How to identify brooms in Douglas-fir caused by dwarf mistletoe.

Abstract

Dwarf mistletoe causes obvious brooms in Douglas-fir. The brooms are the easiest means of recognizing the presence of dwarf mistletoe; however, dwarf mistletoe is not the only cause of brooming in Douglas-fir. Therefore, accurate identification of dwarf mistletoe brooms is important. If no evidence of aerial shoots can be found in the brooms, and if the brooms occur infrequently, are all relatively small, or are found only in trees where a stand has been opened, then dwarf mistletoe is probably not the cause of brooming. Dwarf mistletoe brooms generally have aerial shoots present and are found in stands where brooms of various sizes are common. Three different types of dwarf mistletoe brooms can be identified in Douglas-fir. Each may affect host trees in different ways, but all are detrimental.

Citation

Tinnin, Robert O.; Knutson, Donald M. 1985. How to identify brooms in Douglas-fir caused by dwarf mistletoe. Res. Note PNW-RN-426. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 8 p