File:Bulletins on forest pathology - from Bulletin U.S.D.A., Washington, D.C., 1913-1925 (1913) (20504894155).jpg

Title: (Bulletins on forest pathology : from Bulletin U.S.D.A., Washington, D.C., 1913-1925)
Identifier: bulletinsonfores00unit (find matches)
Year: 1913 (1910s)
Authors: United States. Dept. of Agriculture
Subjects: Trees; Plant diseases
Publisher: (Washington : U. S. Dept. of Agriculture)
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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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 422 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-
Text Appearing After Image:
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.

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