2 BULLETIN 317, U. S. DEPARTMENT OF AGEICULTUBE. 



along the Spokane River Valley, and extending to the south into 

 the Blue Mountains of Washington and Oregon the mistletoes are 

 very abundant, especially on lodgepole pine (Pinus contorta) , yellow 

 pine {Pinus ponderosa), western larch (Larix occidentalis) , and 

 Douglas fir (Pseudotsuga taxi folia). In many localities the trees 

 rapidly yield to the suppressing effects of these parasites, causing 

 an open, ragged growth of the crowns, with the production of many 

 brooms. The prevalence of a particular species of mistletoe varies 

 greatly in the same general region. To illustrate: Along the hills 

 fronting on the Pend Oreille River, Idaho, the lodgepole and yellow 

 pine stands are heavily infected. Passing up the Priest River Valley, 

 another mistletoe species appears, working considerable injury to the 

 larch, whereas the same tree, wherever it occurs along the Pend 

 Oreille River, is seldom infected. The yellow pine farther up in 

 the Priest River Valley is not seriously attacked. In the Granite 

 Creek drainage area and beyond the mountains to Sullivan Lake, in 

 the Metaline Falls region of Washington, the larch is again very 

 seriously infected, whereas this mistletoe seldom occurs on the divide 

 between these points. The western hemlock {Tsuga heterophylla) 

 in the forests of northern Idaho is practically free from mistletoe, 

 as far as the observations have been carried. In a few of the more 

 open valleys several collections of mistletoe have been made from this 

 tree. At many points in Washington and British Columbia where 

 the writer has had an opportunity to collect, the mistletoe on the 

 hemlock seems more abundant. Numerous collections of mistletoes 

 are at hand from many of the forests of southern Montana, and 

 likewise from the northern part of that State and from central Idaho. 

 A trip through Oregon, Washington, and British Columbia during 

 1913 yielded much information on the occurrence of mistletoes in 

 those localities, so that it will soon be possible, with the additional 

 data now (1915) being collected, to give a fairly detailed statement of 

 the range of these parasites in the principal forest regions of the 

 Northwest. 



In order to obtain reliable figures on the damage to forest growth 

 by these plants, special studies of a directly practical nature are now 

 being conducted in several of the most important forests of the 

 regions indicated. It is believed that the results from these studies 

 will be applicable to all the forest areas of the Northwest where 

 trees of the same species are found infected by the same mistletoe. 

 At the same time, work of an experimental nature, both in the field 

 and in the laboratory, is adding to our knowledge of these parasites. 

 This work is being continued, as having a practical bearing on the 

 mistletoe problem, and will be reported upon as time and occasion 

 permit. 



