Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. ‘ i ey 4 D the ne M i \ * = i { s ' ‘ W _ " j ‘ ~*~ ie = te ' ‘ 4 7 > a j * cd ‘ + = . ‘ ‘ j NTERNATIONALLY _ DANGEROUS FOREST TREE DISEASES MISCELLANEOUS PUBLICATION NO. 939 TOREST SERVICE U.S. DEPARTMENT OF AGRICULTURE a ee Internationally Dangerous Forest Tree Diseases By Working Group on International Cooperation in Forest Disease Research, Section 24, Forest Protection, International Union of Forestry Research Organizations Supplement to Section 24-14, Proceedings of the 13th Congress, International Union of Forestry Research Organizations, Vienna 1961 Miscellaneous Publication No. 939 September 1963 U.S. Department of Agriculture Forest Service MEMBERS OF WORKING GROUP ON INTERNATIONAL COOPERATION IN FOREST DISEASE RESEARCH ASIA B. K. Baxsut, Forest Research Institute, Dehra Dun, India R. Imazext, Forest Experiment Station, Meguro, Tokyo, Japan EKUROPE A. Brracut, Institute of Forest Pathology, Florence, Italy M. M. Krstic, Forest Experiment Station, Belgrade, Yugoslavia K. Lonwae, Hochschule fiir Bodenkultur, Vienna, Austria T.R. Peace, Forest Research Station, Farnham, Surrey, England F. Rotit-Hansen, Forest Research Institute, Vollebekk, Norway H. van VuoTeN, Forest Experiment Station, Wageningen, Nether- lands NORTH AMERICA V. J. Norpin, Department of Forestry, Ottawa, Ontario, Canada J.S. Boycr, Yale University, New Haven, Connecticut, U.S.A. A.J. Riker, University of Wisconsin, Madison, Wisconsin, U.S.A. J. R. Hanssproucu, Department of Agriculture, Washington, D.C., UES AL For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 - Price 40 cents FOREWORD One of the hazards of international trade is the possible move- ment of dangerous insects and pathogens accompanying the exchange of agricultural and forest products. To illustrate, of the major plant pests and diseases that cause losses in excess of a billion dollars an- nually and necessitate costly control programs in the United States, over half were introduced from other continents. Included among the major introduced diseases are three that have taken and continue to take a tremendous toll from North American forests: chestnut blight, white pine blister rust, and Dutch elm disease. All practical precautions should be taken to prevent the introduction of additional dangerous forest pathogens and every effort made to provide ad- vance information on eradication or control procedures for those that may be accidentally introduced. The accomplishment of these objectives is dependent on interna- tional cooperation to recognize and characterize those forest tree pathogens in each continent considered to be potentially dangerous if introduced to other continents and to promote measures to restrict their spread. To that end, the Forest Service of the United States Department of Agriculture has participated in the work of the In- ternational Union of Forestry Research Organizations, particularly in the activities of the Working Group on International Cooperation in Forest Disease Research. The report of this Working Group to the 13th Congress of the parent organization in Vienna in 1961 is a significant contribution to improved forest disease prevention and control in all lands. The Forest Service, therefore, welcomes the op- portunity to publish it for worldwide distribution and use. This publication is truly the result of cooperative effort. It as- sembles under one cover the reports of 37 scientists from 14 countries in Asia, Europe, and North America. It includes descriptions of 57 forest pathogens in the Northern Hemisphere considered to be potentially most damaging to forest production in other continents, with recommendations for special precautions to restrict their inter- continental spread. These diseases occur on 87 genera of forest trees, of which 50 genera are important in the United States. The text of the separate reports is with few exceptions as sub- mitted by the various authors. No attempt has been made to adopt a uniform system of nomenclature for pathogens and hosts. This publication is a Supplement to Section 24-14 of the Pro- ceedings, 13th Congress, International Union of Forestry Research Organizations, Vienna, 1961. V. L. Harper che Deputy Chief, Forest Service U.S. Department of Agriculture (Vice President, IUFRO) m1 CONTENTS Ewerress Tepoert of the working group:--___---2_.._-7 2-22 is. Organization and objectives__________- J. R. Hansbrough Ber amnplisiinenus: SiSiae ees eae tse See ee Be ee ee ee [JLRS (Oe an OR iis Reals ill a Sea Rokuya Imazeki Siagiieeere soe it Ae SS FE B. K. Bakshi Reisist aie. ote ee ee re A. H. Khan Pann pines. 2a7.e eee. fees Sa See Tiburcio 8S. Serevo Rarhinde = 2a Bee ee Seat BSS H. G. Hundley pecomplushments: Hurope_=..2--.222..-2202.- 2-222 --2 2-2 =.-- EU Oe) Ee ed Se ae M. M. Krstic WW echosionakia. 2-520) 2 Ls tse I. A. Kalandra Renieiritalme me tee. ye Mosse T. R. Peace United States Department of Agri- TL EAU ee a ha lp J. R. Hansbrough Mimited suates. 2 Se Mis 2 se A. J. Riker S0TEiL Ls ee eet jot Ee ee J. R. Hansbrough Selected dangerous forest diseases in Asia, Europe, and North America: eer a Ag ener ee mee 2 es Sot eRe ae ee Sek Dangerous forest diseases in Japan_________ R. Imazeki and K. Ito Matches broom of paulowmia >. 25222522 Psxetenial plicht.of CheSstnUb.. <7. MeEcticncasit@nt ales eee nn ee ee ee ee eee SHootspneitrOriarch: 2-22.) iL ite “See ee Per MEVENOSe IOIMACACTA fe 8) oe ee le ek oc eatmeMOhenMOINpO Dai snes. on I A ee ee Be ee Re PeLOOn tO ee een ey ee ee ee Meedle blight and canker of eryptomeria_— ______ 9 __-_____-_-__2- Percucmoliemi tor pine 221s s ol eye. Pvh sos ee SI RaGucmsensclonmehestmiit <2! Bou. ee kek oe eee peek eee eee o (SEL AIS er TT eS ee ee eee ee en ee Mecdlewust of o-needle pine. .2.. 2. a ee ee eee eee PIM SOU OG LUNE 2 8 os ee kek Picedia ileltt Or red woods: 22.2 sees 8 ey eek Dangerous forest diseases in India_________ B. K. Bakshi pmeceeisease On SAMMal eo ek ee te eae aaayitenes: broom... ee Oe ee Wirmaiie woster nists see: oe. AN a SL See Ue Spee Shee = = as eked ee a ed Are oth te rc be ee (LEE IGS TS ee Se ee Se a ir ee ee ae See eee cee “LS VST) “OT ek oe il ag dl ee ene pee ein) Chaptae Meet eines Retire eer S5.§ 3 ee eke Lolbpey Inemive Ge: ga Seer aes Ya, Se eee eee eee ees SL ESRI ETRE Sortprice Sel Dangerous forest diseases in Yugoslavia____ M. M. Krstic Lerma Hight oF poplars#2)220_ 22. Lie. 2 ee folie Se reerrinnioimormland anak phy toen «Of op ee 8 Ls em ose aeietiniecanker Of ashe so. 420 ee ee ke ieee Dangerous forest diseases in Austria______- Kurt Lohwag AUPHPDOVEOT CECA eae et gM Li A peg i ec Seba keciainincdivra irl ae ee. Lo oees br a Ee a ULANEC Geren ed en ge Sle he oe eee Do ee PerlarchoL HOrSe ChEStMUt 0 20-2 eer vee Rennes oe ee ee eT ee Comments on snow blight____________ Erik Bj6rkman VI CONTENTS Page Dangerous forest: diseases in western Europe _2. 2224-22222 ee 73 Scots pine blister rust___.___._.__..._- F. Roll-Hansen Larch canker and dieback= 2) 232. 232 H. Robak Hypodermella needle cast of pine__-_-_-_-_ H. Robak Pine ttwist PUSS. oko yee ee ieee J. Gremmen Top canker of spruce and pine__-_-__-_-_- E. BjOrkman Dangerous forest diseases in North) Americal-22 4. 2 eee 82 Introduiction 26. eee ee 2 ah So he Se 82 Brooming disease of black locust_-____-_ ad. Grant Phloem necrosis of elm: ae aes R. U. Swingle Atropellis canker of pine___--_____-__- J. C. Hopkins Persimmon: wilt 2222 ee ee eee G. H. Hepting CG Fil ea bt ep es = aL eee Sivegr yor PE WER C. E. Seliskar Canker stain of plane trees__________- Curtis May Clitocy be root rote) 22 ee en eee W. A. Campbell Spruce: broant rust. se es ae eee R. 8. Peterson Comandra’ blister must=-2--2 3.2. 23" " J. L. Mielke Southern fusiform rusts2 (2-22 22 os A. F. Verrall astern pall mists. 52-4522 2 oe eee J. E. Nighswander Ponderosa pine needle cast__________-- T. W. Childs Gray blicht of hard pines2- === = 2a ees G. D. Darker Hypoxylon canker of aspen__________- J. R. Hansbrough Cedar leaf blight) = 2260s) Tee eee soe J. S. Boyce Western gall rust (woodgate rust)_____ W. G. Ziller SealacuiOrm FUSt 2-6 ee ee ee W. G. Ziller Cedar PliemG . 2s) oe ee ae ae eee G. W. Peterson Phymatotrichum root rote. 5252s Ernest Wright Poria root rot of Douglas-fir _____-__-__- G. W. Wallis Par tip: Diigh tees. eet Tad ae M. E. Fowler Brown-spot needle blight_---_--------- A. F. Verrall Septoria canker of poplars].-~ 32-22 2- J. E. Bier Strumelia canker of oaks- 2" 72 a J. R. Hansborough Dwarfmistletoes of conifers__________- Job Kuijt Principles of forest disease control -_-_------- J. S. Boyce Lessening the threat of internationally danger- ous tree diseases? 2257s Se ae ese oan ee oe A. J. Riker Discussion and. recommendations. = 2 eee 122 DO ee re aN PROGRESS REPORT: WORKING GROUP ON INTERNATIONAL COOPERATION IN FOREST DISEASE RESEARCH Organization and Objectives J. R. HansproucH, CHAIRMAN Director, Dwision of Forest Disease Research, Forest Service, US. Department of Agriculture, Washington 25, D.C., U.S.A. One of the topics considered at the 12th IUFRO Congress, Oxford, 1956, was the problem of the intercontinental spread of forest tree diseases and the need for international cooperation to lessen their threat and to reduce losses from those already introduced abroad. Ex- amples were cited of the catastrophic losses in the past from introduced forest pathogens such as E'ndothia parasitica (Murr.) P. J. & H. W. And., Cronartium ribicola J. C. Fisch., and Ceratocystis ulmi (Buis.) Moreau, respectively the causes of chestnut blight, white pine blister rust, and the wilt disease of elm. There was complete agreement on the need for increased international cooperation in forest disease research. Four measures were recommended for immediate attention: (1) Literature reviews of the forest diseases of all continents, (2) studies by pathologists of one continent of the forest diseases of other conti- nents, (3) test plantings of all species in a genus to determine their susceptibility to a specific disease (e.g., oak species susceptibility to oak wilt), and (4) test plantings of the most important tree species of each continent on other continents to determine their susceptibility to native diseases. In 1957 a working group in Section 24 was organized to carry out these recommendations. Membership included representatives from Asia (India and Japan), Europe (Austria, England, Italy, Nether- lands, Norway, and Yugoslavia), and North America (Canada and the United States). The objectives of this working group were to secure more information on the forest tree diseases of all continents, to evalu- ate their potential impact on important forest tree species of other continents, and to develop and improve methods of preventing the spread of diseases from one continent to another. It was agreed that initially the working group would concentrate its activities primarily on the diseases of three genera—Pdnus, Populus, and @uercus—in the North Temperate Zone. Each member would attempt to stimulate special studies of the diseases of these genera 1n his country and adjacent countries and see that the results were pub- lished. In addition, special efforts would be made by all to insure dis- tribution of new information on important forest diseases to patholo- gists and foresters in other countries and continents. -_ We meet here today to review our accomplishments as individuals and as a group. We have carried on research or stimulated others to do so on forest disease problems in our respective areas. We have 1 a OO as ee 2 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 released and distributed publications. We have made some progress in establishing plantations of exotic forest trees to determine their susceptibility to local diseases. Above all, but much more difficult to appraise and document, we have made an excellent start in creating a public awareness of the magnitude of forest disease losses and in promoting serious consideration of methods of reducing them. One evidence of the effectiveness of our work to date is this sym- posium in which we will review selected dangerous forest diseases in the continents of the North Temperate Zone. If the information thereby made available is used to deter or prevent the international spread of even one of the pathogens discussed, this Congress will be a success and our working group will have justified its establishment. Our efforts and our progress so far are but the first step toward our ultimate objective of lessening forest disease losses in all continents. We will discuss the possibilities of broadening our group activities to stimulate forest disease research, education, and action programs throughout the world. One way would be to organize another symposium in the near future with worldwide coverage of selected pathogens considered to be most dangerous if introduced to other con- tinents. Other ways would be (1) to encourage preparation and wide distribution of reports listing under each genus of important forest trees the name, diagnostic characteristics, and distribution of dan- gerous pathogens; (2) to recommend more effective quarantine proce- dures; and (3) to organize a corps of specialists in each continent responsible for promoting forest disease research, prevention, and control activities. As chairman of your working group, I want to express my sincere appreciation to each member for your hearty cooperation in our activities, especially for the way that you have participated in the preparations for this Congress. Also, I wish to thank our section leader, Dr. Biraghi, and our president, Mr. Macdonald, for their invaluable assistance in scheduling our meetings and otherwise con- tributing to our objectives. With the continued enthusiastic support of all concerned, I am sure that our future contributions to the advancement of forest disease control programs can be increasingly significant. ACCOMPLISHMENTS: ASIA Japan RokuyA IMAZEKI Director, Division of Forest Protection, Government Forest Experiment Station, Meguro, Tokyo, Japan Many kinds of exotic trees, introduced from continental Asia, Eu- rope, North America, and other countries, have been planted in Japan during the past 70 or more years. Some of them were cultivated in arboreta for merely botanical purposes, but others were planted in various parts of the country on a larger scale for silvicultural exper- iments. These experimental plantations, however, were prompted simply for experiment’s sake or sometimes for curiosity and, there- fore, no systematized investigations have been carried out. After the war, the loss of forests in overseas colonies, the drain of resources, and the greatly increased timber demand led to extreme disorganization in timber supply and demand, and consequently the policy of increasing timber production became the urgent problem to be solved in Japanese forestry. Among ways of solving this prob- lem, the introduction of exotic trees is considered promising and an organized survey of existing plantations of exotic trees is considered essential. At that time, the proposal on the cooperative international invest1- gation of the diseases of exotic trees was presented to Prof. N. Taka- hasi, the former representative of the Working Group of Eastern Asia, by Dr. A. Biraghi and Dr. J. R. Hansbrough. Though Prof. Takahashi did not specialize in forest pathology, he had a profound comprehension of the importance of the forest disease and pest problem as applying to future forestry in Japan. He visited the Government Forest Experiment Station in Toyko in order to deliberate this proposal with me and Dr. K. Ito, the chief of the Section of Forest Pathology in our Division. Needless to say, there could be no two opinions as to the advisability and urgency of the matter, and we decided willingly to accept this proposal, and to organize the Working Group of Eastern Asia. We recommended Prof. Takahashi as the representative of the Working Group for the time being, and decided that the other two should actively push forward the work. The first project undertaken by the Working Group was to carry out a fundamental survey of the diseases and pests of exotic trees which had been introduced into Japan to that time. In order to accomplish this as quickly as possible, it was very neces- sary to ask for the help of plant pathologists and entomologists in the agricultural field. Accordingly, we consulted with Prof. N. Hiratsuka and others, who are mentioned below, and succeeded in organizing a joint research group. The joint research was financially supported by the Forestry Agency and started in the spring of 1959, working to a 3-year program. The members of this group are as follows: 3 4 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Person in charge.—Prof. N. Hiratsuka, Tokyo University of Edu- cation. Pathologists.—Prof. N. Hiratsuka, ex-Prof. Senji Kamei, Hok- kaido University; Prof. Nobukiyo Takahashi, Tokyo University; Asst. Prof. Katsuya Nakamura, Tokyo University of Agriculture and Technology; Prof. Shigeyasu Akai, Kyoto University; Prof. Iwao Hino, Yamaguchi University; Dr. Yoshikazu Nishikado, Director, the Nishikado Mycological Institute, formerly Prof. of Okayama University. Entomologists.—Prof. Toichi Uchida, Hokkaido University; Prof. Masatoshi Nittoh, Tokyo University; Dr. Yoshihiko Kurosawa, Cu- rator, National Science Museum; Prof. Teiichi Okutani, Hyogo Agri- cultural College; Asst. Prof. Magoshiro Moritsu, Yamaguchi University. At the start of this research, we focused our attention on the follow- ing kinds of trees as the main objects for the investigation: Acacia dealbataand A. mollissima, Eucalyptus robusta and EL’. globulus, Popu- lus spp.. Laria europaea and L. dahurica, Picea excelsa, and Pinus spp. (banksiana, elliottii, koraiensis, palustris, radiata, rigida, strobus, sylvestris, and taeda). The researchers have made steady progress during the past 2 years. Recently, Prof. N. Hiratsuka presented an intermediate report of the results obtained in 1959 to the Forestry Agency. According to this report, the research members collected 475 specimens of diseases and 3855 specimens of injurious insects from various regions. The identifications are not yet completed. While this joint research was being carried on, the forest patholo- gists and entomologists in the Government Forest Experiment Station were also working on the same studies in cooperation with the joint research group. Annually a meeting has been held to discuss the re- sults obtained and to facilitate further studies on them. From these investigations, it became clear that we inust pay more careful attention to the following diseases. Poplar diseases. Dieback of poplars caused by Diaporthe medusae Nit. prevails in Honsyu, the middle part of Japan. Dieback and canker caused by Cytospora chrysosperma and Leucostoma nivea oc- curs in Hokkaido, the northern region of Japan. Among five kinds of rust diseases, leaf rust caused by Melampsora larici-populine Kleb. is the most common and serious. JJarssonia brunnea (E. & Ev.) Magn. attacks leaves and young shoots. Poplars belonging to the sec- tions Aigeros and Tacamahaca are severely damaged. Septotis popu- liperda (Moesz & Smarods) Wat. & Cash which causes the leaf blotch a believed to have been introduced with cuttings imported from abroad. Acacia diseases. Glomerella (Physalospora) acaciae Ito & Shibu- kawa causes very severe damage to nursery stock. Eucalyptus diseases. Damping-off caused by Pythium, Fusarium, Rhizoctonia, and Cylindrocladium are very severe. Larch diseases. Shoot blight caused by Physalospora laricina Sa- wada is very dangerous in northern regions of Japan. I shall report further on this disease later on. Larix europaea and L. dahurica are very susceptible. Pine diseases. Pinus sylvestris is very susceptible to Cronartium quercuum. Young plantations of P. strobus are sometimes attacked ceemm ee ay eT DANGEROUS INTERNATIONAL FOREST TREE DISEASES 5 by four kinds of needle rust very severely and also by Armillaria root rot. Nursery stocks of P. radiata are very heavily attacked by /7- plodia pineae. P. radiata, P. canariensis, P. nigra, P. luchuensis, P. strobus are very susceptible to the leaf blight caused by Cercospora densiflorae Hori & Nambu. Among many exotic pines, Pinus strobus is one of the most promis- ing in Japan and is now planted everywhere in this country. The plantation area will be increased year by year. In this situation of plantation planting with this exotic, the forest pathologists must ex- ercise utmost precaution against the occurrence of blister rust. Need- less to say, we must establish whatever effective countermeasures are necessary to prevent the introduction of this disease from abroad and as quickly as possible. While this work is still going on, it is considered very necessary to make a thorough survey in order to ascertain whether the fungus Cronartium ribicola is present or not on native Ribes spp. in Japan, although we have not been aware of the occurrence of the blister rust on Japanese native five-leaved pines. Pathologists of the Government Forest Experiment Station, Hok- kaido University, and Tokyo University searched for C. rzbicola on wild and cultivated Ribes spp. throughout Hokkaido in 1959. Dur- ing this cooperative survey they collected some Cronartium growing on some /?7bes from several parts of Hokkaido. It is uncertain whether the collected Cronartium is exactly the same as the true C. ribicola al- though the fungus seems very similar to the latter morphologically. This important question remains to be solved quickly. This is my report covering the past 3 years. I will take this opportunity to express our sincere gratitude to Prof. N. Takahashi who did so much to establish the foundation of our Working Group. He retired from the representative position of the Group in Japan and recommended me in place of him in June last year. I shall make every effort to accomplish the significant objective of this international cooperative investigation on the forest disease prob- lem, keeping close contact with the forest pathologists in Korea and China with whom I, to my regret, have not yet been able to get an opportunity to talk over the activity of the Working Group. India B. K. Baxsnrt Head, Division of Forest Protection, Forest Research Institute, New Forest (Dehra Dun), India Reports for India have been prepared on the parasitic fungi on Pinus, Populus, and Quereus and on the exotic forest trees that have been successfully established in India. Requests were sent to the fol- lowing countries for information on the diseases of Pinus, Populus, and Yuercus: Burma, Cambodia, Ceylon, Indonesia, Laos, Malaya, Pakistan, Philippines, Singapore, Thailand, and Vietnam. Pakistan responded with a list of the parasitic fungi on Pinus and Quercus; Burma with a list of the species of Pinus occurring naturally in that country, with the notation that no information is available on diseases; and the Philippines with a brief report on the diseases of the two species of Pinus in that country. The remaining countries replied 6 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 that no pertinent information was available. In this report on the parasitic fungi on Pinus, Populus, and Quercus in India, the diseases will be rated as follows: XX X-Dangerous, XX-May be dangerous, X-Not dangerous. Pinus Six species of Pznus occur in the forests of India: (1) P. armandi Frauchet, a Chinese pine, which occurs in northeastern parts of India, (2) P. gerardiana Wall. ex Lamb, localized in NW. Himalayas, (3) P. insularis Endl., in E. India, Upper Burma, and Philippines, (4) P. merkusti Jungh & De Vr., a tropical pine in Far East, (5) P. rox- burghi Sargent, and (6) P. wallichiana Jack., the last two essentially Himalayan. Diseases are known for only three of the species. They are as follows: 1. Pinus insularis Endl. (Khasya pine). Eastern Distribu- tion—Khasia and Naga hills, Manipur, Upper Burma, and Philip- pines. Fomes pinicola Swartz. ex Fr. (XX) Attacks standing trees, causes brown cubical rot. Peridermium sp. (XX) The infection results in large woody out- growths or galls on stem. The alternate host of the rust is not yet known, but is believed to be Quercus griffithi on which III develops. 