EXAMPLES OF WIDELY DISTRIBUTED FOREST 



DISEASES 



J. E. Haxsbrough 



Director, Division of Forest Disease Research, Forest Service, U.S. 



Department of Agriculture. Washington 25, D.C., U.S.A. 



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. Puecinia gramirtis 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: \V. 

 Worldwide. The pathogens and their distribution are : 



Distribution 

 Pathogen by Continents 



Agrobaeterium tumefaciens (Sm. & Town.) Conn W 



Armillaria mellea (Yahl.) Quel TV 



Ceratocystis ulmi (Buism.) Moreau As.. E., NA 



Coryneum cardinale Wag Af., Aus.. E., NA 



Cronartium ribwola Fisch As.. E., NA 



Diplodia pinea (Desm.) Kickx W 



Dothichiza populea Sacc. & Briard E., NA, SA 



Endothia parasitica (Murr.) Ander As., E.. NA 



Fomes annosus (Ft.) Cke As..E.. NA 



F. pini (Fr.) Karst As., &, NA 



Fusicladium saliciperdum (All. & Tub.) Tub E., NA 



Lophodermium pin-as tri (Ft.) Cbev As.. Aus.. E.. NA 



Phaeocryptopus gaumanni (Rhode) Petr E.. NA 



Physalospora miyabena Fuk As., E.. NA 



Phytophthora cinnamomi Rands As.. Aus.. NA 



Rhabdocline pseudotsugae Syd E.. NA 



Valsa Kunzei Fr As., E., NA 



Verticillium albo-atrum Rein. & Bert Af., Aus.. E.. NA 



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