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UBC Theses and Dissertations

Intensification and infection mortality of dwarf mistletoe in two stands of western hemlock Wilford, Edward Harry


The number, height and age of western hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahl) G.N. Jones) infections were recorded in two western hemlock (Tsuga heterophylla (Raf.) Sarg.) stands (44 and 130 years old) located on similar sites on the University of British Columbia Research Forest at Maple Ridge, B.C.. The rapid decrease in numbers of infections with infection age was shown to be largely due to infection mortality. The rate of intensification of the disease expressed as "doubling time" was estimated to be 40 or more years in both stands. Also estimated was a rate of vertical spread of .15 metres per year. The results differed markedly from those of other studies in similar stands, which generally predict "doubling times" of 2 to 4 years and vertical spread rates of up to .5 metres per year.

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