2. Pinus roxburghii Sargent (Chir pine). Distribution: Outer ranges of Himalayas, and on ridges of the Siwaliks flanking the Himalayas, Bhutan in the east to Afganistan in the west. Capnodium pint Berk. and Curt. (X) Coleosporium campanulae (Pers.) Lev. (X) A heteroecious needle rust, 0 and I on needles of chir, II and III on Campanula colorata Wall. Cronartium himalayense Bagchee (XXX) A heteroecious stem rust, 0 and I on 3 needle chir pine, IT and III in Swertia spp. Fomes annosus (Fr.) Cke. (XX) Fomes pini (Thore) Lloyd (XX) Fomes pinicola Swartz. ex Fr. (XX) Attacks standing trees, causes brown cubical rot. Ganoderma applanatum (Pers.) Pat. (X) Ganoderma lucidum (Leyss.) Karst. x} Lophodermium pinastri (Schrad.) Chev. (X Causes needle cast. Pestalotia funerea Desm. (X) On needles. Polyporus schweinitzii Fr. (X) Causes brown cubical rot in butt portions. Septoria pisi Berk. (X) Causes leaf spot. 3. Pinus wallichiana Jackson (blue pine). Distribution: Throughout temperate region of the Himalayas, chiefly at 6,000- DANGEROUS INTERNATIONAL FOREST TREE DISEASES 7 10,000 ft., sometimes ascending to 12,000 ft., and descending to 4,000 ft. Absent in Sikkim and many areas in Kumaon. Armillaria mellea (Vahl.) Quel. (X) Capnodium pint Berk. & Curt. (X) Coleosporium barclayense Bagchee (XX) A heteroecious rust, 0 and I on 5-needled blue pine, If and III on Senecio spp. Cronartium ribicola Fischer (XX) A heteroecious stem rust, 0 and I on 5-needled blue pine, II and [II on Ribes. Fomes annosus (Fr.) Cke. (XX) Fomes fomentarius (lu. ex Fr.) Kickx (X) On dead wood. Fomes pini (Thore) Lloyd (XXX) Lophodermium pinastri (Schrad.) Chev. (X) Causes needle cast. Melampsora oblonga Bagchee (X) Causes needle rust. Polyporus schweinitzii Fr. (X) On dead wood. Polyporus tomentosus FY. (X) The fungus occasionally attacks blue pine. The parasitic form is referred to as P. tomentosus var. circinatus. Populus There are six species of poplars in India, either indigenous or in- troduced of which Populus ciliata Wall. and P. euphratica Oliv. are the most important. The others, like P. nzgra Linn. and P. alba Linn., are planted for shade or ornament or are quite local. 1. Populus alba Linn. Distribution: Western Himalayan at 4,000-10,000 ft. extending west to Europe, in the Mediterranean and north to Siberia. Melampsora rostrupii G. Wagner (X) II and III on undersurface of leaves; I is not known in India. 2. Populus ciliata Wall. Distribution: Himalayan from Kash- mir to Bhutan, at 4,000-10,000 ft. Boerlagella effusa Syd. and Butler (X) On wood and decorticated branches. Cytospora chrysosperma (Pers.) Fr. (XX) On branches. The Cytospora stage flourishes best during a wet summer. The Va/lsa stage may be found in plenty on the thicker branches in autumn. Fomes fomentarius (Li. ex Fr.) Kickx (X) Linospora populina (Pers.) Schr. (X) On leaves. Melampsora ciliata Bare. (X) II and III on undersurface of leaves; I is not Nectria cinnabarina (Tode) Fr. (XX) On branches. Taphrina aurea (Pers.) Fr. (X) On leaves. 8 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Uncinula salicis (DC.) Wint. (XX) On leaves. 3. Populus euphratica Olivier. Distribution: In Sind (Pak- istan) along the Indus River, southern Punjab along the Sutlej River, Beluchistan, Ladakh, Tibet, ascends from plains up to 13,500 ft. Westwards it extends to Afganistan, Turkistan, Persia, Mesopotamia, and Palestine. Cytospora sp. (Probably C. chrysosperma) (X) On branches. Quercus Indian oaks occur in the Himalayas. Of a total of about 10 species in the eastern Himalayas, the most important are Quercus lamellosa Sm., QV. pachyphylla Kurz, Q. lineata Bl., and Q. spicata Sm. Of the 5 species in the western Himalayas, Y. incana Roxb., Q. dilatata Lindl., and Q. semecarpifolia Sm. are important. 1. Quercus dealbata Hook. Fils. & Th. Distribution: Bhutan, Khasi hills, Manipur. Bispora catenula (Lev.) Sacc. (X) On leaves. 2. Quercus dilatata Lindl. Distribution: Western Himalaya from Nepal westwards, chiefly at 7,000-9,000 ft. Fomes fomentarius (lL. ex Fr.) Kickx (XX) Attacks living but more commonly dead stand- ing and fallen logs. Causes white spongy rot with black zone lines. Fomes rimosus Berk. (X) A wound parasite ; attacks both living and dead wood in which white stringy rot is produced. Lenzites repanda (Mont.) Fr. (X) On stems; rare. Polyporus cuticularis (Bull.) Fr. (X) On dead wood. | Polyporus obtusus Berk. (XX) } A wound parasite. Causes heart and sap rot (white spongy rot). Pucciniopsis quercina Wakef. (X) On leaves. | 3. Quercus grifithi Hook. f. Distribution: Bhutan, Assam ‘ hills, hills of Burma east of Irrawaddy and Sittang. Cronartium spp. (X) IIT on leaves. 0 and I which occur on Pinus insularis may be the alternate stages. 4. Quercus incana Roxb. Distribution: Western Himalayas, extending eastward to Nepal, chiefly in outer ranges at 4,000— 8,0000 ft. Armillaria mellea (Vahl.) Quel. (X) Bulgaria polymorpha (Oed.) Wett. (X) Causes stem canker. Diplodiella crustacea Karst. (X) Causes dieback. Fomes caryophylli (Rac.) Bres. (X) Causes heart rot. DANGEROUS INTERNATIONAL FOREST TREE DISEASES 9 Fomes senex Nees & Mont. (XX) A wound parasite on living and also on dead trees. Pestalotia saccardoi Speg. (X) Polyporus cuticularis (Bull.) Fr. (X) On dead wood. 5. Quercus lineata Bl. Distribution: Eastern Himalayas, at 6,000-9,000 ft., Khasi and Naga hills (Assam), hills of Upper Burma. Fomes pinicola Fr. (X) Fomes senex Nees & Mont. (XX) A wound parasite. 6. Quercus semecarpifolia Smith. Distribution: Throughout Himalayas, Assam-Burma frontier, China. A high altitude oak, usually at 8,000-12,000 ft. Bulgaria inquinars Fr. (X) Causes stem canker. Fomes fomentarius (i. ex Fries) Kickx (XX) On living trees and also on dead wood. Causes white spongy rot with zone lines. Fomes rimosus Berk. (X) A wound parasite on stems. Causes white stringy rot. Polyporus consors (Berk.) Stev. (X) On stems, causes white fibrous rot. Polyporus cuticularis (Bull.) Fr. (X) On butts of trees, fruiting on wound scars. Causes white stringy rot with chocolate- colored to black zone lines. Polyporus gilvus Schwein. (X) Polyporus obtusus Berk. (XX) On living and dead trees. Usually a wound parasite. Causes white spongy rot. Polyporus sulphureus Fr. (XX) Causes brown cubical heart rot. Polyporus versicolor (I..) Fr. (X) Causes white spongy rot with light brown zone lines. Stereum princeps Jungh. (XX) A common wound parasite. Causes white pocket rot. 7. Quercus sp. Distribution: Not reported. Lasiobotrys elegans (Syd.) Theiss. (X) Leucoconis erysiphina Syd. (X) On leaves. Phyllosticta exigqua Syd. (X) On leaves. Trichothyriella quercigena (Berk.) Theiss. (X) On leaves. Hydnum erinaceus Bull. (X) Successful Exotics in India Extract from “Exotics in Indian Forestry Practice” by S. K. Seth and S. N. Dabral. Proc. IX Silvie. Conf. (Part II), Dehra Dun, India, pp. 72-80. 1956. 10 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939. Name of the species The states in which found successful Acacia abyssinica___-------- Bihar (Palamau, Naterhat plateau). Al QECUrT ens =. Sune wees Madras and Uttar Pradesh hills. A. melanonylon__.------_- _. Madras (Aramby block). AM mollissima: == 2a es ee Assam, Himachal Pradesh, Madras (Nilgiris), and Uttar Pradesh (hills). Astpycnanthaut <1 saee hee Uttar Pradesh and Madras hills. Acer negundos . sxc ee) Jammu and Kashmir. Aloicew falcata... 22 ae: Assam. PAVERS J OnUU = 2 ae eee ceneers Pradesh (Solan), Madras (Top Slip, Ootacamund and Wy- naad Centres), Uttar Pradesh, lower hills and submountain areas. VAATUOWUECIVO Ss ae ain Oe ae Himachal Pradesh (Solan hills), Ut- tar Pradesh in submountain re- gions. AlnUsmncana._—— 2. ine Bengal (Takdeh, Lingding, Raman). Broussonetia papyrifera__-_-_- Bengal (Bamanpokri), Bombay (Shahpur, Dandeli, Haliyal, Tere- alli, Donga), Madras (Begur, Top Slip) , Uttar Pradesh (moister areas in Bhabar and Dun). Callitris rhomboidea____---- Madras (Nilambur, Aramby block). Castanea satiwa-2 221 Naya Himachal Pradesh, Punjab (Manali). Castelloa elastica2 a e Bengal (Takdeh). Casuarina jhunghuhniana___ Madras (Chenglepat division). C Mont andadan edad ie an Madras (Nilgiris). C. quadrivalyise. 22.) sy eiagh Madras (Carinhill blocks). Catalpa japonica. 222s. eee Jammu and Kashmir. Chamaecyparis lawsoniana___ Bengal (Takdeh). Ovobtusa. saison) pai pee hE Punjab (Manali). Chlorophora excelsa_____---- Madras in mixed deciduous forests, Assam, Sylhet division, Lawacherm plantation. Cocos coronatas.22. 2 252280 Bombay (Poona, Bhanubundra, Dona). Cryptomeria japonica___---- Bengal (Pagalhora), Madras (Carin- hill block), Punjab (Rahini, Kulu). Cupressus arizonica___.----- Jammu and Kashmir. O. -cashmiriang 2 Sis 2e aes Bengal (Takdeh). C. horizontals». 2... hn ieee Bihar (Palamau). OMuisttanica 2) int Rae ee Bengal (Takdeh), Bihar (Palamau, Naterhat plateau). 0. MACTODOO Ca. es Lae Bihar (Palamau, Naterhat plateau). GP TAT 2s eee PR TE ale Bengal (Takdeh). OC SFomuilasgien 08. lane aaa Bengal (Takdeh), Madras (Nilgiris), Punjab (Manali). Enterolobium saman_------- Bengal (Bamanpokri). Eucalyptus citriodora__-----. Bombay (Londha, Haliyal, Dandeli). Hi GLOO UNIS es Sacadeh rs Aes Madras (Nilgiris). Ee mac ubatd telaet Late Bombay (Shahpur). Ee GONCECOMNTS ta mime ee Os Assam. Hagus sylvatica eee eee Punjab (Kulu, Manali). DANGEROUS INTERNATIONAL FOREST TREE DISEASES ll Name of the species Fraxinus excelsior_____-_---~-.- Hevea brasiliensis___-------- Juniperus virginiana___----- Khaya anthotheca__--------- cpg pe 131 | eee ea a oe me sencyalensiss | Michie afrecang 2s faerie decidual 2S Seng gs 2) Ly Ses ial Me de nati te Peawemplteré a) >>. 2 Ng ee Laucaena glauca___.._--.--~- | Ochroma lagopus__---------.- S12 A le a SS ee eee men irene: 83 Se Fie To: MRE CAIEL 5005 eee conn 2, ce a 58 OS | Populus boroliensis__..--__- Ne Ee, ee 2D fi. NT ee ee ee Manet pera) 2s Sts! (i | a EAT Pseudotsuga taxifolia______- Guercus suber ie | 687-137 O—63———2 The states in which found successful Jammu and Kashmir, Punjab (Kulu, Manali). Bengal (Sukna). Bengal (Takdeh). Bombay (Dandeli). Bombay (Dandeli, Poona, Shahpur, Bhiltar, Lingmala). Bombay (Dandeli, Shahpur, Poona, Binllu, Donga, Haliyal). Bengal (Sukna). Punjab (Kulu division, Manali, Pinet- um, Nagani, Rahini). Punjab (Kulu, Manali, Rahini, etc.). Punjab (Kulu, Manali, Rahini, etc.). Punjab (Kulu, Manali, Rahini, etc.). Assam, Himachal Pradesh, Madras and Uttar Pradesh. Madras; in all research centres of Madras, Wynaad, Southern Kanara, Palaghat, Nilambur, S. Coimbatore. Jammu and Kashmir. Assam. Jammu and Kashmir. Bengal. Madras (Nilambur). Bengal (Raman), Punjab (Manali, Kulu). Bihar (Palamau, Naterhat plateau). Bengal (Raman). Bengal (Raman), Bihar (Palamau, Naterhat plateau), Punjab (Kulu, Manali). Punjab (Kulu, Rahini, Manali). Assam. Punjab (Kulu, Manali, Pinetum). Punjab (Kulu, Manali, Pinetum). Bengal (Takdeh, Samunden). Uttar Pradesh (Chakrata 4500’). Uttar Pradesh (West Almora 6000’). Punjab (Kulu, Manali, Pinetum). Punjab (Kulu, Manali, Pinetum). Uttar Pradesh (Chakrata 4500’). Bombay (Donja, Poona, Khandesh, Dandeli), Madhya Pradesh, (West Berar), Himachal Pradesh (between 2000-3000’), Madras (in dry fuel forests), PEPSU, Rajasthan (all through). Punjab (Kulu, Manali, Rahini, Naga- ni, Nakas). Uttar Pradesh (6000-7000), growth is very slow. 12 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Name of the species The states in which found successful Robinia pseudoacacia__----- Bihar (Naterhat plateau, Palamau), Jammu and Kashmir and Himachal Pradesh (6000-9000’ ). IS CL: COCTULED, 2 = Fe Himachal Pradesh, Jammu and Kash- mir. Swietenia macrophylla___--- Bengal (the species is doing very well all over), Bombay (Dandeli). SEO G ON ta Bie See Bombay (Donga, Poona, Khandla, Dandeli). LWNTOMCWUEODUC Carts 2 = Punjab (Manali, Pinetum). Thajae gigantea... = _ ye Bihar (Palamau). TSOVICTILOUIG Does ris we Bihar (Palamau). Ti DUC ae ie we Ae Bengal (Raman), Punjab (Kulu, Ma- nali, Rahini, Mahangarh, Dharm- sala). Pakistan A. H. Kuan Forest Botanist, Pakistan Forest Institute, Peshawar, Pakistan In this report on the parasitic fungi on Pinus and Quercus in Pak- istan, the diseases will be rated as follows: XX X—Dangerous, X X— May be dangerous, X—Not dangerous. Pinus The genus Pinus is represented in Pakistan by three species: (1) P. roxburghii Sargent, (2) P. wallichiana Jackson, and (3) P. gerar- diana Wall. ex Lamb. The known diseases of the former two species are given below. 1. Pinus roxburghu Sargent (Chir pine) Coleosporium campanulae (Pers.) Lev. (X) A needle rust which may be serious at times, causes early shedding of needles. Cronartium himalayense Bagchee (XX) Rare due to dry situation where the pine grows. Fomes annosus (Fr.) Cke. (XX) Damage is not significant, except in very moist localities. Fomes pini (Thore ex Fr.) Karst. (XX) Rare. 2. Pinus wallichiana Jackson (blue pine) Armillaria mellea (Vahl.) Quel. (XX) Causes root rot with white stringy decay in wood. Cenangium ferruginosum (Fr.) Fr. (XX) Kills young plants, about 10 years old, in moist localities. Coleosporium barclayense Bagchee (X) Causes early shedding of needles. Cronartium ribicola Fischer (XX) The fungus is too rare to be of any consequence. Dasyscypha fusco-sanguinea Rehm emend Hohnel. (XX) Kills young plants. DANGEROUS INTERNATIONAL FOREST TREE DISEASES Fomes annosus (Fr.) Cke. Damage is not significant, except in very moist localities. Fomes pint (Thore ex Fr.) Karst. A serious disease causing heart rot. Fomes pinicola Swartz. ex Fr. Attacks standing trees, causing brown cubical rot. Leptostroma ahmadi Petr. On needles. Lophodermium pini-excelsae Ahmad Causes needle cast in moist and shady localities. Peniophora gigantea (Fr.) Mass. On dead wood. The fungus is a primary colonizer of dead stumps in preference to Homes annosus (Fr.) Cke. Polyporus gilvus (Schw.) Fr. On roots, rare. Polyporus schweinitzii Fr. Causes butt rot. Polyporus versicolor (.) Fr. Causes white spongy rot. Stereum purpureum Pers. Wound parasite. Causes white spongy rot. Quercus 13 (XX) (XXX) (XX) (X) (X) (X) The genus Quercus, in Pakistan, is represented by 5 species: (1) Q. dilatata Lindl., (2) Q. ilexw Linn, (3) Y. incana Roxb., (4) Q. seme- carpifolia Smith, (5) Q. gluca. The diseases of the first four are given below. 1. Quercus dilatata Lindl. Amphisphaeria fallax de Not. On bark. Colpoma quercinum Wallr. Coryneum umbonatum Nees Causes girdling of twigs. Dasyscypha indica (Cash) Ahmad Causes canker on which fruit bodies appear. Discosia atrocreas Tod. ex Fr. Causes leaf spot. Fistulina hepatica Huds. ex Fr. Fomes fomentarius (L.) Fr. Wound parasite. Causes white spongy rot. Fomes pectinatus Klotz. Causes white pocket rot in oak. Fomes rimosus Berk. Fomes torulosus Pers. ex Lioyd Causes heart rot. Ganoderma applanatum (Pers.) Pat. Ganoderma lucidum (WLeyss.) Karst. Nummularia bulliardi Tul. Causes dieback. Penzigia quercum Mueller and Ahmad Polyporus cuticularis Bull. ex Fr. Causes heart rot. (X) (X) (X) (XX) (X) (X) (XX) (X) (X) (X) (X) (XX) (xx) (X) (X) 14 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Polyporus squamosus (Huds.) Fr. (X) Causes brown cubical heart rot. Stereum purpureum Pers. (X) Wound parasite. Causes white spongy rot. Trabutia quercina (Fr. & Rud.) Sacc. & Reun (X) Causes leaf spot. 2. Quercus lex Linn. Amphisphaeria striata Niessl (X) 3. Quercus incana Roxb. Fomes fastuosus Lev. (X) Fomes pectinatus Klotz. (X) Causes white pocket rot. Fomes scruposus (Fr.) Cunn. (X) Wound parasite, causing white spongy rot in heart- wood. Fomes semitosus Berk. (X) Fomes senex Nees & Mont. (X) Causes heart rot. Ganoderma lucidum (Leyss.) Karst. (X) Nummularia bulliardi Tul. (X) Causes dieback. Polyporus hispidus (Bull.) Fr. (X) Causes heart rot. Polyporus schweimitzeu Fr. (X) Causes brown cubical rot. 4, Quercus semecarptfolia Smith Fomes senex Nees & Mont. (X) Philippines Tipurcio S. SEREVO Assistant Director, Bureau of Forestry, Department of Agriculture and Natural Resources, Manila Pinus There are two indigenous species of pines in the Philippines; namely, Pinus insularis Endl. and Pinus merkusii Jungh. & Devr. The following diseases are known for these species: 1. Pinus insularis Endl. (Benguet pine) The pure Benguet pine forest in the Philippines forms a distinct forest type (pine type) in the highlands of northwestern Luzon Island at elevations ranging from 500 to 2,500 meters above sea level but is best developed at elevations ranging from 900 to 1,500 meters. It is reported to exist also in Indo China, Burma, and India. Fusarium sp. Dangerous Causes damping-off. Rhizoctonia sp. Dangerous Causes damping-off. Trametes sp. Unimportant Causes wood rot. Fomes sp. Unimportant Causes wood rot. DANGEROUS INTERNATIONAL FOREST TREE DISEASES 15 Damping-off caused by Rhizoctonia spp. and Fusarium spp. is a com- mon disease of nursery seedlings of Benguet pine in the Philippines. Two- to six-weeks-old seedlings are most susceptible to this disease. Effective control measures found by experiments are: 40% sulfuric acid (H.SO,) diluted in 1,000 cc. of water applied to every square foot of seedbed immediately after sowing the seeds; control of the density of sowing because too dense sowing favors the occurrence of the disease; formaldehyde (40% U.S.P.) diluted with water six times its volume used for treating the soil; and zinc oxide or red copper oxide as soil dressing, the former being more effective. Fungi of the genera 7rametes and Fomes have been observed to infect old and large trees over 60 cm. d.b.h. 2. Pinus merkusti Jungh. & Devr. (Mindoro pine or tapulau) This species occurs in Zambales province and Mindoro Island in places as low as 100 meters altitude. It is reported to exist also in Burma, Indo China, Borneo, Thailand, and Sumatra. There is no disease so far reported or observed affecting this species. Burma H. G. Hunpiey Silviculturist, Rangoon, Burma Pinus The following species of Pznus occur naturally in the forests of Burma: Pinus insularis Endl. (P. khasya Royle.) The Khasi pine. Dis- tribution: Hills of Upper Burma, ie., the Chin Hills, the Pakokku Hills and between the Sittang and Salween Rivers and the Shan States. Chipwi valley, Hpimaw fort and Ngawchang valley in the Kachin State 2,500 feet a.s.l. upwards. Pinus merkusi Jungh. The Tenasserim pine. Distribution: Southern Shan States southward through the hills of the Salween and Thaungyin drainages. 500 to 2,500 ft. a.s.l. P. armandi Franchet. Armand’s pine. Distribution: Panwa and Hpimaw pass, Kachin State. P. wallichiana A. B. Jacks (P. excelsa Wall.) The Blue Pine. Distribution: Lukpyi in Kachin State. Exotic species of Pinus growing in the Botanical Gardens, Maymyo are: P. roxburghii Sarg. (P. longifolia Roxb.) The chir pine. P. caribaea Morelet. The Cuban pine. P. halepensis Miller. The Aleppo pine. P. halepensis Miller var. Orutia (Tenore) Elwes & Henry. The Calabrian pine. None of these have so far been successfully raised in plantations. No research appears to have been done on the diseases of pine. While at Maymyo I have noticed cases of witches’-broom on P. Postwar Quercus No research appears to have been done on the diseases of Quercus of which there are at least 40 species occurring in Burma. ACCOMPLISHMENTS: EUROPE Yugoslavia M. M. Krstic Professor, Forestry Faculty, University of Belgrade, Belgrade, Yugoslavia My principal activity since the creation of the Working Group has been surveying and checking important forest pathogens on Pinus, Quercus, and Populus in some of the countries of southern and eastern Europe. Because of the variety of forest conditions and the different research organizations in these parts of Europe, it has not yet been possible to cover the entire area as originally proposed. Personal contacts have been established with Dr. Biraghi, Chairman of Section 24, IUFRO, and later with Dr. Lohwag (Austria), Mr. Leontovye (Czechoslovakia), and Dr. Kailidis (Greece). During this 3-year period, I have checked pathogens in Czechoslovakia, Greece, Italy, and Yugoslavia; the other forestry ranges will be checked during the next period of time. A completed list of the diseases present in south- ern and eastern Europe can be expected later, as a cooperative work, I believe, with Dr. Lohwag. Asa result of this work to date, several pathogens can be designated as specific for this part of Europe and as dangerous to other countries. Some additional organisms are also more or less common in northern and western Europe. The selected pathogens on Pinus, Quercus, and Populus in southern Europe are the following: Pinus Cronartium asclepiadeum (Willd.) Fr., agent of cortical rust on dif- ferent 2-needle pines, mainly on Pinus nigra, P. sylvestris, and P. halepensis. Melampsora pinitorqua Rostr., a heteroecious fungus causing curv- ing and dying back of new pine shoots, mostly on Pinus nigra and P. sylvestris. Alternate hosts are Populus alba and P. tremula. Actinothyrium marginatum Sacc., an agent of red spots on pine needles, mostly on Pinus nigra and P. sylvestris. The infected needles are shed prematurely. Cenangium abietis (Pers.) Rehm, a cause of dieback of Austrian and Scotch pine twigs under specific climatic conditions. Phacidium infestans Karst., the snow blight fungus on Scotch pine, causing death of young plants. Quercus Microsphaera alphitoides Griff. & Maubl., well-known oak mildew, concurring in dying back of many oaks, and especially of Quercus pedunculata. 16 DANGEROUS INTERNATIONAL FOREST TREE DISEASES 17 Polyporus dryophilus Berk., causing white pocket rot of oak heart- wood, with a considerable loss in wood volume. Loranthus europeus Jacq., a mistletoe with yellow fruits, contribu- ting in oak dying back. Populus Dothichiza populea Sacc. & Br., a widespread parasitic fungus, causing necrosis of bark tissue of many poplars, and generally high mortality of 2- to 3-year plants. Venturia populina (Vuill.) Fabr., producing withering of suc- culent shoots of black poplars in nurseries and plantations. Venturia tremulae Aderh., producing similar effects as the preced- ing organism on Populus tremula, P. alba, and varieties of the latter species. Melampsora allii-populina Kleb., a widespread heteroecious fungus, causing rust and premature defoliation of poplar leaves, mainly on species, cultivars, and clones belonging to the section Aigeiros. “Brown spot disease” is to be added although its true agent still remains unknown. The phenomenon is particularly pronounced in euramerican cultivars, but occurs in native poplars also. It spreads continually. Other work I did was to register those pathogens dangerous to the other native and foreign tree species grown in the south. The recent trend toward the establishment of test plantations of intro- duced fast-growing species such as pine. oak, larch, and Douglas-fir varieties in a number of southern countries will soon provide better information on the susceptibility of these species to native diseases. Observations until now have been made only in the few existing plan- tations and sometimes only on the rare individual. The identity of native pathogens found on foreign trees will be included in the com- pleted list of pathogens of southern and eastern Europe. Czechoslovakia Avec. KALANDRA Ordinary Member, Czechoslovakia Academy of Agricultural Sciences. Zbraslav-Strnady, CSSR Only a few different introduced tree species are used in Czechoslovak forestry. Some of the larger forest stands in Bohemia are composed mainly of the introduced Pinus strobus which reaches mean or older age. Larix leptolepis is grown more frequently but not ona large scale. Introduced spruces are not grown on a large scale either. Douglas-fir has been and still is in high favor. In more recent years Abies grandis has been tried. Among the introduced broad-leaved trees, Quercus rubra and Fraxinus americana are represented here and there. Vari- ous North American, European, and Asian species or hybrids of poplar have also been introduced. Diseases known from other countries are important factors in some regions of Czechoslovakia. Cronartium ribicola Dietr. is damaging to Pinus strobus here and there in forests, parks, and where used as an ornamental. White pine was formerly favored in the Elbe region of Bohemia because of its resistance to Lophodermium pinastri 18 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 (Schrad.) Chev. It later became apparent that this species was sus- ceptible to a variety of other diseases, among them the above-mentioned C. ribicola, Armillaria mellea (Wahl.), and Leptostroma strobicolla Hil. Injurious animals increased the damage. For these reasons cul- tivation of white pine is now limited. It is worthy of mention that Cronartium ribicola occurs individually even on the native Pinus cembra in the High Tatra Mountains. Jack pine, Pinus banksiana, was cultivated toward the end of the 19th and the beginning of the 20th century because of its resistance to pine needle cast. Low growth rate of this species at older ages caused a return to the use of Scotch pine, Pinus sylvestris, despite its susceptibility to needle cast. European larch, Larix decidua. suffers severely from Dasyscypha willkommiu (Hart.) Rehm. and more resistant races are being sought. The good qualities of the Sudeten and Tatra larch may be stressed rather than trying to use the very susceptible European larch. It is also planned to take advantage of the resistance of Larix leptolepis in hybridization work. Larch in forest nurseries is attacked by the needle cast caused by Meria laricis Vuill. Experiments should be carried out to test the resistance of various provenances. Douglas-fir is an especially important forest tree species. Rhabdocline pseudotsugae Sydow appeared in the CSSR for the first time in 1938 and is spreading in the existant forest stands of this valuable tree species. Successive attacks on Douglas-fir over a period of several years leads to defoliation and, here and there, to the death of trees. The attacks are quite irregular. This disease has not re- duced the popularity of Douglas-fir even though RAabdocline has spread over large areas in various regions of the Czechoslovak Socialist Republic. Adelopus gaumanni Rohde has not yet been recorded in the CSSR, though it is common in neighboring states (German Democratic Republic, etc.). But Douglas-fir is attacked by the foreign aphid