected by A. tsugense than similar stands in Washington, Oregon, and British Columbia. Disease control strategies, developed for stands experiencing more severe infection intensities than those now known to prevail in southeast Alaska, will require modification to meet local conditions.

Measurement and simulation of dwarf mistletoe infection of second-growth western hemlock on southern Vancouver Island

1982 ◽  
Vol 12 (2) ◽  
pp. 280-291 ◽  
Author(s):  
W. J. Bloomberg ◽  
R. B. Smith
Keyword(s):  
Growth Rate ◽  
Vertical Distribution ◽  
Stand Density ◽  
Tree Height ◽  
Vancouver Island ◽  
Western Hemlock ◽  
Dwarf Mistletoe ◽  
Infection Level ◽  
Infection Age ◽  
Second Growth

Infection of western hemlock (Tsugaheterophylla (Raf.) Sarg.) residual overstory and second-growth understory by hemlock dwarf mistletoe (Arceuthobiumtsugense (Rosendahl) G.N. Jones) was analyzed in seven plots on southern Vancouver Island. The number of infections in residual trees ranged from 373 to 4058 and in second-growth trees from 3 to 455. The number in second-growth trees was significantly correlated positively with dbh and tree height and inversely with height/dbh ratio. The percentage of crown length infected varied significantly among plots and was significantly correlated with the number of infections. Vertical distribution of infections in tree crowns did not conform to test distributions; distribution by infection age approximated the Poisson. The range in infection age varied according to height in green crown and length of green crown infected. Mortality of infections varied significantly among plots and was greatest in lower slope sites and least in a drier upper slope site. Proportion of dead infections was a function of height in crown and total length of green crown infected. Data suggest that infection level in second-growth trees was proportional to the number of residuals and was inversely related to percent nonhost species, stand density, and growth rate. The number of infections predicted by a simulation model averaged 107% of the number recorded in residual trees and 128% in second-growth trees. Curves of predicted vertical distribution of infections in crowns were of the same shape as those recorded in plot sample trees. The predicted average age-class distribution of infections approximated Poisson distribution within the same probability range as recorded in plot sample trees. The predicted average dbh of residual and second-growth trees were 90 and 97%, respectively, of the recorded values; predicted average heights were 115 and 101%, respectively, of recorded values. Infection predicted by the model over a range of hypothetical stand, site, and infection conditions was used to elucidate major epidemiological factors that might bear on silvieultural control. Results confirmed the observed effects of number of residuals, stand composition, growth rate, and stand density on infections.

A model of spread and intensification of dwarf mistletoe infection in young western hemlock stands

1980 ◽  
Vol 10 (1) ◽  
pp. 42-52 ◽  
Author(s):  
W. J. Bloomberg ◽  
R. B. Smith ◽  
A. Van Der Wereld
Keyword(s):  
Seed Production ◽  
Computer Model ◽  
Tree Species ◽  
Stocking Density ◽  
Western Hemlock ◽  
Tree Crown ◽  
Field Plot ◽  
Dwarf Mistletoe ◽  
Source Tree ◽  
Residual Tree

The following relationships were quantified in a mathematical computer model to predict spread and intensification of dwarf mistletoe (Arceuthobiumtsugense (Rosendahl) G. N. Jones) infection, originating from residual trees, in regeneration of western hemlock (Tsugaheterophylla (Raf.) Sarg.): distribution of dwarf mistletoe infections in residual source trees, dwarf mistletoe seed production, escape from crown and dispersal, interception of seeds by neighboring trees, distribution of seeds within crowns, development of dwarf mistletoe infections, mortality of plants, and tree crown growth. The model included options for thinning or sanitation by removal of infected residual or regeneration trees. Predictions by the model for a 10-year period did not differ significantly (p = 0.05) from results of a field plot with respect to average number of infections per tree, percentage of infections at 1-m distances from the residual tree, and percentage of infections in each quadrant centered on residual source tree. Predictions of the effects of stocking density and sanitation or thinning on infection agreed with results obtained from experiments with other tree species.

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