MISTLETOE INJURY TO CONIFERS. 



17 



yellow pine and Douglas fir (fig. 15) and is the rule for larch. The 

 stunting effect of these brooms on the trees as a whole was in one 

 instance very interestingly shown by the fact that a middle-aged 

 Douglas fir increased the radial dimensions of its annual rings after 

 the removal by the wind of an immense broom located midway on 

 the trunk. The weight of the brooms on some conifers is very often 

 greatly increased by the accumulation of dead needles, lichens, etc. 

 (fig. 11). When loaded with snow or saturated with moisture the 

 brooms are more 

 easily broken off by 

 high winds. The 

 ground around the 

 base of heavily in- 

 fected larches is very 

 frequently littered 

 with brooms broken 

 off in this manner, 

 often insuring the 

 death of the tree in 

 case of ground fires. 

 During the early 

 part of October, 

 1914, an unusually 

 heavy fall of soft 

 snow occurred locally 

 over a small area 

 around Missoula, 

 Mont. The snow ac- 

 cumulated in such 

 quantities on the mis- 

 tletoe brooms of the 

 larches and Douglas 

 firs throughout the 



area that the ground around the more heavily infected trees was piled 

 high with fallen brooms. 



The foliage of old and mature mistletoe brooms is usually not 

 as long lived as that of normal branches of uninfected trees. This 

 is not true in the case of young well-nourished brooms. It has 

 been observed to any extent only in old brooms which have begun 

 to tax the food supply of the tree or the branch on which they are 

 located. In the course of one year it was determined that 655 more 

 needles fell from a small but mature broom on a Douglas fir than 

 from a normal branch of a neighboring uninfected tree of the same 

 species. The number of needles falling from the broom totaled 

 24182 Bull. 36016 3 



FIG. 15. Fallen brooms split from the trunk of a Douglas 

 fir and piled about the base of the tree a serious fire 

 menace. 



