Douglas-fir needle blight
Damage, symptoms and biology
Repeated severe infection almost completely defoliates trees, leaving only the current year's needles. The impact of the disease therefore is greatest on small trees because of their smaller total number of needles; large trees usually undergo only light defoliation and sustain little damage. Christmas tree plantations can be severely damaged.
Douglas-fir needle blight is caused by a number of species and subspecies of the genus Rhabdocline. The most common in British Columbia is R. pseudotsugae described here, and R. weirii (Parker & Reid). The symptoms caused by these organisms are similar, however, so precise identification is seldom important. Epidemic infection years occur in cycles and depend on climatic conditions during the infection period. Occasionally individual trees show marked resistance to the disease.
Canadian Forest Service Publications
Information on host(s)
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