. [Bulletins on forest pathology : from Bulletin , Washington, , 1913-1925]. Trees; Plant diseases. BULLETIN No. 360 Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief. Washington, D. C. PROFESSIONAL PAPER June 17, 1916 MISTLETOE INJURY TO CONIFERS IN THE NORTHWEST,1 By James R. Weir, Forest Pathologist, Office of Investigations in Forest Pathology. CONTENTS. Page. Introduction 1 General nature of the mistletoe injury 2 Result of infection on the branches 13 Result of infection on the trunk 20 Relation of mistletoe injury to fungous at- tack 25 General suppression
. [Bulletins on forest pathology : from Bulletin , Washington, , 1913-1925]. Trees; Plant diseases. BULLETIN No. 360 Contribution from the Bureau of Plant Industry WM. A. TAYLOR, Chief. Washington, D. C. PROFESSIONAL PAPER June 17, 1916 MISTLETOE INJURY TO CONIFERS IN THE NORTHWEST,1 By James R. Weir, Forest Pathologist, Office of Investigations in Forest Pathology. CONTENTS. Page. Introduction 1 General nature of the mistletoe injury 2 Result of infection on the branches 13 Result of infection on the trunk 20 Relation of mistletoe injury to fungous at- tack 25 General suppression and fungous attack 27 Page. Relation of mistletoe injury to insects 28 Influence of mistletoe injury on the seed pro- duction of the host 30 Host affinities in relation to silviculture 31 Suggestions for control 33 Summary 37 Literature cited 39 INTRODUCTION. It is not generally known that the injury by the mistletoes to coniferous trees in the northwestern United States is such as to assume in many regions the nature of a serious forest problem. The aim of this bulletin is to point out some of the direct and indirect results of this injury. The species of trees most subject to injury are Larix accident alls (western larch), Pinus ponderosa (western yellow pine), Pinus contorta (lodgepole pine), and Pseudotsuga taxifolia (Douglas fir). Each of these treesvis attacked by a particular species of mistletoe of the genus Razoumofskya (Arceuthobium). With a few exceptions, these species very rarely occur in nature on any other than their common hosts. In the order of the above-named hosts they are Razoumofskya laricis Piper (PI. I, fig. 1), R. campylopoda (Engelm.) Piper (PI. II, fig. 2), /?. americana (Nutt.) Kuntze (PI. I, fig. 2), and R. douglasii (En- gelm.) Kuntze (PL II, fig. 1). 1 Thanks are due Mr. E. E. Hubert for assistance in the preparation of the graphs and a number of the other illustrations used in this bulletin. 24182°—Bull. 360—16 1 1. Please note that these ima
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