Gilletteella cooleyt Gill. In addition, Douglas-fir suffers lke other tree species from attacks by the honey fungus, Armzllaria mellea. Pinus austriaca is planted artificially on lime and extreme sites. It is more resistant to Lophodermium pinastri but more susceptible to Cenangium abietis (Pers.) Duby, which has spread in our country notably since 1959. It is also more susceptible to Maemacyclus niveus Pers. Broadleaved tree species are represented notably by Quercus rubra. No important diseases are recorded. Foresters are worried by diseases of poplars grown in pure stands after World War II, and mainly from the vear 1955. Our native poplar, Populus nigra f. typica Schneider, suffers heavily from Chondroplea populea, brown spot disease, and other diseases. Im- ported poplars are not immune, but here and there Populus monilifera and Euroamerican poplars suffer less than the native ones. Hybrids used in forestry and outside the forest, such as Populus robusta, P. regenerata, and P. berolinensis, suffer by brown spotting and Chondroplea populea. Pseudomonas rimaefaciens and Nectria do not occur as frequently as in western Europe and other parts of central Europe. Venturia populina (Vuill.) Fabr. attacked the poplar, Populus berolinensis, in one locality. It is not seriously harmful in other places. —_— —- ~~ ——— - - DANGEROUS INTERNATIONAL FOREST TREE DISEASES 19 Investigations of recent years show damage to Italian poplar I-214 and other susceptible poplars by late frosts. Populus stmoni suffers in the CSSR from brown spotting disease and Dothichiza populea (Chondroplea populea (Jacc.) Kleb.) Septoria musiva Peck has not yet been found. Graphium ulmi Schw. damages the elm in forests, parks, and along streets. Foreign elms have not yet been introduced to our country. Czechoslovak forest management relies mainly upon native tree species. Douglas-fir is the only introduced tree species of considerable economic importance. Exotic tree species and their diseases are given more attention in gardening and park management. Great Britain T. R. Peace Formerly Chief Research Officer (Deceased), Forestry Commission, Forest Research Station, Wrecclesham, Farnham, Surrey, England Pressure of existing commitments and staff changes have prevented any substantial developments in forest pathological work in Britain over the last few years. This has inevitably affected our international activities. Probably the most significant piece of work, internationally, was the organization, under the auspices of [UF RO of a meeting of persons actively interested in the fungus Fomes annosus. This was held in Scotland in May 1960, and involved a number of forest excursions as well as meetings; 23 delegates from 9 countries attended including 5 from North America. A report, containing the papers presented by delegates, an account of the field tours, and a summary of the discus- sions, has been prepared and is now with Dr. Biraghi, Chairman of Section 24, who is dealing with the question of publication. A list of fungi attacking the genera Pinus, Populus, and Quercus in Britain has been prepared as part of the general scheme. It is my view that before these lists are finalized more thought must be given to the evaluation of the status of the diseases mentioned. The terms used at present are too vague. In addition, value would be added to the list if degree of susceptibility could be mentioned where sound in- formation is available. For instance, Melampsora pinitorqua has been recorded on Pinus nigra calabrica in Britain, but this record rests on one or two occurrences with negligible damage. Only on Pinus syl- vestris has it so far proved damaging. A good deal of the work currently in progress has a definite inter- national interest. Tests of large numbers of poplar clones for their resistance to bacterial canker and the field testing of elms, including some of those produced in Holland, for resistance against Ceratocystis ulmi are cases in point. The test area of two-needled pines and aspen poplars to get information on susceptibility to Melampsora pinitorqua has yielded some information on American (Pinus resinosa, Populus tremuloides, P. grandidentata) as well as on European species; but it has proved extremely difficult to maintain in an actively infective condition and is being abandoned. In August and September 1960, J. S. Murray made an extensive tour in Denmark, Germany, and Belgium, visiting Research Stations and inspecting diseases in the forest. During the period in Germany 20 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 he received financial help from the West German Bundesministerium, for which we give grateful thanks. This visit resulted in the establish- ment of many useful contacts, and in valuable exchanges of information. ACCOMPLISHMENTS: NORTH AMERICA Canada V. J. Norpin Associate Director, Forest Entomology and Pathology Branch, Department of Forestry, Ottawa, Canada Introduction The progress made in Canada towards the objectives of the Work- ing Group on International Cooperation in Forest Disease Research, Section 24, the International Union of Forest Research Organizations, is summarized under the following headings: Organization of Forest Pathology in Canada, Forest Disease Surveys, Test Plantations of Exotic Trees, Quarantine Measures, Literature Reviews and Publica- tions of International Interest, and Directory of Forest Pathologists. The Organization of Forest Pathology in Canada Research in forest pathology in Canada is undertaken principally by the Forest Entomology and Pathology Branch of the Department of Forestry. Important and significant activities, however, are in progress at other institutions. These agencies are discussed briefly under appropriate headings. Forest Entomology and Pathology Branch, Canada Depart- ment of Forestry.—The Headquarters of the Forest Entomology and Pathology Branch in Ottawa consists of a Director, two Associate Directors, and supporting staff. One Associate Director is responsible for the direction of the national program of research and surveys in forest pathology. Some 60 scientists assisted by approximately 100 laboratory and field technicians are employed at seven regional laboratories located at Victoria, British Columbia; Calgary, Alberta; Saskatoon, Saskatchewan; Maple, Ontario; Quebec City, Quebec; Fredericton, New Brunswick; and Corner Brook, Newfoundland. Within the Forest Entomology and Pathology Branch close work- ing relationships exist between the pathology and entomology groups, with a high degree of integration and interdependence of personnel, Surveys, research investigations, and facilities. In the Forest Insect and Disease Survey program, for example, a number of research officers coordinate insect and disease activities regionally and nationally, and some 75 forest ranger technicians are responsible for field surveys and collections of both diseases and insects. There are joint facilities and personnel for photography, library, biometric guidance, administra- tion, and other services. A primary function of forest pathology in each laboratory is to conduct a comprehensive program of research and regional surveys of forest diseases with the aim that losses caused by disease may be pre- vented or reduced to an acceptable level and thereby improve silvicul- tural and forest management procedures. Close liaison is maintained 21 22 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 with the forest industries, the provincial governments who admini- strate almost 80 percent of Canadian forests, and other associated agencies. The regional laboratories also contribute technical and advisory services to provincial governments and industries in disease control programs, in the application of pathological procedures to inventory and utilization practices, and in the appraisal of the results of control operations. Instruction in forest pathology is frequently provided to universities and forest ranger schools. Other Federal Government Departments.—In the Department of Agriculture, the mycology unit of the Plant Research Institute conducts taxonomic studies of fungi and provides identification serv- ices. The work of Dr. M. K. Nobles with wood-destroying fungi is of particular interest to forest pathologists. This institute is also respon- sible for frost resistance studies relating to trees. In the Forest Products Research Branch, Department of Forestry, research is undertaken at both the Ottawa and Vancouver laboratories on stain and decays of wood products in storage and service. Provincial Governments.—The provincial forest services provide experimental areas, building sites, and transportation services; their personnel cooperate in forest insect and disease surveys and frequently participate in research projects with the Department of Forestry and other agencies. Forest pathologists will be interested to learn that many provincial governments now obtain information on decays as a regular part of forest inventories, with the Forest Entomology and Pathology Branch staff contributing guidance in field and laboratory techniques. Universities——An important contribution of the universities to forest pathology in Canada is the training and development of re- search personnel. In addition, in forest disease research, Dr. J. E. Bier and his students at the University of B.C. are engaged in studies of bark moisture in relation to the development of canker diseases caused by native, facultative parasites (7). The morphology of dwarfmistletoes is being examined by Dr. J. Kuijt, University of B.C. At the University of Toronto, E. Jorgensen is investigating diseases of forest plantations, particularly root rot caused by Yomes annosus. At Queen’s University, Dr. H. M. Good is concerned with decay organisms of hardwoods and Dr. G. Krotkov is collaborating with Dr. V. Slankis of the Laboratory of Forest Pathology, Depart- ment of Forestry, Maple, Ontario, on studies of mycorrhizae. Research problems of particular interest to the Forest Entomology and Pathology Branch, but requiring facilities not available at re- gional laboratories, are occasionally conducted by university staff members under Department of Forestry extramural research financial grants. Funds for forest disease research at universities may also be provided by agencies such as the National Research Council, On- tario Research Foundation, and the forest industries. International Considerations.—Forest pathologists in Canada maintain close contact with their colleagues throughout the world through correspondence and through participation in F.A.O. work- ing groups, various international committees and societies, attendance at world scientific congresses, and by exchange visits with scientists in other countries. Through the Colombo Plan, scientists of member countries are invited by the Canadian Government to engage in study tours of research programs and facilities. At the present time we DANGEROUS INTERNATIONAL FOREST TREE DISEASES 23 are pleased to have Dr. B. K. Bakshi of India making a detailed study tour of forest disease research establishments throughout Canada. Consultations between Canadian and American pathologists is fre- quent and three international conferences held annually in the eastern, central, and western regions of Canada and the United States provide excellent opportunities for informal discussions of problems. At the first meeting of the newly formed North American Forestry Commis- sion scheduled for Mexico City, July 24 to July 29, 1961, forest diseases constitute an important part of the agenda of business. This new commission will provide increased opportunities for the mutual ex- change of information between pathologists in Canada, the United States, and Mexico and should strengthen the contacts of scientists in North America with those of other countries. Forest Disease Surveys The Forest Entomology and Pathology Branch maintains a per- manent national organization for continuing surveys of forest diseases and insects. The primary objectives of the forest disease survey are to detect, identify, record, and interpret the significance of tree diseases in Canada. This survey establishment includes some 75 forest ranger technicians located in the various regions of the country whose duties are to collect and appraise the damage caused by forest diseases and insects. Forest personnel of provincial governments, industries, and other agencies are active cooperators in this program. These activities are coordi- nated and directed at regional and national levels by research officers. The published results of 10 years (1951-60) work have verified the usefulness of this methodical appraisal of diseases, The results have proved valuable in developing control procedures, in preventing the establishment and spread of new diseases, and in providing a founda- tion for the planning and development of the disease research program. Typical of the recional disease survey contributions included in the Annual Report of the Forest Insect and Disease Survey for 1960 (3) is the report from British Columbia (6). A total of 2,049 disease col- lections were made from more than 40 tree species. Under “Important Diseases,” the following are discussed : weather injury ; foliage diseases caused by Hypoderma deformans, H. laricis, and Rhabdocline pseu- dotsugae; two new diseases introduced from Europe, pine twist rust (Melampsora pinitorgua) and pear-juniper rust (Gymnosporangium fuscum) ; willow blight; dying of weeping willow; Afelampsora rust of Douglas-fir and poplar; diseases of exotic trees; and disease con- ditions in forest nurseries. Under the title of “Other Noteworthy Diseases,” 20 additional diseases are tabulated according to host, or- ganism, locality, and remarks. It is evident that the results obtamed from the survey are of interest to pathologists in other countries be- cause many of the pathogens reported have worldwide distribution. During recent years detailed surveys of native and introduced dis- eases have included the Dutch elm disease, white pine blister rust, root rots caused by Fomes annosus and Armillaria mellea, willow blight, the beech-bark disease, various decay fungi, needle cast and rust fungi, poplar canker fungi, dwarfmistletoes and their parasites, and many others. Special surveys and appraisal studies of diseases of Douglas-fir plantations have been underway for the past few years (4). In 24 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Alberta, ground and aerial surveys of dwarfmistletoes on lodgepole pine were initiated in 1960 to improve the methods of survey and assessment of damage. Compilations of the pathogens of Pinus, Quercus, and Populus have been completed. Six regional reports distributed earlier this year summarize the findings for the extensive regions of Canada covered by each. presentation. These data will be collated and revised in one publication. In addition, a comprehensive report on the diseases of Pinus with detailed annotations on each pathogen is in an advanced stage of preparation. This will be the first in a planned series of de- tailed annotated compilations of the diseases of native and exotic trees and should prove of interest to workers in other countries. A series of descriptive publications covering the diseases of major tree species is envisaged and the first of these dealing with lodgepole pine is in preparation. Test Plantations of Exotic Trees Numerous species of exotic hardwoods and conifers have been estab- lished in plantations throughout Canada during recent years by indus- tries and by provincial and federal governments. Unfortunately, no central agency has the responsibility to collate and ensure the most effective development of these plantings. Also, these plantations have not been grown specifically to determine susceptibility to native dis- eases. As a result, many plantations may not have been located in the environment most favorable for tree growth and resistance to native diseases. Nevertheless, many of these plantations are yielding data on diseases that are recorded in the Annual Report of the Forest Insect and Disease Survey (3). In British Columbia a central registry for all introduced trees and test plantations in the Province has been set up by the Forest En- tomology and Pathology Laboratory, Victoria, and by the B.C. Forest Service (7). This development recognizes the dangers involved in the introduction of exotic trees and the objectives are to register all plantations, appraise disease conditions periodically, assess species suitability, and to prevent the introduction of damaging foreign ciseases. The exotic plantations under observation now total 168 and are generally of recent origin. The 1960 Survey report (3) provides a progress statement on the condition of these plantations. New host-fungus records are tabulated and unfavorable site conditions are suggested to have precipitated a 75-percent incidence of basal canker by Armillaria mellea in a plantation of “Robusta” and “Grandis” poplar hybrids (6). In British Columbia, Ontario, and Quebec various studies on the biology and host-parasite relationships of pathogens of hybrid pop- lars (particularly in the section Leuce) include fungous species in the genera Cytospora, Didymosphaeria, Dothichiza, Gloeosporium, Melampsora, Pollaccia, Septoria, Hypoxylon, and others. In Ontario and Quebec, special surveys are being conducted in test plantations particularly of hybrid poplars established by provincial govern- ments and industries, and reliable inoculation methods are under con- sideration in the assessment of host susceptibility. Standardization of inoculation procedures and host material is needed so that results will be meaningful to all countries. In Ontario and British Colum- bia resistance testing of white pines to white pine blister rust has been DANGEROUS INTERNATIONAL FOREST TREE DISEASES 25 underway for several years and in Quebec tests of resistance of native and European elm hybrids to the Dutch elm disease have been in progress since 1956. Quarantine Measures The Destructive Insect and Pest Act (2) guards against the intro- duction and distribution of destructive forest diseases and insects. This Act is administered by the Plant Protection Division of the De- partment of Agriculture which is empowered to quarantine any for- eign disease that has not become widely distributed. Where a disease is well established, the movement of host material may be restricted to prevent the spread of the disease to other parts of the country. Dutch elm disease is an example of a disease that has become per- manently established. The importation of all plants and products of Ulmus and Zelkova is prohibited unless the material has been kiln- dried under specified conditions. To prevent the spread of the disease within the country, the shipment of elm plants or logs from the east- ern provinces of Ontario, Quebec, and New Brunswick to other prov- inces is not permitted. These regulations are under constant revision according to circum- stances. At present, for example, negotiations are under way to in- clude specific clauses in the Act to prevent the introduction and spread of certain diseases such as weeping canker (bacterial canker) of pop- lar caused by Pseudomonas syringae. Suggestions for the improve- ment of quarantine legislation and procedures are being submitted in the general discussions in Session IV of this symposium. Literature Reviews and Publications of International Interest Literature reviews of forest diseases are generally included as part of publications reporting specific research. In addition, some recent reviews include dwarfmistletoes (5), the diseases of lodgepole pine (10), the diseases of red and white pine (77), and general reviews (8, 9). A list of French and English names of tree diseases in Canada is in press. The annotated list of diseases of Pinus now in preparation will include the pertinent literature on this subject. Further reviews of forest diseases are planned. A number of Canadian reports and publications are of interest to pathologists in other countries. The Annual Report of the Forest Insect and Disease Survey has already been mentioned. The Bi- Monthly Progress Report of the Forest Entomology and Pathology Branch is another publication that provides progress statements on research underway at regional laboratories throughout Canada and in- cludes a current list of scientific publications. An annual list of pub- lications of the Forest Entomology and Pathology Branch on forest diseases is also issued and copies of the listed papers, many of which are of international interest, are available upon request, usually with- out charge. Directory of Forest Pathologists _ A report has been prepared for distribution at this symposium list- ing the names and research interests of forest pathologists of the Forest Entomology and Pathology Branch, Department of Forestry. In addition to this list of Department of Forestry pathologists, other scientists working in the field of forest pathology in Canada are re- 26 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 corded in a separate tabulation. Forest pathologists throughout the world are encouraged to correspond with these scientists. Summary This presentation reports on Canada’s participation in the Working ale on International Cooperation in Forest Disease Research, as ollows: 1. Results from the Forest Disease Survey, which are of interna- tional interest, are published each year. Six regional contributions on the diseases of Pinus, Populus, and Quercus have been completed and distributed. A detailed annotated list of diseases of Pinus is in ad- vanced preparation and similar presentations are to be compiled for the other major tree species. A series describing the diseases of each important timber tree is also in view. Special surveys are being under- taken on the diseases of Douglas-fir and on dwarfmistletoes of conifers. 2. Quarantine measures are being reviewed. 3. Test plantations of exotic hardwoods and conifers established throughout Canada by provincial governments and industries are being examined periodically to determine susceptibility to native diseases. Inoculation tests are also being made utilizing some of the most 1m- portant native pathogens. These tests could be made more meaningful to all countries if inoculation procedures and host material were standardized. 4. Literature reviews are generally included as part of each com- prehensive publication. Also, a number of reports have been made summarizing the diseases of individual trees or the types of pathogens; more of these reviews are contemplated. Current publications of international interest are listed in the Annual Report of the Forest Insect and Disease Survey and the Bi-Monthly Progress Report. An annual tabulation of publications by the Forest Entomology and Pathology Branch lists a number of research contributions of interest to pathologists in other countries. 5. A directory of forest pathologists and their research activities has been prepared and distributed to IUFRO member countries. Literature Cited (1) Bier, J. E. The relation of bark moisture to the development of’ canker diseases caused by native, facultative parasites. V. Rooting behavior and disease vulnerability in cuttings of Populus trichocarpa Torrey and Gray, and P. ‘robusta’. Canad. Jour. Bot. 39: 145-154. 1961. (2) Canada, Department of Agriculture. The destructive insect and pest act and regulations thereunder. Ottawa. 1949. (3) Canada, Department of Forestry. Annual report of the forest insect and disease survey 1960. Forest Ent. and Path. Branch, Ottawa. 1961. (4) Foster, R. E., and Johnson, A. L. S. Forest disease sampling studies in Douglas fir plantations. III. Canad. Dept. Agr., Forest Biol. Div., Vic- toria, B.C. 1960. (5) Kuijt, J. Dwarf mistletoes. Bot. Rev. 21: 569-628. 1955. (6) Molnar, A. C. Province of British Columbia, Forest Disease Survey. In Ann. Rpt. of the Forest Insect and Dis. Surv. 1960. Canad. Dept. Forestry, Forest Ent. and Path. Branch, Ottawa. 1961. and Garman, E. H. Introduction of exotic trees to British Co- lumbia. B. C. Lumberman 42: 36-37. 1958. (7) ee DANGEROUS INTERNATIONAL FOREST TREE DISEASES yA (8) Nordin, V. J. Forest disease research in the foreseeable future. Proc. Forestry Cent. Conf., pp. 23-28, Oregon State College. 1959. Forest disease research trends in Canada. Proc. IX Int. Bot. Congress, Montreal. (In press.) Diseases of lodgepole pine. In Lodgepole pine in Alberta. Canad. Dept. of Forestry Bull. (In press.) (11) White, L. T. Major pine diseases. In White and Red Pine, Ecology, Silviculture, and Management. Canad. Dept. of North. Aff. and Natl. Re- sources, Forestry Branch Bul. 124. 