Studies were made on the effects of the sweetfern rust, Cronartium comptonia, on the growth and development of jack pine. Mortality four years after inoculation of first year seedlings was 58 percent. The inoculation of two and three year old seedlings resulted in less than one percent infection. Dissection studies on the main stem of infected plantation grown trees indicated that infection had occurred before the trees were ten years old. In natural stands trees of all ages were killed by the sweetfern rust but mortality was greatest in mature and over mature stands, 42 and 52 percent, respectively. The height and diameter growth of infected trees was reduced by the fungus and the rust canker was an entrance point for wood decay fungi. Basal cankers caused by the sweetfern rust fungus averaged five feet in length on mature trees. Observations over a 6 year period indicated that the fungus had a very limited spread from host to host.
Document Type: Journal Article
Professor, University of Minnesota, St. Paul
Publication date: July 1, 1964
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