10 



BULLETIN 360,, U. S. DEPARTMENT OF AGRICULTURE. 



tional Forest), the following figures were assembled by Mr. T. J. 

 Starker, covering a period of 28 days of cutting : 



Western larch 556 



Western yellow pine__ 1, 221 



Douglas fir 



Total - 2, 199 



It must not be assumed that the death of these trees resulted 

 from mistletoe. It is doubtful whether the death of even a small 



percentage of them, with 



the exception of the larch, 

 can be so referred. A more 

 conservative statement 

 would be that mistletoe had 

 a large share in their death 

 by causing spiketop, the 

 brooming of branches, and 

 the formation of burls on 

 the trunk. These are com- 

 mon forms of mistletoe in- 

 jury for all three species in 

 this region and lead up to 

 serious insect infestation, 

 of which more is said later. 

 That mistletoes are capable 

 of actually causing the 

 death of their hosts is first 

 shown by their effects on 

 young growth from three 

 to eight years old. In a 

 heavily infected but very 

 open stand of yellow pine 

 on the bench lands of the 

 Spokane River, Wash. (PI. 

 Ill, fig. 1), an attempt was 

 made to ascertain the 

 'amount of injury resulting 

 to the seedlings of an aver- 

 age sample acre, which included in its area nine semimature and 

 heavily infected trees in all stages of suppression. The acre was 

 divided into plats and all young growth counted and examined as 

 to infection and the condition of the infection. The number of 

 seedlings and small growth below 8 feet in height totaled 480, which 

 is an excellent reproduction for this region. Just a little more than 

 half of this number, or 245, were found to be infected, representing 

 every possible type of infection on stem and branch. It is not to be 

 expected that these seedlings would ever grow up to form merchant- 



FIG. 7. Douglas fir killed by mistletoe. Note the 

 total absence of normal branches. The structure 

 of the brooms is here plainly shown. Note the 

 straight trunk of the larch in the background. It 

 is uninfected by mistletoe and still retains its 

 original branches. 