1960. (9) (10) United States Department of Agriculture J. R. HanssproucH Director, Division of Forest Disease Research, Forest Service, UWS. Department of Agriculture, Washington 25, D.C. The U.S. Department of Agriculture has five Divisions—two in the Forest Service, three in the Agricultural Research Service—respon- sible for activities of direct interest to our Working Group. It would be helpful to characterize briefly the responsibilities of these Divisions. In the Forest Service, the Forest Disease Research Division plans and carries out investigations to determine the cause of and to formu- late control methods for diseases of forest trees and forest products, and the Forest Pest Control Division administers all Federal forest disease control programs, including detection and appraisal surveys. In the Agricultural Research Service, the Crops Research Division plans and carries out investigations to determine the cause of and to formulate control methods for diseases of shade, ornamental, and orchard trees; the Plant Quarantine Division administers all Federal quarantines regulating the importation of plants and plant materials, including their fungus and insect pests; and the Plant Pest Control Division administers similar quarantines regulating the domestic movement of plants and plant materials. These five Divisions, there- fore, are responsible for all Federal research and prevention or control programs for tree diseases in the United States. They are head- quartered in Washington, D.C., and cooperate closely in carrying out their work. Progress toward our Working Group objectives by the U.S. Depart- ment of Agriculture may be summarized under a few headings: Re- search, Publications, Quarantines, Exchange of Tree Seed, and Mis- cellaneous Activities. Research In the Department, and primarily in the Forest Service, there are about 100 scientists engaged in some aspect of tree disease research. All major forest tree diseases in the United States are under study to determine their causes, to clarify the taxonomy of pathogens, to estab- lish their diagnostic characteristics in pure culture, to understand the influence of environmental factors on their incidence, and to develop and improve control methods. Control is sought through direct meas- ures such as sanitation or application of fungicides or other chemicals and through indirect measures such as management practices favorable to the tree and detrimental to the disease or selection and breeding for genetic resistance. We also seek to exclude dangerous foreign forest pathogens, a subject I will discuss further under Quarantines. 687-137 O—63 3 28 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939. Of immediate interest, we have many studies in progress on the principal diseases of Pinus, Populus, and Quercus, several of which will be considered in detail. Examples are as follows: Diseases of Pinus spp.— Cronartium ribicola, blister rust of white or 5-needle pines; Cronartium strobilinum, cone rust of southern hard pines; Cronartium fusiforme, fusiform rust of southern hard pines; Cronartitum comandrae, Comandra rust of western hard pines; Peridermium harknessii, gall rust of western hard pines; Scirrhia acicola, brown-spot needle blight of longleaf pine; Elytroderma deformans, needle blight of ponderosa pine; and Fomes annosus, root rot of conifers. Diseases of Populus spp.— Hypoxylon pruinatum, Hypoxylon canker of aspen. Diseases of Quercus spp.— Ceratocystis fagacearum, oak wilt. In addition, we are investigating the heart rots of all species to de- termine the causal fungi, how they enter living trees, how rapidly they decay wood, and the relation of rot volume to tree age, vigor, and site conditions. For all western conifers we are studying the factors that regulate infection and intensification of the dwarf- mistletoes, Arceuthobium spp., which are a major cause of loss in forest productivity. For many diseases, particularly the Cronarteum rusts and the dwarfmistletoes, we are strengthening our research to develop controls with systemic chemicals. Publications Federal research on forest tree diseases in the United States has been carried on continuously since 1899. By the end of 1960 about 2,800 articles had been published on the cause and control of diseases of forest trees and forest products. These were published as govern- ment bulletins, in scientific journals, and in a wide variety of technical, trade, and popular publications: Titles through 1953 are listed in USDA Miscellaneous Publication No. 725, “Bibliography of Forest Disease Research in the Department of Agriculture.” We plan to publish additions to the bibliography at 10-year intervals. In the meantime we issue annual lists of publications such as the one for 1960, available for distribution at this Congress. Instructions on how to re- quest copies of articles are attached. With few exceptions, publica- tions of the U.S. Department of Agriculture are available at no cost. Of the many recent publications on forest diseases issued by the U.S. Forest Service, three by Dr. Perley Spaulding are of particular significance to this Congress. They are USDA Handbooks Nos. 100, 139, and 197, respectively published in 1956, 1958, and 1961. No. 100 is titled “Diseases of North American Forest Trees Planted Abroad” ; No. 139, “Diseases of Foreign Forest Trees Growing in the United States”; and No. 197, “Foreign Diseases of Forest Trees of the World.” In 1955 we started a new series of publications known as Forest Pest Leaflets. To date, 54 leaflets have been issued, of which 26 are on diseases and 28 are on insects, These leaflets summarize for popular DANGEROUS INTERNATIONAL FOREST TREE DISEASES 29 use available information on the cause, hosts, symptoms, distribution, and control of the subject disease or insect. Quarantines In 1912 the Federal Plant Quarantine Act was enacted in the United States to prevent the importation of plant pests. Under this Act there are prohibitions and limitations regulating the importation of woody plants—seed, seedlings, cuttings, or any plant part—that may result in the entry into the United States of injurious plant diseases and in- sects. The importation of 53 woody genera, including 22 genera of forest trees, is prohibited except as seed or for experimental use under rigid restrictions. No plant pest—‘insects, nematodes, bacteria, fungi, other parasitic plants or reproductive parts thereof, viruses, or any similar organisms or infectious substances which can cause disease or damage to plants or plant products’—may be imported from abroad without authorization under a general or specific permit issued by the Department of Agriculture. Under the provisions of this Act, our inspectors, in 1960, intercepted and destroyed about 31,000 poten- tially destructive plant pests, one every 17 minutes. I have no figures on how many of these interceptions were of potential forest pests. In 1960 the U.S. Forest Service formally approved two policies of particular interest to this Congress—one with reference to importa- tion and the other to exportation of woody plants or parts thereof. We will import forest trees or other plants into the United States by seed only, subject to postentry fumigation, except in those cases where the plant cannot be reproduced adequately or exactly by seed, as in clonal lines. In such cases, quarantine regulations will be rigidly ob- served. We will export treated seed only as a means of introducing USS. trees or plants into foreign countries, except in those cases where the plant cannot be reproduced adequately from seed. In such cases, we will inform the importer of the hazards involved and recommend adequate precautions, such as inspection, fumigation, and isolation. Exchange of Tree Seed The Forest Service cooperates with foreign scientific institutions, universities, and public agencies in the collection and exchange of small quantities of forest tree seeds and other forest plant material for re- search purposes. In 1960, for example, we received 116 requests from 39 foreign countries for 603 collections of U.S. forest tree seed. We have filled 337 of these requests and will handle most of the remaining ones in the near future. Also in 1960 we had 19 requests from within the U.S. for 226 collections of foreign forest tree seed, of which 135 have been filled. Involved in these exchanges were seed from one to several species of important forest trees in 24 genera. If this rate of exchange of tree seed continues, or increases as it has in the past few years, and the introduced species are established in plantations, it should provide excellent opportunities to determine the susceptibility of many exotic trees to the diseases of other continents. In making these exchanges we adhere to the policies on importation and exportation of tree seed as set forth in the preceding section. Miscellaneous Activities Special surveys and studies are in progress to determine the relative susceptibility of native and exotic forest tree species to diseases in the U.S. Among such diseases are white pine blister rust (Cronartium rib- 30 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 icola), fusiform rust (C. fusiforme), brown-spot needle blight (Sczr- rhia acicola), annosus root rot (/omes annosus), Hypoxylon canker (Hypoxylon pruinatum), oak wilt (Ceratocystis fagacearum), and dwarfmistletoes (Arceuthobium spp.). Selection and/or breeding to improve genetic resistance to specific forest tree diseases is underway in the following genera: Castanea for resistance to H'ndothia parasitica; Populus for resistance to Septoria musiva; Ulmus for resistance to Ceratocystis ulmi and Morsus ulmi; Juniperus for resistance to Lxosporium glomerulosum and Pho- mopsis juniperovora; Pinus for resistance to Arceuthobium spp., Cronartium ribicola, C. fusiforme, and Phytophthora cinnamon, and Pseudotsuga for resistance to Rhabdocline pseudotsugae. In addition, for all forest tree diseases our pathologists have been directed to note any instances of apparent resistance and to take action as needed to insure that the germ plasm is not lost. A recent development in the United States will stimulate increased international cooperation in forest disease research. The United States sells surplus agricultural commodities—wheat, cotton, and to- bacco, for example—to many countries. Payment for these commodi- ties is accepted in the currency of the recipient country and has re- sulted in the accumulation of considerable U.S. credit balances in some countries. In 1958 we were given the authority by Congress to use a portion of these funds for agricultural and forestry research of benefit to the United States. Since that time we have negotiated 234 foreign research projects, including 48 in forestry distributed as follows: Europe 27, Asia 15, and South America 1. Five of the for- estry projects are in forest disease research. Two are on the role of mycorrhizae in tree nutrition, growth, and disease susceptibility (in Finland and Poland); one is a survey of the diseases of native and exotic conifers (in Spain) ; another is on the antibiotic relationship of saprophytic soil fungi to forest tree root pathogens (in Poland) ; and the remaining one is a study of the susceptibility of North Amer- ican forest tree species to insects and diseases (also in Poland). We | are currently negotiating similar susceptibility studies in Columbia and Uruguay, S.A. These research projects will contribute directly to our Working Group objectives. In conclusion, I would like to say that we in the U.S. Department of Agriculture will take advantage of every opportunity to carry out research at home and abroad that will provide a better understanding of the nature and cause of destructive forest diseases and will lead to improved methods of reducing disease losses. United States As Ja Rime Professor of Plant Pathology and Forestry. University of Wisconsin, Madison, Wisconsin, U.S.A. Studies are under way at Wisconsin on some potentially dangerous diseases. q | DANGEROUS INTERNATIONAL FOREST TREE DISEASES 31 Oak Wilt If oak wilt should suddenly appear in other continents, some of the following control measures might be worth considering. When the infected tree and all other trees within 10 to 15 meters are killed with sodium arsenite, local spread of the disease is stopped. Sodium arsenite must be used with suitable precautions so that ani- mals are not poisoned. This chemical has been effective, but many others have been inadequate or worthless. Where desirable, the local spread may be prevented by cutting the roots between infected and healthy trees or by placing a chemical barrier between healthy and diseased trees with methyl bromide or Vapam injected in the soil. A girdle through at least the last three annual rings may hasten the desiccation of the tree and reduce fungus mat formation. Poplar Cankers Natural and artificial poplar hybrids are under test for resistance to various diseases. Cankers caused by Hypoxrylon. Dothichiza. Septorza. and Fusarium are among the more important. In addition, attention is being given to such problems as wet wood, spring de- fohhation, rust, and dieback. Some of these fungi are well known in Europe and elsewhere. However, we do not vet know whether they are the same races as those which occur in North America. White Pine Blister Rust In addition to the conventional control of white pine blister rust by the eradication of Ribes bushes, research is underway to develop resistant white pines. First generation progenies from controlled crosses with six resistant selections contain a considerable percentage of resistant seedlings. The incidence of white pine blister rust infection in Wisconsin is associated with the microclimate. Silvicultural aids to control can be made on the basis of forest stand microclimates. Descriptions of local climatic situations have been worked out that serve as guides for removal of Ribes bushes only when necessary. They serve also for selecting sites for planting white pine. In some places the danger from the blister rust is great; in others the danger is too small to consider. Such areas may be quite close together. Scions and seed from elite white pines have been sent to a number of places abroad. Dutch Elm Disease Research is underway to reduce the damage from the Dutch elm disease through genetic resistance and with systemic chemicals both against the fungus and against the insect vectors. Seed Collections At the request of Dr. Takahashi, seeds from various Wisconsin species have been collected and forwarded to Japan. The research reported has been done in cooperation with the Wisconsin Conservation Department, the U.S. Forest Service, the Nekoosa Edwards Paper Company, and others. 32 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Summary of Conferences Abroad In 1959-60 Professor A. J. Riker consulted with authorities in | North America, Europe, Southeast Asia, and the South Pacific on what should be done about internaticnally dangerous tree diseases. He went on a Haight Travelling Fellowship from the University of Wisconsin. His study was a part of the work of Section 24 of the International Union of Forest Research Organizations. A summary of the results of his discussions provides the basis for the fourth and last session of our Working Group. THE THREAT OF INTRODUCED DISEASES T. R. Peace Formerly Chief Research Officer (Deceased), Forestry Commis- sion, Forest Research Station, Wrecclesham, Farnham, Surrey, England Relatively few fungi, bacteria, and viruses attacking forest trees have a worldwide distribution, or even cover all the areas where avail- ability of host and suitability of climate would permit their develop- ment. Many instances are already known, however, where pathogens have spread from one continent to another, and there are alarming pos- sibilities of further spread. This paper attempts to discuss the risk, and how its immediate and long-term effects can be lessened. Discus- sion is limited to diseases caused by fungi, bacteria, and viruses, but similar principles apply to insect pests. On land masses where the host tree or trees have a continuous dis- tribution, spread of diseases by natural means is almost inevitable and extremely hard to stop. But where there are breaks in host distribu- tion, for instance a mountain range or a desert, and particularly where there is a sea barrier, natural dissemination becomes much less impor- tant or even nonexistent, and man is the chief agent of spread (Orton and Beattie 1923). Thus intercontinental transmission of disease, except between Europe and Asia, is almost entirely due to man’s agency. This paper is divided into two main sections. In the first and smaller, the risk is considered briefly. In the second, various actions, which have already been taken or can be taken in the future, are con- sidered. The second part may perhaps be regarded as outside the proper purpose of the paper I was asked to submit. If so, I must apologize to Professor Boyce on whose ground I will have trespassed. Nevertheless it may be valuable if we have these actions in mind when we are considering individual diseases. In any case, this is a matter in which I have some experience and rather definite views. This leads me to welcome an opportunity of putting them before the Group. The Problem A study of the present known distribution—both in the positive sense of areas known to be infected and in the negative one of areas known to be uninfected—makes it clear that many pathogens already known to be dangerous are not yet generally present throughout their host’s geographical range. In particular, they may not yet have pene- trated all the areas where the host species has been planted as an ex- otic. Bacterial canker of poplar, whether it is caused by Pseudomonas syringae or Aplanobacterium populi, is still apparently confined to Europe; Phloem necrosis, a virus disease of elm, to North America: the fungus Monochaetia unicornis, causing canker on cypresses, to Africa and New Zealand; and Ceratocystis fagacearum, the cause of oak wilt, to North America. The compilation of any list of dangerous 33 34 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 pathogens of incomplete distribution indicates clearly that the incom- pleteness rests partly on lack of knowledge. A recent unpublished list of forest diseases considered potentially dangerous in Britain was based on reasonably certain information that the diseases listed were not present in this country, but that they were present in other areas. Most records were from North America and Europe, where forest pathological investigations have been reason- ably thorough. The tabulation below, based on this list, shows the number of diseases, absent from Britain but considered potentially dangerous to British forest trees, recorded from the different continents : Country Number North’ America only. 22027 elie seen ae ae BO pe Only te 2a Eee Ee ie eee ee eae TSE CO) Uy eam el ted AIA alg lod AAU on North America and Hiro pes. 202-222 ee eee INorthvA merica and Asia. 6. fog ee eee ee North Ameri¢a, Asta, dnd ‘Huxope: 2" 32 oe ee North and South -Auericas 22 73.02 eee North and South America and Europe__________-___- North and South America, Europe, and Asia_____-_- Ritrope and Asia 2 ee A trica, and New Zealand coe eee ee The preponderance of North American entries in this list is partly due to the importance of North American conifers in British forestry. The relatively small number of dangerous European diseases, not present in Britain, is partly the result of its proximity to the rest of Europe, so that many diseases have already achieved a common distri- bution. The low numbers for other continents are mainly due to the relatively small importance of their trees in Britain and _to the fact that in some cases large areas lie in entirely different climatic zones from Britain. Nevertheless, it is almost certain that the low figures for Asia, where nearly all the dangerous diseases listed are Japanese records, and for other continents poorly represented in the list, are also partly due to lack of knowledge of the pathogens occurring there. While any list of known dangerous pathogens with incomplete con- tinenta] distributions is certainly impressive, particularly in the number of species involved, it is certain that more diseases remain to be discovered when pathologically unexplored regions, stich as China or most of the temperate area of South America, are properly investigated. Thus, we are faced with a large number of diseases known to be damaging in the countries where they are present and therefore presumed to be damaging in other countries to which they might spread. There is the strong possibility that other diseases, not serious in their present range, might prove dangerous if transported to other areas, either more favorable to their activities or less favorable to their host tree. Finally, there are almost certainly parasites, as yet un- recorded, that will attract attention only when the countries where they now exist are pathologically explored, or when they reach other countries. Thus, we must consider what immediate steps can_be taken to prevent or slowup disease spread from place to place, and what iN S) Meee bd DOH or 9 00 DANGEROUS INTERNATIONAL FOREST TREE DISEASES 35 long-term work can be undertaken to mitigate the effects of such diseases should they eventually reach other countries or other con- tinents. Partial Solutions Phytosanitary Action Phytosanitary action can be taken in a number of ways. General reviews of these have been made by Giissow (1936), McCubbin (1946, 1954), and Soraci (1957). The means used fall roughly into three categories: (a) measures taken in the exporting country, (b) measures taken in the importing country, and (c) embargoes, whereby carriage of specified plants or parts of plants from one country to another is completely forbidden. As far as trees are concerned, there are three main types of material on which fungi, bacteria, and viruses are likely to be transported, namely seed, plants, and timber. Seeds present the smallest risk. A1- though a good case can be made for the routine treatment of many agricultural seeds, there is so little evidence of disease transmission on tree seeds that no general action can be justified. Only in the case of chestnut blight, Xndothia parasitica, on Castanea. seed is there a strong case for seed disinfection. Timber is much more dangerous, especially when it is unbarked. Ceratocystis ulmi, the cause of elm disease, was taken from Europe to North America on unbarked timber, and Endothia parasitica may have reached Europe from North America in the same way. There has been a very general tendency, except in the case of fruit and vegetables, to neglect the risk involved in the movement of final products, partly no doubt because restrictions on them would almost invariably involve serious restrictions on trade. Yet transmission of some pathogens, such as L'ndothia parasitica on Castanea and on Quercus, or Hypoxylon pruimatum on poplar, is much more probable on timber than on small plants. Morgan and Byrne (1957) have recently stressed the dangers inherent in the uncontrolled movements of timber from country to country or from continent to continent. There are of course several well-known examples of the transmis- sion of tree diseases on young plants. The most notable is the importa- tion on nursery plants of Cronartium ribicola, the cause of white pine blister rust, into North America from Europe. Most of the quarantine regulations designed to prevent the entry of tree diseases have referred to living plants, rather than to seed or timber. Although embargoes obviously give the best chances of success, there is rather general objection to their use. Where trade exists they are bound to be restrictive, and there is always the possibility that they may be applied for economic rather than phytosanitary purposes. A complete embargo on seed would obviously impose too severe a restric- tion on any country which was largely dependent on exotic trees. A complete embargo on young trees and parts of trees would stop the international distribution of trees such as poplars, which are normally raised as vegetatively propagated clones and of grafting material of selected trees for breeding work. A complete embargo on timber would only be possible for a country that possessed a suf- ficiency of all kinds of timber for its own use. Conditions vary in different countries and, therefore, so does the extent to which they 36 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 are able to apply embargoes, undeniably the most effective phytosani- tary measures. In practice, embargoes can hardly be made complete. Limited importation by licenses subject to specified precautions must be granted for scientific purposes. In any case spores may enter on aircraft, and passengers may carry diseased material knowingly or unknowingly in their baggage (Sherman 1957). It is generally admitted that inspection of imported material on arrival is a very unreliable way of preventing the entry of diseases (Gravatt and Parker 1949; Gram 1955). In the case of large con- signments only a sample can be inspected and, unless the incidence of disease is very high, it may well go undetected. In some cases the disease may be in a stage which is not detectable even by careful visual inspection. For instance, Chrysomyxa rhododendri was im- ported into the United States as mycelium in azalea leaves. By the time fructifications appeared and the disease became detectable, the plants had been widely distributed (Gould, Eglitis, and Doughty 1955). In fact, inspection on entry, except for the occasional detection of very badly diseased consignments or of material subject to embargo, is valuable mainly in encouraging better