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Toreign Diseases of Forest Trees of the World U.S. D-T. pf,,„,ç^^,^^ AGRICULTURE HANDBOOK NO. 197 U.S. DEPARTMENT OF AGRICULTURE Foreign Diseases of Forest Trees of the World An Annotated List by Parley Spaulding, formerly forest pathologis Northeastern Forest Experiment Station Forest Service Agriculture Handbook No. 197 August 1961 U.S. DEPAftTÄffiNT OF AGRICULTURE ACKNOWLEDGMENTS Two publications have been indispensable to the author in prepar- ing this handbook. John A. Stevenson's "Foreign Plant Diseases" (U.S. Dept. Agr. unnumbered publication, 198 pp., 1926) has served as a reliable guide. Information on the occurrence of tree diseases in the United States has been obtained from the "Index of Plant Dis- eases in the United States" by Freeman Weiss and Muriel J. O'Brien (U.S. Dept. Agr. Plant Dis. Survey Spec. Pub. 1, Parts I-V, 1263 pp., 1950-53). The author wishes to express liis appreciation to Dean George A. Garratt for providing free access to the library of the School of Forestry, Yale University. The Latin names and authorities for the trees were verified by Elbert L. Little, Jr., who also checked the common names and, where possible, supplied additional ones. His invaluable assistance is grate- fully acknowledged. To Bertha Mohr special thanks are due for her assistance, enabling the author to complete a task so arduous that no one else has attempted it. For sale by the Superintendent of Documents, iTs. Government Printing Ofläee- Washington 25, D.C. — Price $1.00 *^ CONTENTS Page Introduction 1 The diseases 2 Viruses 3 Bacteria 7 Fungi 13 Host index of the diseases 279 Foreign diseases potentially most dangerous to North American forests__ 357 m Foreign Diseases of Forest Trees of the World INTRODUCTION Diseases of forest trees may be denned briefly as abnormal physi- ology caused by four types of factors, singly or in combination: (1) Nonliving, usually referred to as nonparasitic or site factor; (2) ani- mals, including insects and nematodes; (3) plants; and (4) viruses. This handbook deals only with diseases due to plants and viruses. Although diseases caused by nonliving factors are not included, it must be clearly understood that low vigor of trees, not only resulting from unsuitable site but also induced by defoliation, can be disastrous because they increase susceptibility to severe attacks by semipathogens. This Is particularly true of planted and exotic trees. Diseases of slight importance on naturally regenerated trees in their native range often are serious to trees planted on unsuitable sites and may be destructive to exotics. Conversely, obligate parasites tend to attack the most vigorous host trees and leave subnormal ones unscathed. Thus, sub- normal vigor may decrease danger from obligate pathogens, but it may increase danger from semiparasites. Growth vigor of exotics is de- sirable, but no guarantee that an exotic will not be attacked if planted extensively. The pests that cause tree diseases do not confine their activities within political boundaries. Many diseases have been introduced into North America ^ from abroad, for example, white pine blister rust, larch canker, and Ceratocystis {Ceratostomella) elm disease from Europe ; and the chestnut bark disease from China. These introduc- tions into North America and similar ones into many other countries make it essential to have readily available more information on forest tree diseases of all countries. To this end a survey was made of published reports on the infectious forest tree diseases of the world. The causal agents included are viruses, bacteria, and fungi. Algae and lichens are not included be- cause they cause relatively few and imimportant diseases. The mistle- toes are not included as they are considered in detail, with over 2,100 references to ih^ world literature on them, in Technical Bulletin 1242 by Lake S. Gill and Frank G. Hawksworth, entitled '^The Mistletoes; A Literature Review." Robert Hartig, who is rightly called "the father of forest pathol- ogy," began his investigations about 1870, and except for a few earlier publications that have been reviewed, this survey covers the period from 1870 to about 1955. 'The term "North America" as used in this publication includes the areas of Alaska, Canada, and the United States. 2 AGRICULTURE HANDBOOK NO. 197, U.S. DEPT. OF AGRICULTURE The publications examined include numerous forestry and arbori- cultural journals, abstracting journals, reports by forestry organiza- tions, pathological and mycological papers, and some comprehensive annotated lists of fungi of foreign countries. The results of this survey are being pubhshed m three parts, of which two have already been issued, namely, "Diseases of North American Forest Trees Planted Abroad," U.S. Dept. Agr., Agr. Handb. 100, 144 pp., 1956 ; and "Diseases of Foreign Forest Trees Growing in the United States," U.S. Dept. Agr., Agr. Handb. 