United Slates Department of Agriculture Forest Service Agriculture Handbook 521 0^1 Diseases of Pacific Coast »> K to§4f^K 4^^. r° V '^ ^ tS-^ä Diseases of Pacific Coast Conifers Robert F. Scharpf, Technical Coordinator, Retired Project Leader, Forest Disease Research USDA Forest Service Pacific Southwest Research Station Albany, CA ,#^^^ United States Department of Agriculture flAil) Forest Service Agriculture Handbook 521 Revised June 1993 DISEASES OF PACIFIC COAST CONIFERS Robert F. Scharpf U.S. Department of Agriculture Forest Service Agriculture FHandbook No. 521 Abstract Scharpf, Robert F., tech. coord. 1993. Diseases of Pacific Coast Conifers. Agrie. FHandb. 521. Washington, DC: U.S. Department of Agriculture, Forest Service. 199 p. This handbook provides basic information needed to identify the common diseases of Pacific Coast conifers. FHosts, distribution, disease cycles, and identifying characteristics are described for more than 1 50 diseases, including cankers, diebacks, galls, rusts, needle diseases, root diseases, mistletoes, and rots. Diseases in which abiotic factors are involved are also described. For some groups of diseases, a descriptive key to field identification is included. Oxford: 44/#5—1 747 Coniferae (79) Keywords: Diagnosis, abiotic diseases, needle diseases, cankers, dieback, galls, rusts, mistletoes, root diseases, rots. Contents Preface iv Acknowledgments iv Introduction v CHAPTER 1 Abiotic Diseases 1 CHAPTER 2 Needle Diseases 33 CHAPTER 3 Cankers, Diebacks, and Galls 61 CHAPTER 4 Rusts 83 CHAPTERS Mistletoes 112 CHAPTER 6 Root Diseases 136 CHAPTER? Rots 150 Glossary 181 Index to Host Plants, With Scientific Equivalents 188 Index to Disease Causal Agents 191 For sale by the U.S. Government Printing Office Superintendent of Documents, Mail Stop: SSOP, Washington, DC 20402-9328 ISBN 0-16-041765-1 Preface This publication is a major revision of U.S. Department of Agriculture Handbook 521, first issued in 1978 and slightly revised and reissued in 1979. It has been updated to include new informa- tion that will help identify many of the diseases of conifers growing along the Pacific Coast of western North America. The revisions have been made mainly to provide the latest information on diagnosis, nomenclature, and new diseases, and to expand the coverage of important diseases of the Pacific Northwest. The basic format of this handbook remains essentially the same as the original version. The expanded coverage, more and better illustrations, and new informa- tion are designed to make this handbook a useful tool in diagnosing diseases of Pacific Coast conifers. Acknowledgments We want to thank our many colleagues who willingly contrib- uted their time and effort to the revision of this handbook. Special thanks go to those who provided photographs, critically reviewed the manuscript, and suggested improvement for use by field personnel. Dave Adams California Department of Forestry Brenda Callan Canadian Forestry Research Centre, BC Canada Tom Chase South Dakota State University Fields Cobb University of California, Berkeley Greg Filip Oregon State University Everett FHansen Oregon State University Jack Marshall California Department of Forestry Art McCain University of California at Berkeley (retired) J. R. Parmeter, Jr University of California at Berkeley (retired) Jack Sutherland Canadian Forestry Research Centre, BC Canada Tim Tidwell California Department of Forestry Francis Uecker USDA Agricultural Research Service, Beltsville, MD Personnel of the USDA Forest Service Jim Byler John Kleijunas Greg DeNitto Bill Otrosina Susan Frankel John Pronos Don Goheen Mark Schultz Frank G. FHawksworth Jane Taylor IV introduction Robert F. Scharpf and Robert V. Bega Tree diseases are a natural part of the forest ecosystem. For the most part, the native diseases occur at endemic levels and only occasionally appear as spectacular or damaging epidemic outbreaks. However, even at endemic levels, damage to western forests from some diseases can, over time, be quite serious. A few introduced foreign diseases also occur in western North America, and some cause serious injury to native species. This handbook was designed to bring under one cover the basic information needed to identify some of the common diseases of Pacific Coast conifers. Although written primarily to help identify conifer diseases of the Pacific Coast states, the handbook should be useful throughout western North America where most of these diseases also occur. Diseases of seedlings or of conifers grown in nurseries are not covered in this handbook. Other publications deal specifically with seedling diseases. The information contained in this handbook is intended to serve a comparatively broad group interested in such activities as