phytosanitary practices in the exporting country. There is obviously a better chance of achieving satisfactory inspec- tion in the country of origin. If plant inspection is started in the nursery, it can be extended over a period of time and carried out with a knowledge of some of the possibilities of infection to which the crop is subject. Even then it is impossible to state honestly that the plant material is entirely free of all disease. There is no doubt, however, that efficient preexport inspection, especially in the nursery, can greatly lessen the risk so that the danger of importing from any particular country depends not only on the pathogens present there, but on the efficiency of its phytopathological inspection service. Every country is therefore in a position to lessen the chances of disease transmission by improvements in the scope and skill of its inspection service and by the encouragement of phytosanitary practices among its exporting nurserymen. The principles underlying plant quarantine regulations have been discussed by Moore (1952, 1955) and by Soraci (1957). There is a strong tendency to base regulations on our present knowledge of spe- cific diseases, in particular on their potential danger and on their distribution, and to condemn widespread embargoes on the ground that they are based on unreasonable fears of the unknown, However, we must remember our almost complete lack of knowledge of potential tree pathogens in some of the phytopathologically less advanced coun- tries. It is also necessary to take into account the obvious possibility that a known pathogen may behave quite differently when moved to a new environment. The behavior of Phaeocryptopus gaumannii on Pseudotsuga and Keithia thujina on Thaja, when moved from North America to Europe, are frightening examples; however, the increased importance of Hezthia is due mainly to its severe attacks on nursery plants of 7huja in Europe, as compared with its behavior on natural regeneration in North America. Even when a fungus is already widespread, there is a danger that it may have regional strains of differing virulence, the transfer of which could prove damaging. This may well be the case with Lophodermium pinastri, the needlecast of pines. Such considerations may support the | | DANGEROUS INTERNATIONAL FOREST TREE DISEASES 37 application of embargoes where they can be imposed without damage to the forest economy. In the author’s opinion, the embargo should always be considered when phytosanitary measures are being devised, and only dismissed on very strong reasons against its use. It is outside the scope of this paper to discuss al] the quarantine measures which have been imposed by various countries against tree diseases. They have been fully summarized in an F.A.O. publication by Ling (1952 and after). The United States regulations, with a very long list of tree genera and species, and with some restrictions applying only to specified regions, represent a painstaking effort to relate quar- antine measures to the existence and distribution of known diseases. The British regulations, as far as conifers are concerned, provide an example of the widespread embargo designed to protect a group of genera from all pathogens known or unknown from all regions. In any case, of course, phytosanitary measures can only postpone the more or less inevitable spread of all diseases to all areas where there are susceptible crops for them to attack. Nevertheless such a postponement may have enormous value in giving time for resistant strains to be discovered or developed, and for control measures to be elaborated. The remaining sections of this paper indicate what can be done dur- ing this “period of grace” to ensure that we are equipped to meet the forest pathological problems of the future when transport will be so rapid and so cheap that restrictions on movements of goods will be completely out of place. Exploratory Action When we consider tropical forests, it is readily apparent that the area which is relatively unexplored from the disease point of view is very large. For many extensive regions incomplete lists of fungi do exist; but rarely, except in the more highly developed countries, have the listed fungi been evaluated phytopathologically. Thus, we have little idea how much damage they are doing in their native country and no information at all on which to base estimates of their behavior if they were moved to other countries or continents. Obviously, there- fore, there is a great need for what might be called “phytopathologi- cal exploration,” not only in many tropical forests, but also in quite large areas in the temperate regions. It is clearly important that such work should be done thoroughly and critically. First, an important disease may exist outside the forest proper on scattered trees or in scrub areas, so that surveys cannot be limited to areas of utilizable forest. Second, diseases may be of slight importance in their country of origin because the native host trees are either resistant, as was the case with L'ndothia parasitica on Castanea in Asia (Beattie and Dil- ler 1954), or of restricted distribution. Clearly it is difficult, and in the case of tropical forests impossible, to assess the risk exactly or to consider general precautionary meas- ures until we have a much more widespread knowledge of tree dis- eases. Unfortunately, while short-term visits such as collecting ex- peditions may provide valuable information on the occurrence of path- ogens, evaluation of these pathogens requires study over a period of time and must therefore await the development of a forest pathologi- cal organization in the region concerned. 38 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Research Action Any advance in our knowledge of tree diseases is naturally of value when we come to consider the possibilities and results of their trans- mission from one area to another. The testing of the trees of one country or continent for their resistance or susceptibility to the dis- ease of another, whether by chance exposure, deliberate exposure, or inoculation, is particularly valuable. In many countries there is so much information already available, but not necessarily collected, from existing plantations of exotics that it is doubtful if plantings de- signed merely for disease recording purposes can be justified. These test plantings are really only useful when placed in regions where the pathogen population is unexplored. The possibility of doing this is, of course, usually limited by the lack of pathologists in those regions. It may therefore prove easier to observe the development of diseases in carefully sited plantations, rather than over the unexplored area as a whole. In addition, forest plantings of exotics are probably lacking in a rel- atively undeveloped country, so that stands specially formed for path- ological study may provide the only chance of getting data on the sus- ceptibility of nonnative trees to the local pathogens. Provided the limitations imposed by siting in relation to virtually unknown sources of disease and by the limited number of plantations are taken into con- sideration, there is no doubt that such special plantations could yield results of very definite international value. In pathologically explored regions, plantations designed to test under natural conditions the reactions to specific diseases and there- fore deliberately placed in regions of high infectivity would be more valuable, and there is certainly room for their extension. It is also desirable to extend inoculation tests in one country on tree species of importance to another (Gravatt and Parker 1949; Riker 1957). With any of these methods, care must be used in the interpreta- tion of results. The presence ‘of a disease ia a plantation is always more significant than its absence; very good evidence is required before the absence of a disease from a tree can be taken by itself as proof of immunity or resistance. Even when disease is present, care must be exercised, for unequal distribution of sources of infection may cause unequal distribution of damage, which thus may have no relation to the inherent susceptibility and resistance of the trees affected. For this reason, information from a large number of exotic plantations, preferably growing under a wide range of infective and climatic conditions, is likely, if intelligently interpreted, to be of more value than that collected from a limited number of specially designed test plantations. None of the methods mentioned above will eliminate the effect on diseases of differences in climate and other environmental factors between one country and another. For this reason, the disease reac- tions of a tree species in one place cannot be taken as a certain indica- tion of its behavior towards the same pathogen elsewhere. They do, however, give the best information which can be procured without actually moving the pathogen, a method which naturally is completely inadmissible. There is danger even in moving cultures of pathogens from one country to another (Wheeler 1957). Transfer of cultures can be justi- fied only if it serves some useful purpose and provided the cultures _-~-. DANGEROUS INTERNATIONAL FOREST TREE DISEASES 39 are carefully guarded. The use of an exotic pathogen, or even of an exotic strain of a native pathogen, for inoculation purposes is a patho- logical crime of grave significance. There is also room for research on the means of transmission of tree diseases over long distances, though this is of less permanent value than work on disease behavior. Too little is known about the relative importance of different means of transmission. In particular it would be valuable to have more evidence on the importance of seed as a means of transmission. Evaluatory Action Any increase of knowledge of the distribution of diseases and of their behavior on different hosts in different climates is of great as- sistance in evaluating their importance, both present and potential. If more facts were available on the actual and potential economic losses inflicted by diseases transported from one area to another, there would be more reasoned support for expenditure, either on means to prevent their spread or on the mitigation of damage once they had done so. In the past there has been a tendency to behave as 1f all damaging diseases were of equal importance, at any rate as far as restrictions of spread is concerned. It might be better if our energies were concentrated on the restriction of a limited num- ber of diseases, leaving others to spread more or less unhampered, either because they were easily controlled or avoided, or because there was good evidence that they would not be seriously damaging. How- ever, selective action of this kind would be possible only on the basis of much greater knowledge of disease behavior than we yet possess for most forest pathogens. It can therefore only be practiced when much more work has been done on what might be termed “interna- tional disease behavior.” Practical Possibilities It is apparent from what has been said above that the amount of work required to build up a knowledge of disease behavior, suffi- cient to form a basis for international action is very great indeed. The limitations on this work are primarily those of staff. At first sight the most important limitation is the absence of forest patholo- gists in many countries, but the very small number in most other countries, particularly European countries, is equally serious. In many cases, the workers are so few that their energies must inevi- tably largely be devoted to immediate forest pathological problems. They have little time to spare for investigations which are not of im- mediate practical value or which are designed with long-term inter- national, rather than immediate national, ends in view. Most govern- ments take the view that forestry, earning as it does low rates of interest, cannot support a high expenditure on research. And thus they expect any substantial increases in research expenditure to be clearly linked with resultant economic advantages. Economic ap- praisals of disease losses, and in particular of the relation of research costs to the prevention or mitigation of these losses, are thus obviously desirable. Only thus can a reasoned case be stated for increased ex- penditure on pathological research. _In the meantime, any schemes for international cooperation must either take full account of the limitations which the preoccupation of . forest pathologists with their local problems imposes, or else allow 40 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 money for the appointment of special staff to carry out the work en- visaged. In the field of international cooperation, it is perilously easy to envisage grandiose schemes, the initiation, let alone the oper- ation, of which is far beyond the means available. Of course the full- est possible international use should be made of work already in progress, but even the coordination of this involves considerations of time and money, which cannot be overlooked. Thus, while few would deny the importance of increasing our knowledge of diseases, of the damage which they are likely to do if they become more widespread, and of the means by which this damage can be avoided, it is vital that the international work involved should be provided with a sound economic background, thus justifying the substantial expenditure involved. Literature Cited Beattie, R. K., and Diller, J. D. Fifty years of chestnut blight in America. Jour. Forestry 52 : 323-329. 1954. Gould, C. J., Eglitis, M., and Doughty, C. C. European rhododendron rust (Chrysomyxa ledi var. rhododendri) in the United States. Plant Dis. Rptr. 39 : 781-782. 1955. Gram, E. Barriers and by-passes in plant trade. Ann. Appl. Biol. 42: 76-81. 1955. Gravatt, G. F., and Parker, D. E. Introduced tree diseases and insects. U.S. Dept. Agr. Yearb. Agr. 1949: 446-451. R.A.M., p. 625. 1949. Giissow, H. T. Plant quarantine legislation—a review and a reform. Phyto- pathology 26: 465-482. 1936. Ling, L. Digest of plant quarantine regulations, F.A.O. Rome. 164 pp. and subsequent supplements. 1952. McCubbin, W. A. Preventing plant disease introduction. Bot. Rev. 12: 101-139. 1946. R.A.M., p. 320. 1946. The plant quarantine problem: A general review of the biological, legal, administrative and public relations of plant quarantine with special refer- ence to the United States situation. Chronica Botanica Co., 255 pp. 1954. Moore, W. C. Principles underlying plant import and export regulations. Plant Path. 1: 15-17. 1952. The development of international co-operation in crop protection. Ann. Appl. Biol. 42: 67-72. 1955. Morgan, F. D., and Byrne, J. The desirability of international quarantine meas- ures for exports and imports of timber and timber products. Brit. Comm. Forestry Conf., 7 pp. 1957. Orton, W. A., and Beattie, R. K. The biological basis of foreign plant quaran- tines. Phytopathology 13: 295-306. 1923. Riker, A. J. The discovery of important diseases before they move from one country to another. Phytopathology 47: 388-389. 1957. Sherman, R. W. Co-operation of world tourists sought in plant quarantine en- forcement. FAO Plant Protect. Bul. 5: 89-90. 1957. Soraci, F. A. Redefinition of the principles of plant quarantine and their rela- tion to the current problems. Phytopathology 47: 381-382. 1957. Wheeler, W. H. The movement of plant pathogens. Phytopathology 47 : 386-388. 1957. ee eee eet eimai EXAMPLES OF WIDELY DISTRIBUTED FOREST DISEASES J. R. HansprovucH Director, Division of Forest Disease Research, Forest Service, US. Department of Agriculture, Washington 25, D.C., USA. In our review of selected dangerous forest diseases in Asia, Europe, and North America, our primary objective is to call attention to a few diseases whose importance in these continents illustrates their potential damaging capacity if they should be introduced to other continents. Most of them are presently restricted to one continent but we have included a few that have already become well-established abroad. In all cases, however, precautions are recommended to pre- vent or limit further spread to additional continents. There are many destructive forest diseases already widely dis- tributed. This does not mean that further efforts are unnecessary to restrict the spread of the pathogens that cause them. Many fungi have two or more races, sometimes varying in pathogenicity. For example, Puccinia graminis Pers., the cause of stem rust of cereals and grasses, has been differentiated into at least six distinct varieties in North America, varying in spore size and the kinds of plants that they attack. Within these recognizable varieties there are races that may be indistinguishable by morphological characteristics but differing markedly in pathogenicity. There is nothing to preclude the existence or the development of similar races within species of destructive forest fungi. For that reason, measures to prevent fur- ther spread of widely distributed forest diseases are important. The following forest diseases are known to occur on two or more continents. The list is not exhaustive but includes many well-known, widely distributed forest pathogens. The tabulation uses the follow- ing abbreviations: Af., Africa; As., Asia; Aus., Australia or New Zealand; E., Europe; NA, North America; SA, South America; W, Worldwide. The pathogens and their distribution are: Distribution Pathogen by Continents Agrobacterium tumefaciens (Sm. & Town.) Conn __________ w mmiars melca (Vahi.)) Quel... Ww Ceratocystis ulmi (Buism.) Moreau____..—-_________.____- As., E., NA DEIR ET EPS go ed ee Se ee Af., Aus., E., NA UNUAEMRRMINUS “WEUVSEOHLIE (TAEDA As., E., NA lene. amen. ( Des.) Wicks. 2 2 w Dothichiza populea Sacc. & Briard_______________________ B., NA, SA Endothia parasitica (Murr.) Ander______--______________. As., E., NA EB A LS Bh Oh) 5 a ee As.,E., NA ES es a eee eee As., E., NA Fusicladium saliciperdum (All. & Tub.) Tub______________ E., NA Lophodermium pinastri (Fr.) Chev__._._._______.__._____.___. As., Aus., E., NA Phaeocryptopus gaumanni (Rhode) Petr__________________ B., NA Tawysciospora miyabena Wak... As., E., NA Phytophthora cinnamomi Rands_______--_____--_________ £ As., Aus., NA Rhabdocline pseudotsugae Syd___________________________ E., NA LEE ES Eg OE ge a ee ee As., E., NA Verticillium albo-atrum Rein. & Bert_____________________ Af., Aus., E., NA 41 SELECTED DANGEROUS FOREST DISEASES IN ASIA, EUROPE, AND NORTH AMERICA Summary by Host and Continent The following tabulation summarizes dangerous pathogens by host and distribution. Abbreviations used are: Eur., Europe; N.A., North America; S.A., South America. Host, family, and genus Pathogen Symptoms Continents Acanthaceae: Ruellia_ Cronartium flaccidum___--- Leaf rust__ Asia, Eur. Aceraceae: AC ET As 2 LIE TLE aa. Helicobasidium mompa._-- Rootrot__ Asia Strumella coryneoidea___-_-- Canker____ N.A. Anacardaceae: Rhus__ Helicobasidium mompa_._-- Root rot-_ Asia Asclepiadaceae: ASELE DIMS ee eae Cronartium flaccidum__-_- - Leaf rust__ Asia, Eur. Cynanchum_-_-_-_---- Preah 18 5 fo Wek sarameess SI LA et Bite de FTG (0 yicihes Do. Balsaminaceae: -Impasi; 2° dois.) 2 eee Fut dow Do. tiens. Betulaceae: (O EAT Tied Ei Bis snl lls Clitocybe tabescens_-__-_-_-_-- Root rot__ N.A. Strumella coryneoidea___-_-- Canker____ Do. Bignoniaceae: Catalina esa Helicobasidium mompa__-- Rootrot___ Asia CTNGB SUS px eo ee (oo Wie tae mG She eMC S 4 Gn ie SRE do. Do. Casuarinaceae: Castarina= WLOit we Chilocybe- tabescens i sn Cream Gow MAING Trichosporium vesiculosum_ Wilt__---- Asia Cornaceae: Copnusecc ace a Clitocybe tabescens____---- Rootrot.._. N.A. INS Stee hat es ee Strumella coryneoidea____-- Canker 222 Do. Cupressaceae: Calltixis a8 seas Fe. Cutocybe tabescens_____-_-_- Root rot___ Do. CRamMGeCYUNaTise 408 Le ie MO eic B lo Mee One, Do Helicobasidium mompa___- ----- do__. Asia Phomopsis juniperovora____ Needle N.A. blight. Porta werritas 2 oe ee Root rot__-_ Do. Cipressuse oo: eee Clitocybetabescens 2. - > = edenee Do. Phomopsis juniperovora____ Needle Do. blight. TUNE NET ALS rane a eS Clitocybe tabescens____-__-- Root rot_-_ Do. Phomopsis juniperovora____ Needle Do. blight. Phymatotrichum omni- Rootrot__- Do. vorum LB Tiss epee a See Pe, Clitocybe tabescens_______- Sh IO SEE Do. Helicobasidtum mompa2] => 22 dol ==) Asia. Keithia thujynas=- 4222 Needle Kur., N.A. blight Phomopsis juniperovora._... ----do._-- N.A. Phymatotrichum omnivorum Root rot-- Do. Dipterocarpaceae: Shorea. ee ae Fomes.caryophyli_.. 2. 2-8 dole aa WAsia- Hypoxylon mediterraneum_._ Canker__-_- Do. Polyporus shorea__.._----- Heart rot_- Do. Ebenaceae: Diospyros. 8. ek ae Cephalosporium diospyri._. Wilt _-_---- N.A. Phymatotrichum omnivorum. Root rot-- Do. 42 DANGEROUS INTERNATIONAL FOREST TREE DISEASES Host, family, and genus Pathogen Eleagnaceae: | eerie i ales Phymatotrichum omnivorum- Ericaceae: Arctostaphylos_____- Chrysomyza arctostaphyli_ Fagaceae: OES Ss Ceratocystis fagacearum___-_ Cronartium fusiforme____-- Deere 2 Soo Helicobasidium mompa- --- Pseudomonas castaneae___- Strumella coryneoidea____-_- Castanopsts___----- Ceratocystis fagacearum___- Cronartium fusiforme___-_-- 2 ee Strumella coryneoidea____-- Inthocarpus__------ Ceratocystis fagacearum__-- Cronartium fusiforme__-__-- foe hs ee el alee Ceratocystis fagacearum_.--- Clitocybe tabescens_____--_- Cronartium fusiforme__-_-_-- Coquercaamir Ae Helicobasidium mompa__-- Strumella coryneoidea__-__-- Gentianaceae: | Cronartium flaccidum____-- Ginkoaceae: nS ee Helicobasidium mompa_ _--- Hamamelidaceae: Liquidambar ___---- Clitocybe tabescens___-_-_-_- Hippocastanaceae: i LT i ae Guignardia aesculi_____-_-_- J uglandaceae: ep ee Clitocybe tabescens___-_-_--- Strumella coryneoidea____-- OS ek Helicobasidium mom a ae Phymatotrichum omnivorum- Piniycarya__.-.- =. Helicobasidium mompa_ - -- Leguminosae: ot En Clitocybe tabescens_-__-_---- hoes ares Glomerella acaciae________- i Clitocybe tabescens____--_-- CT Phymatotrichum omnivorum. SOT ee Helicobasidium mompa__-- LS |) Fusarium solant__-------- eS Chlorogenus robiniae___-_-_- Phymatotrichum omnivorum_- Gymnocladus___-_-_-_- 2 Se Ea ect mca erate Scie oT) ia. Chlorogenus robiniae__-___- Helicobasidium mompa__-- Phymatotrichum omnivorum- Liliaceae: oS See Melampsora allii-populina_- Loascaceae: Grammatocarpus____ Cronartium flaccidum______ rene a eg Se ees 8 pe ee oe Magnoliaceae: Iirtodendron____-_-_- Helicobasidium mompa_ --- Moraceae: Broussonetia_______ See ee _ ee a Clitocybe tabescens_______- Helicobasidium mompa___- emis Tt Phymatotrichum omnivorum __ Sake Helicobasidium mompa__--_- Phymatotrichum omnivorum Myrtaceae: Eucalyptus_________ Clitocybe tabescens_______- Oleaceae: a Pseudomonas frazini__-_--_- Phymatotrichum omnivorum 687-137 O—63———4 Symptoms Root rot__ Leaf rust__ Leaf rust__ ees Sere Root rot__ Blight_____ Canker_ as Root rot__ Leaf rust__ Root rot__ Canker____ Leaf rust__ Root rot__ Leaf blotch Root rot_ _ Canker____ Root rot__ Heart rot__ Anthracnose. Root rot_ _ Leaf rust__ es at ahs 5 Root rot __ 5 Ae |") ee ae: Canker___-_ Root rot__ 43 Continents N.A. Asia. N.A. Asia, Eur. Asia. N.A. Eur. Do. 44 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Host, family, and genus Pathogen Symptoms Continents Pinaceae: CAND UE Sete aes he een ae Arceuthobium campylo- Witches’- N.A. podum. broom. Phomopsis pseudotsugae__. Canker____ Eur. ROLVOWEULIEs sae ee eee Root rot__ N.A., Asia Rehmiellopsis balsameae__._ Needle N.A. blight. Cedrisn 2ae see eae Clytocybe tabescens_______- Root rot__- Do. Reridermium:. cedris so s48 Witches’- Asia broom. COT IL Me eo ee Dasyscypha willkommii_... Canker____ Eur. Helicobasidium mompa__.- Root rot_. Asia Mycosphaerella larici-lepto- Needle . Do. lepis. cast. Physalospora laricina_-__--- Shoot Do. blight. POT 1G WELT yaaa ee eee Root rot... N-.A. YAY DT) te ieee ines Ta EN Arceuthobium pusillum__.. Witches’- Do. broom. Chrysomyzxa arctostaphyli__ __--- doz2== Do. @. deformans 2 ei ae Needle Asia rust. Helicobasidium mompa___. Root rot_-_ oO. PP OTT ADEUP Ue down s2 Asia, N.A. Scleroderris lagerbergit___-- Canker____ Eur. 1 4 TCL Se Cae Rear Arceuthobium americanum. Witches’- N.A. broom. A. campylopodum___------ ie Oe eess Do. Atropellis pintphila__-_-_--- Canker____ Do. Cenangium ferruginosum_.._ Dieback_.._ Eur. Cercospora pini-densiflorae. Needle Asia blight. Clitocybe tabescens__.__-_.. Rootrot._ N.A. Cronartium comandrae_.___- Canker___-_ Do. C: flaccid yee 2 do_.-2 “aur; vAsia CST ONIN ea = eee ae ere. Os. 4 RN eAY Cuhimalayense 224 22=-002222 JAgial Cquerciiim= == ee ee Galle2 ee: N.A. Elytroderma deformans__-- Needle cast Do. Helicobasidium mompa__-- Root rot-- Asia Hypoderma lethale_____-_- Needle N.A. cast. Hypodermella sulcigena____ ----do__-- Eur. Melampsora pinitorqua_._._. Canker_...__ Eur., N.A. Peridermium harknessti_.__.. Gall_-__-- N.A. Fe stalactufornmes. = Canker___- Do. Phacidium tnfestans___-- ~~ Needle Asia, Eur., blight. N.A. Phomopsis pseudotsugae__._ Canker____ Eur. Phymatotrichum omnivorum Rootrot___ N.A. TROTVG LICL ase ee ee s2008 525 Do. Scirmhiia acicolas 4) —- Needle Do blight. Scleroderris lagerbergit_---- Canker____ Eur. Pseudotsuga__------ Arceuthobium douglasit__-. Witches’- N. AG, broom. Phomopsis pseudotsugae__. Canker____ Eur. POTUO UCU Root rot__ N.A. Sequotd-2-. 