139, 118 pp., 1958. ^. , . ^ . This third, and final handbook in the series lists the infectious foreign forest tree diseases of the world, with indication of the damage caused and the potential danger to other regions outside the known range of each pathogen. The distribution given is the reported distribution of the pathogen on all hosts, and includes saprophytic as well as parasitic occurrences. "iVhere known, the occurrence of foreign diseases of forest trees in North America is given, to show the entire reported range of such pathogens. The term "forest trees" is used for trees growing in planted or naturally reproduced forest stands. Shrubs and woody vines are not usually included. A tree that exists in extensive wild stands within its native range and is grown in planted stands outside its native range, but not in fruit orchards in the common meaning of that term, is considered a forest tree. The references accumulated in this entire survey, although incom- plete, number well over 3,000. These are strongly directed toward the forestry viewpoint. They are available for reference on index cards filed at the Forest Disease Laboratory, Northeastern Forest Experiment Station, New Haven, Conn. THE DISEASES This publication lists the parasitic (pathogenic) diseases of forest trees in foreign countries." These diseases are separated into three groups according to the type of causal agent : Viruses, listed by common names. Bacteria, listed by Latin names. Fungi, listed by Latin names. The scientific name of each pathogen includes the author of the name, followed by (x), (xx), or (xxx) indicating the class of para- sitism of that pathogen. It is believed important to point out this character as foretelling possible action of the pathogens when they arrive in a region not previously infected. Accordingly, three classes of parasitism have been set up. The first (x) class includes semipathogens that normally live sapro- phytically but cause disease occasionally under suboptimum conditions for the host tree, or under conditions especially favoring increase in the vigor of the pathogen. The second (xx) class includes wound parasites that can attack trees only through wounds that expose inner living tissues to easy attack. ' The term "foreign countries" includes aU land areas not in Alaska. Canada, and continental United States. FOREIGN DISEASES OF FOREST TREES OF THE WORLD 3 Nearly all decays of living trees and a considerable number of other tree diseases are of this type. Many Tvoimd pathogens can live saprophytically for years. Published reports of wound parasitism are but a small sample of all occurrences, as infection of wounds is very erratic and easily overlooked in early stages of decay. Numerous instances are given in the text where only one or two hosts are listed as being parasitized ; these are merely isolated published cases out of hundreds that have escaped mention in print. Class three (xxx) pathogens are obligate parasites, able to attack healthy, uninjured trees. In fact, many obligate parasites, such as the white pine blister rust fungus, attack the most vigorous and thrifty trees, whereas suppressed individuals escape. Each disease is annotated with the available data on life history, severity, and general distribution of the pathogen. By far the greater number of tree diseases are caused by fungi. Fungi are living organisms and exhibit individuality. iMoreover, of late years many fungus species have been found to have numerous races, often varying in pathogenicity. Parasites that are widely and generally distributed in one region may have especially aggressive races not yet present in other regions. Intensive investigation has shown that black stem rust of wheat has hundreds of races varying in pathogenicity and host specificity, and is constantly developing new races. Somewhat similar action is to be expected of some tree-inhabiting fungi, such as Armillaria meJJea^^ with its worldwide range and numerous recognized varieties, indicating ability to vary distinctly. Although this fungus is common in nearly all forests, its introduction from another region on nursery trees or wood, or in soil from overseas, might materially increase the root-rot problem for some of the tree species in other continents. The same fact is undoubtedly true, although probably to a lesser extent, for other forest pathogens. A conmion name for a disease is given, wherever known. Synonyms of Latin tree and fungus names are omitted, the name given being that believed to be technically correct according to the International Code of Botanical Nomenclature and generally accepted or most commonly used. Agriculture Handbook No. 100, issued in 1956, listed records of diseases of North American forest trees growing in other countries ; but a number of such records not included in that publication have been found. They are listed here without individual comment on their native range. Viruses Virus diseases have been known the world over for many years, but their causes have become known only during the past few decades. Vims diseases of economic crops have received the most study. Some forest tree viruses are well known and there are, undoubtedly, many undiscovered viruses in forests of the world that will be found when more intensive studies can be made.

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