resource management, conservation, forestry, tree farming, outdoor recreation, and growing ornamental trees. Except for a few texts written on forest pathology, most of the available literature on tree diseases is in the form of bulletins, monographs, articles, and shorter contributions issued from time to time through a variety of publication outlets. A tree disease is primarily a disturbance of the normal functions of a tree or the deterioration of its parts. Therefore, it is fundamental to recognize the parts oí the tree that are attacked by disease-produc- ing agents and the kinds of disease common to them. Also, when attempting to diagnose a particular conifer disorder, the environmen- tal conditions that allow disease-causing agents to adapt and success- fully attack must be kept in mind. The roots of a tree, for example, require conditions for infection and establishment of an organism widely different from those to be found surrounding the leaves of the same tree. An organism causing a disease of living tissues may possess a different mode of attack and environment than one that produces a heart rot in the dead tissues of the heartwood. AGENTS OF TREE DISEASE Agents of disease can readily be classified as (1 ) abiotic, non- organic, nonliving agents, such as air and soil pollutants, ice, snow, wind, frost; and (2) biotic or living organisms, such as mistletoes, bacteria, and fungi. Viruses are not included because they have not been found to cause diseases of western conifers. Climate, soils, and vegetation vary greatly along the Pacific Coast. The cool, humid conditions of the Pacific Northwest contrast with the arid conditions of southern California. Aside from host specificity and biologic competition, the important factors influenc- ing the prevalence and virulence of disease pests are environmental; they include temperature, moisture, soil condition, and human influences. The same disease may, and usually does, have different degrees of intensity depending on the locale and the conditions under which the host is growing. For example, the canker fungus Botryophaeria ribis has never been found attacking the giant red- wood in its natural habitat. However, when the tree is planted in the warmer areas of western United States, B. ribis causes severe branch flagging, top dieback, and even death. The activities of humans affect most of the diseases described in this publication and must be considered in diagnosing a disease and evaluating the damage caused. On sites where trees are growing, every effort should be made to minimize environmental changes. Logging and construction work— particularly road construction and land leveling for housing, for campgrounds, and for picnic site development—are frequently a source of injury to trees. Apart from mechanical damage to above-ground parts of trees by machinery, roots can be injured if they are severed or if they are covered with excessive amounts of soil. Overdevelopment in previously undevel- oped areas may damage trees. Trees may also be damaged in indirect ways, such as through groundwater depletion or pollution. Conversely, humans must also be protected from diseased trees in recreation sites—particularly campgrounds, picnic areas, and summer home sites. Control oí hazardous trees is of prime impor- tance in both existing and future sites. Trees that fail because of disease or other agents can destroy lives and property. This publication is organized primarily for use in field diagnosis and, except for the chapters on rusts and mistletoes, it describes symp- toms based on the part of the tree attacked. Host genus and species are used as a major separation of cankers, mistletoes, and rusts. Pertinent literature citations relating to the diseases follow each chapter, and a glossary of terms and an index of hosts and diseases are included at the end of this handbook. Scientific names that have become widely accepted since the previous edition are included where appropriate. Control recommendations are not discussed except in special instances because of the continual changes in methods and materials used for control. As the environment undergoes changes, and as tree VI values continue to increase, particularly for recreational and esthetic use, specific control recommendations will also change. DIAGNOSIS OF TREE DISEASE Diagnosis of plant diseases is the art of identifying a disease from its symptoms, signs, and patterns. The symptoms (expressions of the diseased host), signs (evidences of the cause), and patterns of occur- rence provide the clues on which the investigator bases the diagnosis. The following guide will help diagnose tree disease: 1. Determine as accurately as possible the part of the plant that is actually affected. For example, the death of only