252-52 Phomopsis pseudotsugae__._ Canker_--_ Eur. TSUGae se eae Arceuthobium campylo- Witches’- NSA podum. broom. Phomopsis pseudotsugae__. Canker____ Eur. ZOTAG, WEL ee Root rot_. Asia, N.A. Platanaceae: FLA nee tce ee Ceratocystis fimbriata___--- Canker____ N.A. Helicobasidium mompa_...- Root rot__ Asia. Phymatotrichum omni- RO (o eRe N.A. vorum. —_ Lee DANGEROUS INTERNATIONAL FOREST Host, family, and genus Pathogen Ranunculaceae: [a Cronartium flaccidum___-_-- Rosaceae: Cratacgts. 2... = Clitocybe tabescens_____-~-- SE a a SOR 2S) oe ee ee ees Helicobasidium mompa_ -_-- A ae Se Clitocybe tabescens____--_- Helicobasidium mompa__-- Phymatotrichum omnivorum emrmesires, Sy 8 st es Clitocybe tabescens___-_-_-_-- Salicaceae: ET Sp ec Chrondoplea populea_ _ _--- Helicobasidium mompa_ --- Hypozylon pruinatum _ -_--- Melampsora allit-populina_ Do selor quale <= =k ts Phymatotrichum omnivorum Septoria musiva____-_---- Septotinia populiperda___-- Venturia populina__-_-_---- We tropa se bh Se ae Deere ek Se oo Helicobasidium mompa_ _-- Santalaceae: Comandra._. _._-__ Cronartium comandrae___-- pamanm: <2. 2) _ 22 Sandal waruag ns 8 22 eo = 2 Sapindaceae: LE tee Phymatotrichum omni- vorum. Scrophulariaceae: LS Peridermium harknessit____ P stalaciijerme_. 2 | | i Cronartium flaccidum___-_-- Melampyrum___-_-__- Sea eS Se ye Py fe) Peridermium stalactiforme__ Le ae Cronartium flaccidum___-_-_- Paulownia________- Paulownia virlis_ = ___- = . Pedicularis________- Cronartium flaccidum____-_- Simarubaceae: LS Phymatotrichum omni- vorum. Solanaceae: Schizanthus_____-_-- Cronartium flaccidum__---- Tamaricaceae: TEST es Phymatotrichum omni- vorum. Taxodiaceae: Cryptomeria_______- Cercospora cryptomeriae___- Helicobasidium mompa- _-_- a Cercospora cryptomeriae__-_- Tiliaceae: LL Strumella coryneoidea_____- Tropaeolaceae: Tropaeolum________ Cronartium flaccidum____-- maceae 5 5s lapel agentes Helicobasidium mompa _ _-- Phymatotrichum omnivorum oo ee Helicobasidium mompa -_ _-- Lf | en Phymatotrichum omnivorum Verbenaceae: oo ae Olivea tectonae__________-- Wermene oo Cronartium flaccidum_____- TREE DISEASES Symptoms Leaf rust__ Root rot__ _ at ga ses en we Ne | CeCe" eee ee a Canker___-_ Root rot__ Canker____ Leaf rust__ Sa | ee Root rot__ Canker____ Leaf blotch Leaf spot__ SAS ae Root rot__ Leaf rust__ Spike disease. Root rot___ Leaf rust__ Leaf rust__ Root rot___ Leaf rust__ Root rot___ Canker____ Root rot__ Canker___-_ IPae: CLINE Leaf rust__ Root rot_-_ Virus wilt_ Root rot _-_ Leaf rust__ ea ee 45 Continents Eur., Asia. N.A. Do. Asia N.A Asia N.A. Do. Eur., N.A.., S.A. Asia N.A. Eur. Eur., N.A N.A. N.A., S.A. Asia, Eur., Eur. i Do. Asia N.A. Asia. N.A. Do. Do. Eur., Asia. Do. N.A Eur., Asia. Asia Eur., Asia N.A Eur., Asia N.A Asia Do. Do. N.A. Eur., Asia Asia N.A Asia N.A. Do. Asia Eur., Asia DANGEROUS FOREST DISEASES IN JAPAN Rokuya IMaAzEKI Director, Division of Forest Protection, Government Forest Experiment Station, Meguro, Tokyo, Japan, and Kazuo Ito Chief, Section of Forest Pathology, Division of Forest Protection, Government Forest Experiment Station, Tokyo, Japan Witches’-Broom of Paulownia Virus (no specific name). In the case of normal paulownia, a bud sprouts in spring and grows to a new stem or a new branch, which bears about 10 pairs of opposite leaves. Stem growth ceases before the beginning of September. The axillary buds of the new stem or the branch do not sprout for this season, so that they usually have no lateral shoots for the current season. In the diseased paulownia, on the contrary, a bud sprouts in spring and grows to a new stem or to a new branch which does not cease its growth until late in autumn and the primary axillary buds sprout immediately. The sprouting of the axillary buds and the growth of the shoots and branches without any restriction are the causes of the symptom of the witches’-broom. The branches and shoots of the diseased tree are slender and brittle and show an extreme negative geotropism. The color of diseased branches and shoots becomes yellowish green. There are two sorts of leaf-forms in healthy paulownia. The one is the leaf-form seen in young trees 1 or 2 years old and the other is that seen in older trees. The former show both large and small in- cisions. With the growth of the tree, the leaves which have only large incisions increase in number, and within 2 or 3 years the whole tree comes to have leaves with large incisions on the margin. In the diseased tree, however, the leaves with both large and small incisions appear even though it becomes more than 2 years old. Usually all the leaves on the diseased shoots are abnormally thin and narrow, and are uneven on the surface. Their color is yellowish. Malformed leaves are often observed on the diseased shoots. This is the most serious disease of paulownia trees in Japan, and causes severe damage in many plantations in the central and southern parts of this country. Heavily infected trees are stunted and killed. Insect transmission of this disease is not known. Intercontinental spread is possible through shipment of infected trees or rootings. Importation of living plant material other than pollen or seed should be forbidden. Distribution: In Japan it is common from the central to southern part and scattered in the northern parts except Hokkaido. Also found in China; Korea(?). 46 DANGEROUS INTERNATIONAL FOREST TREE DISEASES 47 Hosts: Scrophulariaceae— Paulownia tomentosa, P. fortunei, P. kawakamit. Literature: Tokushige, Y. Witches’ broom of Paulownia tomentosa L. Jour. Fac. Agr., Kyushu Univ. 10: 45-67. 1951. Witches’ broom of Paulownia tomentosa L. On the occur- rence of the witches’ broom affected trees in paulownia forest (Japanese with English resume). Jour. Jap. Forest Soc. 34: 4-7, 1952. Bacterial Blight of Chestnut Pseudomonas castaneae (Kawamura) Savulescu. The disease is most conspicuous in buds and young shoots but also occurs on the leaves. veins, petioles, and bracteal leaves, the last being usually at- tacked first. The sign of the disease in the early stage is water-soaked spots on the leaves and young shoots in which the cortical parenchyma is destroyed, forming bacterial cavities and resulting in brown cracks. Leaves attacked when young become distorted and leaves of infected buds shrivel and die. White and yellow bacteria are isolated from the diseased lesions, of which the former is pathogenic to chestnut and found associated with the latter. A short rod, 1.0-1.84 X 0.8-1.2u, motile, with one to five polar flagella; singly or in pairs, no spores, no capsules, Gram-negative, facultative anaerobic, beef agar colonies white, round, slightly undu- late and viscid, bouillon clouds without pellicle; potato decoction agar colonies white, radiately rugose, gelatin not liquefied, diastatic action absent, milk peptonized without coagulation, indo] and hydrogen sul- phide not produced, nitrate and methylene blue reduced, acid from dextrose, saccharose and glycerine without gas, neither acid nor gas produced from lactose, no gas from maltose and potassium. The distribution of this bacterium is limited to the southern districts of Japan. Intercontinental spread may be possible only by infected living trees, though pollen dissemination is also possible. Range: Japan-Kyushu and Chugoku Districts. Host: Fagaceae—Castanea crenata, C. mollissima. Literature: Kawamura, E. Bacterial blight of chestnut (Japanese with English resume). Ann. Phytopath. Soc. Jap.3:15-21. 1934. Needle Cast of Larch Mycosphaerella larici-leptolepis K. Ito & K. Sato. The earliest indi- cation of the disease usually occurs during the first week in July. Generally, scattered spots on the needle are first infected. They are at first minute, brown, and surrounded by a faint yellow halo. As the disease progresses, these spots increase in size and coalesce to attain a width of 1 mm. or more. Lesions are present 5 to 7, rarely 20 per needle. The discolored needles bear small black fruit spermogonia on the upper surface of the dead area. From a distance the infected trees a the appearance of having been scorched by fire or injured by late ost. 48 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Spermogonia, 83-165 < 74-143y, are formed on both green and fallen needles throughout autumn and winter. The mature spermogonia are filled with a great number of hyaline, rod-shaped spermatia, 3-5 X 0.5-1p in size. Perithecia are produced on the fallen needles in contact with the soil. Karly in March structures that are interpreted to be perithecial initials are observed. Perithecia develop either singly or in groups, at first embedded within the host tissue, but later becoming erumpent. Ascospores mature in May to July. Mature perithecia are amphige- nous, single or in groups, partially erumpent, globose, 88-157 X 84- 142u. Asciare clavate-cylindrical, 49-99 < 7-12, contain 8 ascospores. Paraphyses are absent. Ascospores are hyaline, unequally two-celled, constricted at septum, 11-18 X 3-5p. This is one of the most important diseases of larch forests. The characteristic symptom of this disease is a browning of the needles over all or part of the crown. This browning is most conspicuous in sum- mer and autumn and gives the impression that the tree is dying. Later the diseased needles drop off, leaving the trees with all or portions of their crowns thin and the remaining needles confined to tufts at the end of the branches. Repeated serious defoliations bring about a consid- erable decrease in growth increment. The source of infection is diseased needles, and intercontinental spread may be possible by seedlings and stocks bearing needles. Range: Northern and central parts of Japan. Hosts: Pinaceae (species listed in order of susceptibility )— Larix decidua (Planted in Japan) L. gmelini var. olgenis (Planted in Japan) L. gmelini var. japonica L. leptolepis (L. kaemphert) Literature: Ito, K.; Sato K.; and Ota, N. Studies on the needle cast of Japanese larch—I. Life history of the causal fungus, Mycos- phaerella laricileptolepis sp. nov. Bul. Govt. Forest Expt. Sta. 96 :69-88. 1957. Shoot Blight of Larch Physalospora laricina Sawada. Stems of seedlings and shoots of young trees are attacked. Lesions are more or less sunken and fre- quently exude resin. Diseased stems and twigs are girdled, killed, and then defoliated. Many dieback twigs are seen in the crowns of heavily diseased trees. Perithecia are produced under the epidermal tissues of killed twigs and stems. Perithecia are black, globose, erumpent, 3684 in diameter. Asci are clavate, rounded at apical portion, hyaline, 114-135 X 22-26un. Paraphyses are 3» in diameter, rarely branched. Ascospores are elliptic, smooth, 24-27 X 13u. Imperfect stage, A/acrophoma, is found on both twigs and leaves. This is currently the most serious disease of larch forests in Japan. Though trees of all ages are susceptible, young trees are very heavily attacked. Infected trees are malformed and growth is greatly reduced. International spread may be possible by infected trees or scions. Importation of living plant material other than pollen or seed should be forbidden except for experimental use following rigorous inspec- DANGEROUS INTERNATIONAL FOREST TREE DISEASES 49 tion and retention in quarantine until all latent infections have had time to appear. Range: In Japan it is common from Hokkaido south to the Tohoku District. Hosts: Pinaceae (species listed in order of susceptibility )— Lariz decidua (Planted in Japan) L. gmelini var. olgenis (Planted in Japan) L. gmelini var. japonica L. leptolepis Literature: Sawada, K. Fungi inhabiting conifers in the Tohoku District IT. Fungi on various conifers except “Sugi’”. (Japanese with Latin Diagnoses) Bul. Govt. Forest Expt. Sta. 46: 111-150. 1950. Uozumi, T. Shoot blight of larch in Hokkaido (Japanese). Forest Protect. News (Tokyo), 7: 156-158. 1958. Anthraenose of Acacia Glomerella acaciae (K. Ito & Shibukawa) K. Ito (syn. Physa- lospora acaciae K. Ito & Shibukawa). Symptoms of the disease first appear on the plant as punctate brown lesions, which later enlarge and attain 5-10 mm. in diameter and become dark brown in color. The disease attacks all of the above ground parts of Acacia seedlings including leaves, stems, petioles, and branchlets. During wet periods the lesions elongate, coalesce, and very frequently girdle entire stems and petioles, causing a rapid wilting, early defoliation, and subse- quent death of the shoot. The fungous invasion of the young suc- culent shoot is especially rapid and severe. A number of the affected seedlings have dead tops with a few basal living branchlets. Un- der moist conditions, conidial masses of salmon pink color are abun- dantly produced on the lesions. About the end of October small dark brown to black perithecia are irregularly scattered on the surface of the dead area. Acervuli erumpent, scattered or gregarious, 100-140, in diameter, conidiophores hyaline, cylindrical or fusoid, 6-15 X 2-3u, setae among conidiophores, 1- or 2-celled, few or numerous, dark brown tapering at the apex 24-72 X 3-6y, conidia hyaline, straight with round ends, 12-18 X 4-6y, 1-celled. Perithecia single or in groups, partially erum- pent, globose, slightly papillate, 54-141 x 60-114, asci ovate-oblong with a collar extending into the apical wall, 8-spored, 36-60 X 6-9n, paraphyses broad in width, acute in apical portion, 39-55 X 3-8u, ascospores hyaline, ovate or elliptical, arranged irregularly, 1-celled, 10-15 X 3-6. This is the most serious disease of Acacia seedlings (especially A. dealbata) in Japan. Losses are very heavy, more than 90 percent mor- tality in some nurseries. One of the most important features of this disease is the penetration of the pathogen into the seed, where it may pass the winter as a dor- mant mycelium. The fungus is usually detected in about 5 percent of the seeds collected in Kyushu. The infected seeds are thus the most important sources of the primary infections, which appear in the nurs- eries. It has been thought that the causal organism might be im- ported from abroad with seeds into Japan. In importation of Acacia 50 _ U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 seeds, seed treatment with disinfectants or hot water bath is necessary for anthracnose-free countries. Range: Central and southern districts of Japan. Hosts: Leguminosae— Acacia dealbata A. mollissema Literature: Ito, K., and Shibukawa, K. Studies on some anthrac- noses of woody plants—III. A new anthracnose of Acacia with special reference to the life history of the causal fungus. Bul. Govt. Forest Expt. Sta., 92 : 51-64. 1956. Leaf Blotch of Poplar Septotinia populiperda Waterman & Cash. Symptoms first appear in early spring as small brown spots on the young leaves, frequently at or near the margin, but also at any point on the leaf blade. The spots usually increase rapidly in size, soon become gray at the center, and have an irregular but sharply defined margin. On the most susceptible species and hybrids, large areas of the leaf blade become invaded by the fungus. On the lower surface, the leaf blade and particularly the veins in the affected area become dark brown with white sporodochia. On the upper surface, small white masses of conidia appear, usually de- veloping in concentric circles. Along the margin of the blotch, white mycelial fans are frequently formed just below the cuticle of the upper leaf surface. Two or more of the spots may coalesce, resulting in al- most complete invasion of the leaf tissue. Early defoliation usually follows, and the young shoots of the most susceptible poplars may thus be entirely defoliated by latesummer. On the fallen diseased leaves on the ground, thin, small, black sclerotia of the fungus are abundantly produced in late October. For morphological characteristics of the pathogen, see Waterman and Cash (1950). In 1956, the first collection of this disease in Japan was made in Tokyo. Since that time, further surveys showed a more extensive distribution of the disease. Now, the fungus is distributed widely throughout Japan almost everywhere poplars are cultivated. Leaf blotch is the most important disease of poplar leaves and causes severe damage. Japanese pathologists believe that the pathogen was prob- ably imported with cuttings from Europe or America to Japan after World War IT. International spread is chiefly by cuttings, and imported cuttings must be surface sterilized before planting. Distribution: Japan, North America, Europe. Host: Salicaceae. Susceptible: Populus simonii, P. koreana, P. davidiana X P. canes- cens, P. tremula X P. tremuloides, P. canadensis, P. serotina, P. regenerata, P. marilandica, “Rochester” poplar, P. euramericana, I-455, I-214, I-154, I-293, LK-79, LW—-42, “Wettstein” poplar, “Jacometii” poplar, P. japonogigas, P. eugenii, P. berolinensis. (All planted in Japan). Very susceptible: P. nigra Xmawximowiczti (Kamabuchi-1,2), P. charkowiensis Xtrichocarpa, P. robusta, P. gelrica, “Leipzig” poplar, P. nigra Xlaurifolia (All planted in Japan). DANGEROUS INTERNATIONAL FOREST TREE DISEASES 51 Literature: | Waterman, Alma M., and Cash, Edith K. Leaf blotch of poplar caused by a new species of Septotinia. Mycologia 42: 374-384. 1950. Ito, K. Parasitic diseases of poplars in Japan. Forestry Agency of Japan, 22 pp. 1959. Violet Root Rot Helicobasidium mompa Tanaka. Slender roots attacked by the fungus become yellowish-brown or blackish-brown in color. They are softened, rotted, and finally disappear. In the case of severe dam- age, the cambial portion of large roots is heavily destroyed, only the woody tissue and the bark with no trace of small roots remain. On heavily affected roots, a great number of sclerotia buried in the cork layer are seen very frequently. Purple rhizomorphs creep up the surface of the roots and the trunk, increasing in diameter towards the ends. When the roots are severely injured it is not rare for numerous small roots to develop. Diseased plants may thus escape death at least temporarily. Soon after the aggregation of rhizomorphs reach the basal portion of the host, they develop into a mycelial mat or a sporophore. The sporophore formed on the basal part of the tree spreads upwards as well as sidewards covering the surface of the trunk. During May to July, the formation of the hymenial layer causes the surface of the sporophore to become powdery white. Many of the diseased trees at first show no remarkable changes in appearance above the ground, but, by and by, some of them are noticeably weakened and finally killed. In heavily affected trees, the leaves become more or less smaller, yel- lowish, and fall earlier than in the healthy ones. In extreme cases the entire subterranean portion of the diseased plant is almost com- pletely destroyed by secondary invasion of wood-rotting fungi. Sporophores develop around the basal portion of the trunk up to a height of 10 cm. or more, sometimes leaving here and there narrow parts uncovered. They are sessile, resupinate, often irregularly lobed, velvety, and membranaceous. Surface of the fruit-body, which was deep purplish brown in early spring, becomes whitish or light pink in color during the later part of the same season. In spore-bearing sporophores, four or five layers are anatomically distinguished. Ba- sidia do not arise from preformed resting cells, probasidia. Young basidia are hyaline, smooth, erect, club-shaped; mature basidia are curved, generally 3-septate, 30-50 X 5-10y, the 4 sterigmata are elon- gated, narrowed towards end, 10-15y long, tetraspored. Basidio- spores are hyaline, ovoid, slightly curved, 12-25 X 5-9» in size. This is one of the most important soil-borne diseases in Japan. A\|- most all tree species are susceptible. Spread of this disease 1s mainly by translocation of infected seedlings or stocks. Many different con- trol practices have been tried and recommended at various times, but most of them have proved either ineffective or only partially success- ful. Distribution: Japan, Korea, and Formosa. Hosts: Over 100 species, both ligneous and herbaceous, belonging to various genera are known as the hosts of the fungus. Some woody hosts containing introduced species are listed as follows: ; ; ) 52 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Ginkgoaceae—Ginkgo biloba (very susceptible) Pinaceae— Picea excelsa (Planted in Japan) Larix leptolepis Pinus parviflora, P. densiflora (very susceptible) P. strobus (very susceptible) (Planted in Japan) P. taeda (very susceptible) (Planted in Japan) Taxodiaceae—Cryptomeria japonica Cupressaceae—7huja occidentalis, Chamaecyparis obtusa Salicaceae— Populus maximowiceu, P. nigra (Planted in Japan) P. nigra X P. maximowiczui (“Kamabuchi”-1) (very suscepti- ble), Salix bakko Juglandaceae— Juglans sieboldiana (very susceptible) Platycarya strobilacea Fagaceae— Castanea crenata (very susceptible) C. mollissima (very susceptible) (Planted in Japan) Quercus acutissima Ulmaceae— Ulmus pumila Celtis sinensis Moraceae— Broussonetia kazinoki (very susceptible) Ficus carica F. elastica Morus alba (very susceptible) Magnoliaceae—Liriodendron tulipifera (very susceptible) (Planted in Japan) Platanaceae—Platanus orientalis Rosaceae— Malus pumila (very susceptible) Prunus serrata (very susceptible) Leguminosae— : Cercis canadensis (Planted in Japan) Robinia pseudoacacia (very susceptible) (Planted in Japan) Anacardiaceae—Phus vernicifua (very susceptible) Aceraceae—A cer campestris (Planted in Japan) Literature: Ito, K. Studies on ‘“Murasaki-monpa” disease caused by Helico- basidium mompa Tanaka. Bul. Govt. Forest Expt. Sta. 48: 1-126. 1949. Suzuka, N., et al. Studies on the violet root rot of sweet potatoes. (Japanese with English resumé.) Bul. Natl. Inst. Agr. Sci. Sr. Cxsalalis 95 Needle Blight and Canker of Cryptomeria Cercospora cryptomeriae Shirai. First symptoms on seedlings are brownish discoloration in needles and stems. Infected needles and twigs become dark brown and die. Under favorable moisture con- ditions, needle and twig blight progresses rapidly and causes the death of seedlings. Young, vigorously growing shoots and stems become infected around the base of a diseased needle or small twig. ~ — eee - ee ee ee DANGEROUS INTERNATIONAL FOREST TREE DISEASES 53 The affected area becomes blackened and slightly depressed. As the tissue dries, it turns dark brown. Stems less than 10 mm. in diameter may be girdled by the fungus in one growing season. Dark greenish fruit-bodies of the causal fungus are produced abundantly on the diseased needles and cankers of seedlings. As cankers increase in size, the cambial tissue may be killed inward, producing a flat-faced canker, swollen at the sides, and distorting the stem. These cankers usually are perennial and increase longi- tudinally for many years. Frequently the rapid growth of the stem tissue prevents the girdling of the stem, and trees may live for many years with one or more disfiguring but non-girdling cankers. Stromata dark brown, semi-spherical, fascicles dense, conidiophores light yellowish-brown, rarely septate, non-branched, 4-6 x 40-80y, conidia pale yellowish-olivaceous, obclavate to obclavate-cylindric, straight or slightly curved, echinulate, 3 to 7 septate, 5-9 * 30-85p. This is the most important disease of conifers in Japan. Seedlings and young trees are very susceptible. Infected seedlings are killed by blighting and canker. Losses are very heavy, up to 90 percent mortality in many nurseries. Intercontinental spread is possible through shipment of infected trees or cuttings. The causal fungus is very similar to Cercospora sequoiae Ellis & Ev. described on Sequoia gigantea in the United States of America. Spraying with fungicides in the nursery is very effective for control of the disease. Distribution: Japan, Formosa. Hosts: Taxodiaceae— Cryptomeria japonica Sequoia gigantea (Planted in Japan) Literature: Ito, K. The cause of canker of Cryptomeria japonica (Japanese). Plant Protect. (Tokyo) 6: 176-179. 1953. , Shibukawa, K., and Kobayashi, T. Etiological and patho- logical studies on the needle blight of Cryptomeria japonica I. Morphology and pathogenicity of the fungi inhabiting the blight- ed needles. (Japanese with English resume.) Bul. Govt. Forest Expt. Sta. 52: 79-152. 1952. , Shibukawa, K., and Kobayashi, T. Blight of Sequoia gi- gantea seedlings caused by Cercospora cryptomeriae Shirai (Japanese). Jour. Jap. Forest Soc. 40: 407-410. 1958. Needle Blight of Pine Cercospora pini-densiflorae Hori & Nambu. Yellowish-brown to gray lesions appear mostly on the upper half of the needle as the disease progresses, especially on 1- to 3-year-old trees. The needles die to such an extent that it is known as “leaf-blight.” _ Dark brown stromata fill the stomatal openings or as large as 60x in diameter, fascicles dense to very dense; conidiophores dark brown, rarely septate, not branched, sparingly geniculate, 2.5-5 xX 1045p; conidia pale yellowish olivaceous, obclavate to obclavate-cylindric, straight to curved, 3-7 septate, rounded to obconically truncate base, obtuse tip, 3-6 X 20-60p. This is the most serious disease of pine seedlings. Heavily infected seedlings die. Losses are heavy, up to 80 percent mortality in some nurseries. 