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A study of epidemics of lodgepole pine dwarf mistletoe in Alberta Muir, John Alexander


The increase of discrete populations of dwarf mistletoe (Arceuthobium americanum Nutt.) plants or infections was studied in 20 year old stands of lodgepole pine (Pinus contorta Dougl.). Mistletoe infections were selected from infected trees in three areas 100 to 200 ft. in diameter. The age of each infection was determined by dissecting the infected host wood. It was found that the number of infections established annually had increased logarithmically during the preceding 8 to 10 years. Therefore the logarithmic rates of increase in the number of infections could be calculated to describe the past epidemic growth of each mistletoe population. The logarithmic rates (equivalent to "compound" increase of 66 to 96 per cent per year) demonstrated rapid population increase. Although the three mistletoe populations had developed in apparently different environments, the population rates of increase were not statistically different. However, for the study of ecological aspects of dwarf mistletoe epidemics this approach appears quite promising.

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