54 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 International spread is possible only through shipment of infected seedlings. Controls by spraying with Bordeaux mixture or other fungicides are successful. Distribution: Japan: Kyushu, Shikoku. Formosa: Shizuoka. Hosts: Pinaceae. Susceptible: Pinus densiflora, P. thunbergti, P. massoniana (Planted in Japan), P. luchuensis. Very susceptible: P. radiata, P. strobus, P. pinaster, P. canariensis (All planted in Japan). Literature: Chupp, C. A monograph of the fungus genus Cercospora, Ithaca, New York. 440 pp. 1953. Nukumizu, T. Needle blight of pine (Japanese). Forest Protect. News (Tokyo) 5: 264. 1956. Ito, K. Diseases of Pinus strobus in Japan. (Japanese). Jb2d., 10: 43-46. 1961. The following five diseases are listed but not described. Detailed information on them will be supplied upon request to the authors. Virus Disease of Chestnut Virus (No specific name) Distribution: Japan (Ibaragi and Yamagata Prefectures). Hosts: Castanea crenata, C. mollissima. Gall Rust of Pine Cronartium quercuum Miyabe Distribution: Japan, Formosa, Korea. Hosts: Pinus densiflora, P. thunbergii, P. sylvestris (Planted in Japan). Alternate hosts: Quercus, Castanea, Cyclobalanopsis, Shiia. Needle Rust of 5-Needle Pine Coleosporium paederiae Diet. Distribution: Japan, Formosa. Hosts: Pinus strobus (Planted in Japan). Alternate host: Paederia chinensis. Brown Spot of Tung Cercospora aleuritidis Miyake syn. Mycosphaerella aleuritidis (Mi- yake) Ou. Distribution: Japan, China, etc. Host: Aleurites fordii. Needle Blight of Redwood Cercospora exosporioides Bubak. Distribution: Japan (Kyushu and Tokyo), ete. Hosts: Sequoia sempervirens (Planted in Japan). Larix leptolepis. DANGEROUS FOREST DISEASES IN INDIA B. K. Baxksut Head, Division of Forest Protection, Forest Research Institute, New Forest (Dehra Dun), India Spike Disease of Sandal Virus (No specific name). A serious virus disease of sandal (Santalum album 1.) in south India. The symptoms first appear in one or more branches, in which new leaves become progressively re- duced in size, pale and stand stiff and crowded on shortened internodes, giving a spikelike appearance. Spike eventually spreads over the entire tree which exhibits continuous growth. In advanced stages of disease, flowers and fruits do not develop. If a branch is spiked after inflorescence is formed, fruits become reduced in size, or flowers exhibit phyllody. Haustoria and fine root ends die. In spiked branches and leaves, starch is significantly more, while nitrogen and ash less than in normal leaves. The spiked tree never recovers and dies in a few years. Disease is transmitted by grafting and not communicable by sap transmission. Intracellular cell inclusions are demonstrated. The claim that /assus indicus is a vector for the disease is not confirmed and any other insect is yet unknown. Several plants show symptoms of spike and some of them serve as hosts for sandal. Eradication of diseased trees or lopping spiked branches does not reduce incidence of disease. Marking out susceptible and resistant hosts, and propagating sandal on the latter is suggested. However, some principal susceptible hosts like Lantana camara, are excellent nurse crops for sandal and their eradication is practicable. Natural selection of resistaz.t trees and propagating them through seeds has not controlled the disease. In nature, sandal grows healthy, free from spike under shade. Control of spike may be attempted by raising sandal under a light canopy of trees to serve as good sandal hosts and at the same time afford some degree of resistance to spike. The disease has killed sandal in large tracts in south India. It spreads in the direction of wind. Although sandal is now naturalized in India, it is suggested that it was introduced from Java in the remote past. The disease may have occurred naturally on some native plants, where it is harmless, and from which it transferred to sandal, finding _the exotic highly susceptible. The disease is known only in India. Not reported from Malaysian islands and Australia where sandal occurs naturally. Export of living sandal from India except seeds for experiment should be forbidden. Hosts: Santalaceae—Santalum album L. Literature: Coleman, L. C. Spike disease of sandal. Mycol. Ser., Bul. 3, Dept. Agr., Mysore State. 1917. Deodar Witches’-Broom Peridermium cedri (Barclay) Sacc. A needle rust of deodar (Cedrus deodara Loudon). Attacks young needles of the current 55 56 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 year’s shoots. Needles become short and curved and shed earlier than normal, so that foliage is thin. Affected branches and, rarely, the en- tire tree is transformed into witches’-brooms. Causes large-scale mor- tality, particularly in young trees, or death of affected branches in large trees. The rust is known only as pyenia and aecia on deodar. Pyenia abundant, superficial, 0.08 mm. broad, 0.04 mm. deep. Aecia 10 to 127 on each needle on upper surface, in one row on one or the other side of the middle line, but at distal end in two rows. Aecia are superficial, up to 0.5 mm. broad and 0.16 mm. deep. Aeciospores in chains, yellow with orange-yellow granular contents, round or oval, 15-21 X 1417p. The epispore is thick and striated. The aeciospores ripen in May-— June. Pseudoperidium is delicate, 1-cell thick, and falls apart soon. This is a serious disease of deodar in the western Himalayas in India, particularly under wet conditions. Overwintering of aecio- spores does not occur. The fungus overwinters as mycelium in the needles and in the shoots containing them, to infect new needles in the next season. Systematic removal of diseased plants or affected branches has been found to bring the disease under control. Deodar is grown as an exotic in America and elsewhere. Importa- tion of living plant material other than seed should be forbidden in foreign lands. Hosts: Pinaceae—Cedrus deodara Loud. Literature: Troup, R.S. Peridermium cedri as a destructive fungus. Indian Forester 38: 222-993. 1912. Jbid., 40:469-472. 1914. Chir Pine Blister Rust Cronartium himalayense Bagchee. a eS) F. pennsylvanica Marsh_-___-_-~__-|-__-=------- Moderate Intermediate Catalpa speciosa Warder________- Moderate__- Yigts: owe FF _ Do. Juniperus virginiana L_________- i (a ie on Resistant Gymnocladus dioicus (L.) K. |------------ Resistant___--| Susceptible Koch. Populus deltoides Bartr____----~-- Vary_2 <1) Eixteeniets 9.0 Do. Ulmus americana L____-_---_- Baek of week [it's | eee oO. ST TVS Ss arse Resistant_-_ _- Intermediate Lo Tia pel inl gl cg Very___- Extreme___-__- Susceptible emmecementaies Be OL OP ee Resistant____- Resistant meneperus faccida Schiecht__-.___|___+___+____}__-- da Sees ai ig,. 52ehs o OE ES Se a a ee ae Sit oe Resistant Robinia pseudoacacia L_________ 7 sas ee Sues es Susceptible Gleditsia triacanthos L___________|--- SO Led aed i | fot Do. Morus alba var. tatarica_________ Moderate___ Hick ae G3 8. Intermediate Eleagnus angustifolia L_________- Slight__ _._- Hessel + __| Susceptible Maclura pomifera (Raf.) Scheid__|___ | ee LAA | ae Do. enree War ayinesaee Oy Moderate So thy inte fy 0 TE a es ee eee | oe ee || ee | Intermediate SE Ts a eee ae. eee Sascepibie. _.| Susceptible Eeeponderosa Laws______ _______- ee See eee | |) eee ee Do. Caragana arborescens___________- ito} aie Signe’ Se ae Slight a drummondit Hook. & |____________ Extreme_____- Resistant n. | | a | erent oe ot le See eee ee Platanus occidentalis L_________-_ S17G TT NS | I, ae el ee a RE ei ee) as ee eeaske 2 Intermediate INT a Se |e gia d Bs (ESE; |) ee Fe ee ee se Op ES a Moderate___| High______-__-_ Intermediate Chilopsis linearis (Cav.) Sweet__| Resistant___|______________ Resistant Control.—Losses from root rot in agricultural crops can be lessened to some extent by soil acidification, deep cultivation, crop rotations with monocots such as wheat, and addition of organic matter. For trees and shrubs in shelterbelts, no definite reduction is possible ex- cept perhaps by alternate planting of resistant with less resistant trees in a checkerboard pattern. Plants grown in root-rot areas should not be shipped elsewhere to similar climatic zones. Literature: Shear,C.L. The life history of the Texas root rot fungus, Ozoniwm omnivorum Shear. Jour. Agr. Res. 30: 475-477. 1925. Streets, R. B. Phymatotrichum (Cotton or Texas) root rot in Arizona. Univ. Ariz. Tech. Bul. 71: 299-410. 1937. Taubenhaus, J. J., and Ezekiel, W. N. A rating of plants with ref- erence to their relative resistance or susceptibility to Phymato- trichum root rot. Tex. Agr. Expt. Sta. Bul. 527,50 pp. 1936. 687-137 O—63—__8 108 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Wright, E., and Wells, H. R. Tests on the adaptability of trees and shrubs to shelterbelt planting on certain Phymatotrichum | root rot infested soils of Oklahoma and Texas. Jour. Forestry 46: 256-262. 1948. Poria Root Rot of Douglas-Fir G. W. WALLIs Forest Entomology and Pathology Branch, Canada Department of Forestry, Victoria, British Columbia Poria weirii Murr. is a root rot of coniferous species common in Northwestern United States and southern British Columbia, Canada. The disease occurs in patches or centers of infection. Aboveground symptoms become apparent only after the disease has reached an ad- vanced state. Shortening of the leader growth, sometimes accom- panied by a distress crop of small cones on Douglas-fir, is followed by a thinning and yellowing or reddening of the foliage, and finally by death of the tree. Windthrow of living trees is common, the major decayed roots breaking close to the root collar. Sporophores, forming on the underside of decayed logs and up- rooted stumps, are found only periodically during the summer and early autumn. The resupinate fruit bodies are cinnamon buff to brown, usually with a broad to narrow white to cream sterile margin. On species other than western red cedar the sporophores usually form only a single tube layer; on cedar a perennial fruit body is formed. Setal hyphae and setae are abundant. Basidiospores are globose to subglobose becoming oblong-ellipsoid with a small apiculus, 44.9 X 2.8-3.2u. No conidiospores are formed either in nature or in culture. Hyphae have simple septa, branching frequently immedi- ately below the septum, but with no clamp connections. The incipient stage of the decay is usually characterized by a cres- cent-shaped to spherical pattern of reddish-brown stain in the cross section of the stump. In the advanced state of decay, the wood breaks down to a yellow, laminated, pitted rot. Setae and setal hyphae are abundant in the laminated wood and a brown crustlike sheet often forms over mycelial masses on exposed wood surfaces. This fungus, although capable of causing death to the majority of coniferous species in the Douglas-fir region, is most important as a root rot causing extensive losses in 25- to 125-year-old Douglas-fir and as a butt rot of cedar. The infection arises when roots contact the fungus present in roots and stumps of the previous crop. Spread to adjacent trees occurs when a healthy and diseased root are in contact. The role of basidiospores in the spread of infection is as yet unkown. It has been estimated that the productivity of second-growth Douglas-fir stands in western Washington and Oregon is, on the average, reduced by about 5 percent as a result of the activity of this fungus. A method for the economic control of Poria root rot is, as yet, unknown. Intercontinental spread is possible through shipment of infected logs. Infection of seedlings below 6 years of age is not known. DANGEROUS INTERNATIONAL FOREST TREE DISEASES 109 Range: In North America it is common throughout the range of Douglas-fir in southern British Columbia, Canada, and north- western United States. In Japan it is found in the subalpine forests of Honshu and the primeval forests of Middle Hokkaido. Hosts: Pinaceae— | ; North America: Pseudotsuga menziesii (Mirb.) Franco Abies grandis Lindl. Tsuga heterophylla (Rafn.) Sarg. Pinus monticola Dougl. Abies amabilis (Dougl.) Forbes Abies lasiocarpa (Hook.) Nutt. Pinus ponderosa Laws. Picea sitchensis (Bong.) Carr. Larix occidentalis Nutt. Japan: Tsuga diversifolia (Maxim.) Mast. Abies mariesti Mast. Abies sachalinensis Mast. Picea jezoensis (Sieb. & Zucc.) Carr. Cupressaceae— Thuja plicata D. Don Chamaecy paris sp. _ Literature: Aoshima, Kiyowo. Wood-rotting Poria from Japan II. Govt. Forest Expt. Sta. Bul. 59, Tokyo, Japan. 1953. Buckland, D. C., Molnar, A. C., and Wallis, G. W. Yellow lam- inated root rot of Douglas-fir. Canad. Jour. Bot. 32: 69-81. 1954. Childs, T. W. laminated root rot of Douglas-fir. U.S.D.A., Forest Service, Forest Pest Leaflet 48. 1960. Mounce, Irene, Bier, J. E., and Nobles, Mildred K. A root-rot of Douglas-fir caused by Poria weirii. Canad. Jour. Res. C, 18: 522-533. 1940. Fir Tip Blight M. E. Fow er Forest Service, U.S. Department of Agriculture, Upper Darby, Pennsylvania Rehmiellopsis balsameae Waterman is a blight of the current sea- son’s needles of several species of fir in Northeastern United States. The disease, which affects all sizes and ages of fir trees, appears first on the lower branches; usually the lateral twigs of these branches are more severely affected than the terminal twigs. Severe infection re- peated for several years may result in the death of small trees; large trees are rarely killed. The disease causes relatively little damage to trees but may be very disfiguring and damaging to ornamen- als. _ Weather conditions exert an important influence on disease sever- ity. A late, moist growing season leads to rapid development. of young succulent tissue that is particularly susceptible to infection and 110 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 damage. An early growing season or one with limited rainfall re- | sults in less disease buildup. The earliest symptoms appear on needles of the current season’s | growth when the bud scales begin to slough off. Yellowish-pink spots show on the needle tissue uncovered by the loosening bud scales. The young, developing twig, bearing these needles, usually continues to grow for a time, but before reaching maturity may turn dark brown or black and become shriveled, slightly curved, and brittle. Needles. on such twigs change in color from light green to yellowish pink, then to dark reddish brown, and finally to gray. As these color changes ») occur, the needles dry out and their margins roll backward toward | the lower surface, thus appearing narrower than healthy needles. They also frequently curve or bend. Adventitious buds may develop | below the dead tips and produce weak, stunted needles late in the sea- son. Infected needles are very brittle, but most of them overwinter » on the twigs for one season and sometimes two. The fungus may enter the twig tissue from an infected needle on | Abies concolor, producing small cankers around leaf scars. Such cankers have not been observed on other species of fir. | About a month or 6 weeks after the first evidence of the disease, | small, black fruiting bodies of the fungus appear in the tissue of the upper leaf surface. These develop slowly during the summer and reach maturity the following spring. The fruiting bodies also de- velop on shriveled twigs and on the small cankers at the base of in- | fected needles. Ascospores are dispersed at the time new needles are being produced. The fir tip blight in North America is very similar to the blight previously known in Europe. The causal organism is a distinct species from the European Rehmiellopsis abietis (E. Rostr.) O. Rostr. (Syn: R. bohemica Bub. & Kab.) with which it was once confused. The ascomata, asci, and ascospores of the American species are larger than the European. The ascomata of 7. balsameae are 200-250,» in diam- eter. The asci are conspicuously thickened at the apex, being 5 to 8u at the thickest point. The 16-spored asci are 81-141 X 33-41p. The fusiform-elliptic ascospores are hyaline, 1-septate, cells unequal, some- times slightly constricted at the septum, densely granular, straight or Sunuee and 31.5-49.9 X 6.3-12.6u. A conidial stage has not been observed. Hosts and Range: Pinaceae— Abies concolor (Gord. & Glend.) Lindl. in Maine, New Hamp- shire, Massachusetts, Rhode Island, and New York. A. balsamea (L.) Mill. New England States and New York. A. cephalonica Loud. Rhode Island. A. procera Rehd. Massachusetts. A. fraseri (Pursh.) Poir. Massachusetts. Literature: Waterman, Alma M. New hosts and distribution of Rehmiellopsis bohemica. Phytopath. 27 : 734-736. 1937. Tip blight of species of Abies caused by a new species of Rehmiellopsis. Jour. Agr. Res. 70 (10) : 315-3837. 1945. , and Aldrich, Kenneth F. Rehmiellopsis needle blight of balsam fir in Maine. Plant Dis. Rptr. 24: 201-205. 1940. , and McKenzie, M. A. A disease of Colorado fir. Phyto- pathology 23: 108-109. 1933. Si — SR =~ DANGEROUS INTERNATIONAL FOREST TREE DISEASES Pht Brown-Spot Needle Blight A. F. VERRALL Forest Service, US. Department of Agriculture, New Orleans, Louistana Scirrhia acicola (Dearn.) Siggers is a needle spot and dieback mainly of Pinus palustris before height growth starts. The common spot is straw yellow at first, often with chestnut-brown borders which may become dark purplish in autumn; individual spots are about 3 mm. across but several often coalesce, and as the needles die from the tips, the green tissue between spots shrinks more, resulting in an embossed appearance. Some spots consist of an amber-yellow band with a small brown center. Conidial stage is Lecanosticta acicola (Thum.) Syd. Acervuli in- nate-erumpent, at first globose, 50-100u across, becoming elongate up to 1.5mm. Conidia mostly 1-3 septate, sickle-shaped, 0.5-4 * 27-32n, pale brown, discharged through clefts in epidermis in sticky matrix, disseminated mostly by rain splash. Ascigerous stage: stromata compact, linear, non-clypeate, innate- erumpent, 1-18 locules mostly in single row, 40-80» diameter, not dis- tinctly ostiolate; asci aparaphysate, 6-9 X 30-35y, 8-spored; spores hyaline, 1-septate, oblong-cuneate, 3-4 X 9-16y. Ascigerous locules often develop marginally to acervuli. Conidia produced all year; ascospores mostly in winter and spring. Brown spot is one of the major obstacles to the successful regenera- tion of Pinus palustris over wide areas in SE. United States. The disease causes chronic defoliation which either kills seedlings or delays initiation of height growth for many years. This pine is typically very resistant after reaching a height of 75 cm. P. taeda may be heavily attacked at all ages but most dieback occurs in the lower crown late in the growing season and, therefore, is less deleterious. Occasionally the fungus causes serious needle dying on other pines, including P. strobus. Intercontinental spread through shipment of seedlings is highly probable, for even with rigid fungicidal spraying some infection occurs _ I most pine nurseries. Pollen and seed shipments appear safe. Range: Common in the coastal States from North Carolina to Texas, Also reported inland as far as Missouri and Ohio. Occasionally in SW. and NW. United States. Hosts: Pinaceae— Pinus palustris Mill. P. taeda L. P. elliottii var. elliottii Little & Dorman P. strobus L. P. echinata Mull. P. glabra Walt. P. rigida Mill. P. serotina Michx. P. virginiana Mill. Also occurs on following introductions to eastern United States: P. attenuata Lemm. P. contorta Doug]. 112 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 P. coultert Don P. halepensis Mill. P. jeffreyi Grev. & Balf. P. latifolia Sarg. P. nigra poiretiana (Ant.) Aschers. & Graebn. P. muricata Don - P. pinaster Ait. P. pinea L. P. ponderosa var. scopulorum Engelm. P. radiata Don P. sabiniana Dougl. P. sylvestris L. P. thunbergii Parl. Literature: Siggers, P. V. The brown spot needle blight of pine seedlings. | U.S. Dept. Agr. Tech. Bul. 870: 1-36. 1944. Wolf, F. A., and Barbour, W. J. Brown-spot needle disease of | pine. Phytopathology 31: 61-74. 1941. Septoria Canker of Poplars J. EK. Brer Department of Biology and Botany, University of British Columbia, | Vancower, British Columbia Septoria musiva Pk. (Perfect Stage—Mycosphaerella populorum G. E. Thompson) is a leaf disease and perennial stem canker of exotic and hybrid poplars in North and South America. The first leaf lesions appear from 3 to 4 -weeks after the opening of the buds, mostly confined to leaves on the lower branches. Later the infection | becomes general throughout the trees. The fungus produces necrotic — spots of various shapes and sizes which often coalesce to involve large | areas of the leaf. The individual lesions are brown with yellowish | to white centers, and small black pycnidia develop throughout the | lesions on both leaf surfaces. Under moist conditions the conidia are | discharged from the pycnidia as curled, pinkish cirri. The conidia are hyaline, continuous to four (mostly two) septate, measuring from 17 to 57 long. ) The canker stage originates in the bark of twigs of the current year, entering the host through mechanical wounds, lenticels, stipules, or leaf petioles. By early summer a very conspicuous symptom is the presence of one or more dead leaves on the leaders, at the ring scars, or on the axillary branches produced on 2-year-old stems. At the bases of the dead leaves cankered bark is evident, which is usually black, frequently enclosing yellowish to white areas in which the pycnidia may be found. The cankers may girdle and kill the leader and axillary branches during the first year and later spread from the axillary branches into the main stems. On entering the main stem the pathogen may produce a perennial canker resulting in considerable malformation of the main stem. Isolations from the diseased bark at the margin of older cankers frequently produce cultures of Cytospora chrysosperma (Pers.) Fr.. and it is possible that advanced cankers may result from a combined attack of Septoria and other fungi such as Cytospora. DANGEROUS INTERNATIONAL FOREST TREE DISEASES 113 Perithecia of the Mycosphaerella stage occur on overwintered leaves and on the cankered bark of 1-year-old stems. The asci, which contain 8 spores, are cylindrical, short stipitate, from 51-73y * 12-17p. The ascospores are hyaline, one-septate, measuring from 17-24, * 4-6z. This disease has caused serious losses on exotic and hybrid poplars in eastern and central North America. Although trees of all ages are susceptible, the canker stage is restricted to the bark on younger stems and branches. Intercontinental spread is possible through shipment of infected trees or cuttings or of infected bark on logs or lumber. Importation of living plant material other than pollen or seed should be forbidden except for experimental use following rigorous inspection and reten- tion in quarantine until all latent infections have had time to appear. Export logs and lumber should be debarked. Range: In North America it is common in eastern and central Canada and the United States. In South America it occurs in Argentina. Hosts: Salicaceae. Numerous exotic and hybrid poplars have been found to be susceptible particularly those with black, balsam, and cottonwood parentage. Literature: Bier, J. E. Septoria canker of introduced and native hybrid pop- lars. Canad. Jour. Res, C. 17: 195-204. 1939. Sarasola, A. A. Dos Septoriosis de las alamedas Argentinas. Rey. Argentina de Agron. 11: 20-43. 1944. Thompson, G. E. Leaf spot diseases of poplars caused by Septoria musiva and S. populicola. Phytopathology 31: 241-254. 1941. Waterman, Alma M. Septoria canker of poplars in the United States. U.S.D.A. Cir. 947. 1954. Strumella Canker of Oaks J. R. HansproucH Forest Service, U.S. Department of Agriculture, Washington, D.C. Strumella coryneoidea Sacc. & Wint. (Imperfect stage). Urnula cratertum (Schw.) Fries (Perfect stage). A perennial, usually non- girdling stem canker of Quercus in eastern North America. The first symptom is a yellowish bark discoloration centered around a dead branch or stub, usually with a raised margin and a depressed inner zone. On the tightly adhering bark near the center of the canker, small black nodules composed of interwoven hyphae are formed. They produce no spores. As the infected area enlarges, two types of lesions can result, target or diffuse, with frequent intergradations. Target-type cankers are most common and result from the forma- tion of successive ridges of callus in opposition to the slow growth of the fungus. These ridges form concentric circles around the base of the dead branch at the canker center. Usually there is a pronounced distortion or flattening of the cankered stem. The wood under the canker face slowly decays and eventually the bark sloughs off. Dif- fuse-type cankers occur when the fungus grows rapidly enough to girdle the stem before callus formation takes place, usually on stems that are under 4 inches in diameter. Water sprouts often appear be- 114 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 low the cankers. Small trees are killed but larger trees may remain alive for several decades or until the tree breaks at the canker. | The fungus rarely sporulates on living trees; however, if the tree _ dies, and while it is still standing, sporodochia are produced abundant- ly, both on the cankered area and beyond. They are dark brown, rounded, powdery pustules, 1-8 mm. in diameter, bearing stout branched conidiophores from the tips and sides of which are produced irregularly globose to pyriform, brown, spiny conidia, 6.7-8.1 X 4.7- 5.8u. These conidia do not germinate. They are windborne but their role in causing new infections is unknown. After infected trees fall, the Urnula stage is produced. The apothecia, always attached to decaying wood, are common and con- spicuous in early spring. They are up to 3 cm. in diameter and 4-6 cm. deep, black, leathery, rupturing irregularly. The asci are cylin- drical, with 8 one-celled, smooth, hyaline ascospores, 12-14 X 25-35y. Ascospores are windborne and germinate readily within a few hours after release from apothecia. Strumella canker is common but losses are not catastrophic. The fungus spreads slowly, seldom infecting more than 2 or 3 percent of the trees in an oak stand. Most cankers, however, occur on the first 12 feet of the trunk, seriously reducing or destroying the value of the butt log. Wind breakage of cankered trees occurs frequently. Con- — trol is through sanitation—removing infected trees in weeding, thin- nings, and harvest cuts. | Prevention of intercontinental spread of Strumella canker should not be difficult. Infected trees are distorted and the infected portion is seldom, if ever, harvested and utilized for anything other than fuel. Range: : In North America it is common in eastern United States. The fungus is reported as a saprophyte in eastern Canada, western United States, and one collection from Europe (Germany). Im- portant only on oaks. Hosts: Fagaceae— Quercus velutina Lam. QY. rubra L. . coccinea Muenchh. . dictfolia Wangenh. . macrocarpa Michx. marylandica Muenchh. prinus L. . prinoides Willd. . palustris Muenchh. . bicolor Willd. . alba L. Fagus grandifolia Ehrh. Castanea dentata (Marsh.) Borkh. Betulaceae—Ostrya virginiana (Mill.) K. Koch Tiliaceae—T2lia americana L. Cornaceae—Vyssa sylvatica Marsh. Aceraceae—Acer rubrum L. Juglandaceae— Carya glabra (Mill.) Sweet C. ovata (Mill.) K. Koch DDHHOOH9H9d9 DANGEROUS INTERNATIONAL FOREST TREE DISEASES 115 Literature: | Davidson, R. W. Urnula craterium is possibly the perfect stage of Strumella coryneoidea. Mycologia 42: 735-742. 1950. | Heald, F. D., and Studhalter, R. A. The Strumella disease of oak | and chestnut trees. Pa. Dept. Forestry Bul. 10,15 pp. 1914. | Hughes, S. J. Microfungi V. Conoplea Pers. and Exosporium Link. Canad. Jour. Bot. 38: 659-696. 1960. Dwarfmistletoes of Conifers | Jos Kutt Department of Biology and Botany, University of British Colum- bia, Vancouver, British Columbia Arceuthobium spp. are conifer-inhabiting flowering plants of the mistletoe family (Loranthaceae). Leaves are reduced to scales, op- posite, decussate, inconspicuous, same olive-green color as the stem. The internodes are round or rectangular in cross section, depending on species and age. The larger species (A. campylopodum and A. vaginatum) are com- monly up to 10 cm. long, while the smaller ones (A. douglasst and A. pusillum) ‘are usually no more than 1.5 cm. The plants are unisexual. Staminate flowers are about 24 mm. in size, 3- or 4-partite, deciduous, anthers sessile with ringlike archesporium around a central columella, pollen tricolpate, spinulose. Pistillate flowers are about 1 mm. in size, little differentiated, with two perianth segments greatly reduced, lip- | hike around the short and blunt stigma. Fruit at maturity is a re- | curved, turgid berry, ovate to elliptical in shape, with a conspicuous transverse color demarcation. The fruit is explosive, releasing the single seed upwards or obliquely away for many feet. The seed, which consists of a single cylindrical and largely undifferentiated embryo surrounded by a large amount of chlorophyllaceous endosperm, germinates on the surface to which it has become attached. If this surface is a young branch of a suitable host, the radicle penetrates into living tissue and a new individual develops. Since the remainder of the seed dies or falls away, dwarf- mistletoes have a completely internal stage which may last for more than a year. Flowering time varies for the different species, but ex- pulsion of the seed always takes place in the fall. The haustorial or endophytic system is a complex, ramifying system divisible into a longitudinal system of strands, external to and more or less parallel to the host cambium, and a radial system consisting of sinkers radially oriented in phloem and xylem, such sinkers taking their departure from cortical strands. Direct xylem-to-xylem connec- tions are common between the largely vascular older sinkers and the host tracheids. Cortical strands and perhaps all sinkers originate as uniseriate filaments of cells each with a single apical cell, but divisions in the more distal cells turn the strands into vasculated structures much like normal roots. Symptoms of the disease vary not only between species of dwarf- mistletoe, but also within one species when several host species are involved. The simplest response of the host is a localized, somewhat fusiform swelling. In this case the endophytic system is confined to 116 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 the swelling, the youngest tips growing outward near the poles of the spindle. Flowering shoots first appear near the original court of en- trance, but succeeding ones emerge in concentric zones of increasing diameter. The center of such an infection usually deteriorates and forms a court of entrance for various decay-producing fungi and bark beetles. Some dwarfmistletoes, but only on certain host species, call forth the production of a witches’-broom in which suppression of lateral branches is largely released, resulting in a dense growth of abnormal appearance. In many of such brooms the endophytic system of the dwarfmistletoe pervades all branches, even to penetration of the apical meristems of the host, and these mistletoe shoots are present in pre- dictable patterns along these host branches. In most instances the un- infected part of the tree deteriorates badly, leaving only the broomed portion alive. Since the susceptibility of many exotic conifers has been demon- strated and some native hosts are planted extensively abroad, the North American species of Arceuthobium pose a considerable threat. Fortunately. the seeds are not long-lived and lose their ability to adhere to new objects after some time, therefore the chance of estab- lishment on other continents by means of seed is small. A greater danger, perhaps, lies in the export of trees of nursery size, since these may bear invisible infections. Experience in North America has shown complete elimination of an infected stand to be the only possi- bility of eradication. Dwarfmistletoes are difficult to evaluate as to their economic im- portance. There is general agreement, however, on the severity of losses in certain areas, Field observations point to significant losses in the following instances: Hosts: Pinaceae Dwarfmistletoes Area Abrestsppvs= 25222 2% Arceuthobium campy- Sierra Nevada, California. lopodum. Picea: spp 2-2-2 25 Arconistllume ee eee s es Northeastern United States and across Canada to Manitoba. Pinussppeoe 2s A. campylopodum__._---- Eastern Oregon south through most Pacific and Southwestern States. P. banksiana, P. con- A americanwin. 5. Northern Alberta to Colo- torta. rado. Pseudotsuga menziesii. A. douglasti________---- Interior southern British Co- lumbia to northern Cali- fornia and the South- western States. Tsuga heterophylla___._ A. campylopodum-__-_---- Pacific Coast, Alaska to Oregon. A more complete listing of hosts is provided in Kuijt (1955). Literature: Gill, L.S. Arceuthobium in the United States. Trans. Conn. Acad. Arts & Sci. 32: 111-245. 1935. Kuijt, Job. Dwarfmistletoes. Bot. Rev. 21: 569-628. 1955. . Morphological aspects of parasitism in the dwarfmistle- toes (Arceuthobium). Univ. Calif. Pub. Bot. 30: 337-436. 1960. DANGEROUS INTERNATIONAL FOREST TREE DISEASES 117 Principles of Forest Disease Control | | J. S. Boyce Professor Emeritus of Forest Pathology, Yale University, New Haven, Connecticut, U.S.A. I feel presumptuous in discussing the principles of forest disease ntrol before this group since most of you are specialists in the field, nd therefore anything I can say will sound trite. However, there ill probably be some disagreement with my ideas, and reasoned disagreement is invaluable for the complete exploration of any topic. There is often such a difference in the effect of diseases caused by native pathogens on forests that control measures differ widely. For native diseases these measures are largely indirect—that is, applied as a part of routine silvicultural practice; whereas, for introduced diseases, direct measures must often be used—that is, special opera- tions solely against the disease. Whenever possible, indirect meas- ures should be employed. Diseases caused by native pathogens do not threaten the commercial extinction of a native tree species, but diseases caused by introduced fungi may eliminate, and in certain cases have eliminated, important timber species. Consequently, there is usually far greater urgency to control diseases caused by introduced pathogens than to check those caused by native pathogens. _ Control measures are limited since forest stands in general have a relatively low value considering the years required to produce them, therefore expenditures for disease control] must be modest. Thus, the intensive methods of disease control that are routine in agri- culture and horticulture are possible only occasionally in forestry— the exception being nurseries where intensive contro] measures are standard practice. Insofar as possible, control should be part of regu- lar silvicultural practice. __ Certain precepts should be pursued in order to minimize disease. _Each of us can cite exceptions to these precepts and, because of con- ditions in some forest regions, it may seem necessary to disregard | them. When this is done, it should be with realization of increased expenditures that may have to be made for disease control. Some of these precepts follow: } _ Seedling stands are better than sprout stands. Natural regenera- tion is better than artificial, particularly planting. Uneven-aged stands are better than even-aged. The selection system is better than clear cutting. Mixed stands are preferable to pure stands, and mix- tures of conifers and hardwoods are especially desirable. Natural stand composition should be followed as far as possible. Of course in certain forests nature’s method is pure stands which should be ac- cepted. Good sites are essential—no amount of care can produce a satisfactory stand on an unsatisfactory site. Native species are safer than exotics, because exotics are more liable to injury when conditions become critical. Because of the high risk of bringing in new patho- gens, exotics should be introduced as seed only. The seed must be of proper origin both as to location and character of the mother trees. Our safeguard against introduced pathogens is quarantines which admittedly are measures of delay and not measures of exclusion. 118 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 Nevertheless, delay is more important in forestry than in agriculture | because of the long time necessary to produce a crop of trees and to. work out control methods when disease does appear. The control or extermination of a pathogen by another pathogen— | that is, biological control—theoretically should be the cheapest and | most effective method of dealing with pathogenic diseases. Yet so far | there has been no instance of any worthwhile success in this field’ against fungi and related organisms, and nothing now appears promis- ing for the future. The development of resistant trees by selection or hybridization, | | when this can be accomplished, is probably the best method for con- | trolling disease. The limitations of the method are the necessity for || developing several resistant hybrids or selections and the long time this | requires. This means that in dealing with a disease caused by a |) virulent pathogen a successful method of control must be developed } quickly so the affected tree can be perpetuated until such time as suffi- cient resistant individuals can be obtained. | Finally a new and promising method of control is being developed; |) namely, the use of systemic fungicides. Lesions of white pine blister | rust on western white pine trees have been reported to be inactivated within 18 to 24 months after the boles of the trees have been sprayed to saturation from ground level to a height of 5 feet with 150 parts per million of cycloheximide in fuel oil. This mixture also shows promise as a foliage spray against blister rust. The use of systemics may bring revolutionary changes in control methods in the next decade or so. LESSENING THE THREAT OF INTERNATIONALLY DANGEROUS TREE DISEASES A. J. RIKER Professor of Plant Pathology and Forestry, University of Wisconsin, Madison, Wisconsin, U.S.A. The maintenance of sustained yields in high quality timber is one of the prime aims of research in forestry. Among the enemies of -|sustained yields are the following: fire, insects, animals, inroads of -|“civilization,’ and diseases. In the disease category one finds not | only the pathogenic agents that destroy foliage and kill trees, but also _| those that cause root, butt, and trunk rot. In the United States, the | total growth impact of forest diseases is estimated to be about 45 per- | i importance of injurious insects that might come from abroad also is _ clearly recognized. However, the insects are outside the scope of the | present consideration. __ Epidemic diseases are much more serious for forest trees than for comparable agricultural crops. If a field of wheat should be de- _ stroyed, something else could be planted the next year. But, if the _ trees are damaged, then 10, 25, or 50 years of the productivity of the land may be reduced or lost. Furthermore, with some of the root | and butt rot organisms another danger appears. Such pathogens may | develop in an apparently innocuous way in the nurseries. Thus, dan- gerous disease organisms may be distributed with the nursery stock used for reforestation throughout the areas. A program has been initiated to investigate (1) what the chances are that certain internationally dangerous diseases might be moved from one country to another, (2) how this movement could be pre- _ vented, or at least slowed down, (3) how quarantines could be made _ more effective, (4) how eradication might be accomplished if a foreign disease should appear, (5) how its damaging effects might be avoided or reduced if it appeared and could not be eradicated, and (6) how research might supply badly needed information about the host, the pathogen, and disease development. To facilitate such a program, the writer visited sixteen different countries to consult with leading for- esters, quarantine officials, forest geneticists, and pathologists. His trin was financed by the University of Wisconsin. Numerous suggestions on what to do have come from many compe- tent people. A summary appears below: Directory of Critical Tree Diseases.—In order to have available information about the epidemic diseases and their importance in each country, annotated lists of them have been, or are being, prepared in 119 120 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939. a number of places. From such lists, distribution maps can be made, ji At the same time, the maps may show the distribution of reporting 14 te pathologists rather than that of the disease. Negative reports may | | be significant only if a qualified person has made a diligent search, |} Such lists may not disclose diseases which appear innocuous in || t one country but which might be dangerous in others (such as the chest- || fl nut blight in east Asia). However, research, as discussed later, may || bring these to light. An example of such an annotated list is given | |i for the United States by Spaulding in USDA Agricultural Handbook || 4 No. 189 where 33 diseases come under the heading “American Forest | Diseases Potentially Dangerous to Forests of Foreign Countries.” _ Much can be learned by a study of surviving exotic trees in planta- ||# tions already made, as Spaulding has done. 5 | List of Key Men in Each Country.—A list is being prepared of © one or more men from each country active in forest pathology. These -|! men will exchange critical information, arrange for research on an | international basis between suitable individuals, and advise in case of | an outbreak. | Strengthening Quarantines.—Plant quarantines are the accepted |): bulwark against the entry of dangerous tree diseases into a country. | Modern air travel greatly increases the chances for distributing patho- — gens from one country to another. Many foresters are concerned about the effectiveness of quarantines because, no matter how well they are — | administered, dangerous pathogens may get through. Forest patholo- gists have an obligation to supply to quarantine officials a list of the most dangerous pathogens and to describe the diagnostic symptoms by which they may be recognized. At the same time interferences with commerce, travel, and the exchange of scientific materials need to be held to a minimum compatible with protection. More research is _ needed if quarantines are to achieve maximum dependability. 5 | Organizations Now Operating.—Various organizations deal in one way or another with certain aspects of these foreign tree disease — problems. The names of some important ones follow: European and Mediterranean Plant Protection Organization; Moscow-Peking Con- vention; Plant Protection Committee for the South East Asia and Pacific Region; Inter-Africa Phytosanitary Commission; Organismo International Regional de Sanidad Agropecuaria (Central America) 5 Plant Quarantine Division, ARS, U.S. Department of Agriculture; and Division of Plant Protection, Canada Department of Agriculture. In addition. the Food and Agriculture Organization of the United Nations in Rome is interested in reducing the spread of forest patho- gens from one continent to another and can supply the name and ~ address of the quarantine services in all member countries. Cooperative International Research.—For a number of critical — problems no one knows the answers. To secure them, cooperative re- search is essential between men in different countries. Obviously, one — cannot move either the pathogens or the living trees that might carry ~ them from one country to another except with extensive precautions. However, disease-free selected or treated seed can go from one country to a suitable place in another country with relatively little danger. — Some important topics for research follow: I (a) Host ranges. The different kinds of trees attacked by critical — pathogens need exploration. In some cases related ornamentals carry — | DANGEROUS INTERNATIONAL FOREST TREE DISEASES 121 tree diseases. Such research may best be done in nature at a location where the pathogen is active. (b) Alternate hosts. Especially with the rusts (e.g., white pine blister rust has one critical stage on currants and gooseberries) the various plants necessary for the development of certain stages of the fungus need to be characterized with precision. (c) Environmental influences. Temperature, moisture, light, and mineral nutrition have imnortant influences favoring or discouraging epidemics. The study of microclimate is essential for knowing how the pathogens work and how their damage may be prevented. (d) Disseminating agents. The potentialities of different carriers of pathogens need investigation, especially insect vectors. (e) Seemingly innocuous pathogens. Attempts should be made to disclose dangerous pathogens that are seemingly unimportant in their native country. Chestnut blight was considered of no consequence in east Asia, but when the pathogen reached America, it practically eliminated the American chestnuts. Suitable experimental plantings might disclose such wolves-in- sheep’s-clothing. (The technique for such research might follow the work done with the world collection of wheat). (f) Improved methods for eradication. If a dangerous disease should appear in a limited area of a country, eradication might be tried. Fire and chemicals have been useful, but certain other proce- dures also may be valuable. To be most effective, a technique for eradication should be developed in the country where the disease is active. The results should be available for immediate use to coun- tries where the disease might appear as a new invader. (g) Disease resistance. In many countries native trees fail to meet the needs for reforestation or afforestation. Trees from other coun- tries have been widely and advantageously used, but sometimes with disastrous results from disease. Furthermore, tree breeders are con- tinually developing improved trees. In both cases tests for resistance to dangerous diseases are essential. The selection and development of disease resistant trees hold great promise. For many kinds of research involving pathogens and isolation, sev- eral locations are needed. An island with a mountain might provide many desirable conditions. Changes in moisture occur from the rainy to the dry side. Changes in temperature appear at higher or lower elevations. In some mountain valleys the length-of-day would be shortened. In such isolated places pathogens might be studied effec- tively with little danger of spreading the diseases. Relations with Agricultural Research Stations.—In many coun- tries the forest pathologist works in relative isolation from men trained and experienced in handling various field, forage, fruit, fiber, and plantation-crop diseases. Such men usually have a background of information and “know-how” as well as equipment that the forest pathologist could use with advantage. For the most part, all this would be available merely for the asking. Active cooperation be- tween forest pathologists and agricultural pathologists deserves not only encouragement but also the active removal of any physical and administrative barriers that prevent their working together. In conclusion, the possibilities are dismaying that internationally dangerous tree diseases may move from one country to another and upset sustained yields. However, international understanding, co- 122 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 operation, and research can do much to slow down or even to prevent more catastrophes like that caused by chestnut blight in America, Summary 1. A directory of critical diseases in each country is needed. For example, in the United States Spaulding lists 33 diseases potentially dangerous for other countries (USDA Handbook No. 139). 2. A list of key men is essential. At least one man per country should assemble and distribute information. 3. Strengthening quarantines 1s imperative, but interference with commerce should be minimal. 4. Hxisting organizations are adequate. 5. International researches essential for effective operations in- clude: (a) improved methods for diagnosing diseases and the prepara- tion of authoritative host ranges of dangerous fungi; (b) under- standing of alternate hosts of rusts; (c) the critical importance of environment (e.g., temperature, moisture, light, and mineral nutri- tion), of seasonal development, and of microclimate to epidemic out- breaks; (d) the characterization of agents disseminating pathogens, especially insects; (e) the unmasking of seemingly innocuous patho- gens (e.g., chestnut blight) by suitable foreign plantings; (f) im- proved eradication procedures to be developed where the diseases are rampant; and (g) the development of elite and resistant varieties. 6. Improved cooperation between agricultural experiment stations and forestry research stations would be mutually beneficial. DISCUSSION AND RECOMMENDATIONS There was general concurrence with Professor Riker’s appraisal — of the need for international cooperation to lessen the intercontinental spread of forest pathogens and with his suggestions for future ac- tions to that end. The Working Group agreed unanimously to this plan of action: 1. To stimulate the preparation of annotated lists of dangerous forest diseases in all continents. 2. To draft a roster of leading pathologists in all continents to whom may be sent inquiries about local forest diseases and information on threatening diseases. 3. To advise existing plant quarantine organizations of the potential hazard of forest diseases in other countries and con- tinents. 4. To emphasize the need for increased research on forest dis- ease prevention and control in all continents. The Working Group approved a proposal that an international symposium should be organized to consider the particularly danger- ous forest diseases of all continents and to recommend measures to lessen or prevent their intercontinental spread. It was also recom- mended that the Union should be requested to ask FAO to sponsor such a symposium at an appropriate time and place. The Working Group will assume all responsibilities for arranging for the tech- nical subject matter coverage at the symposium. U.S. GOVERNMENT PRINTING OFFICE; 1963 O—687-137