LIST OF DISEASES OF ECONOMIC PLANTS 3 



In some of the host genera, as, for example, Quercus, it has been 

 impracticable to list the diseases for each species separately. In 

 many genera, such as Prunus and Rubus, in which many of the records 

 of our collaborators simply report a disease as occurring-" on Prunus " 

 or "on raspberry," it is not possible to give the particular species 

 of the host; and in some genera the nomenclature of the species is so 

 confused that it is almost impossible to determine what host the 

 collaborator had in mind unless the authority for the species is given 

 or a specimen supplied. For example, the name Populus balsamifera 

 is sometimes applied to any one of a number of species of Populus. 

 In some of the records the generic name of the host species only is 

 given. In this connection it is desirable to urge upon collaborators 

 the great importance of giving specific names of the host plants when 

 •sending reports and specimens, or accompanying the reports by speci- 

 mens of the host as well as the fungus. This is essential in order that 

 our records may be as complete and accurate as possible. The 

 abbreviation "spp." after the generic name of a host means that all 

 diseases reported on any species of the genus are listed and con- 

 sidered in recording the distribution of the diseases — for example, 

 Salix spp. "Sp." after the generic name indicates that the diseases 

 listed were reported largely on an undetermined or doubtfully de- 

 termined species of the genus— for example, Begonia sp. 



In certain host genera the diseases are listed separately for one or 

 more of the common or important species, following which the dis- 

 eases of all other species of the genus are grouped under "sp." or 

 "spp." In such cases the diseases and their distribution do not 

 necessarily include the diseases or distribution as listed under specific 

 host species — for example, Juniperus virginiana and Juniperus spp*. 



NAMES OF PATHOGENS 



As there is no general agreement at present among the mycologists 

 and phytopathologists of the world in regard to the names of fungous 

 parasites, it has been found necessary to adopt for the purposes of 

 this list, as a rule, the names which are at present in most general 

 use. For some large groups of parasitic fungi, of which more or less 

 recent monographs are available and are largely used for reference 

 by pathologists, it has seemed best to follow rather closely the 

 nomenclature of such works. 



Rusts. — The specific names of the rusts which appear in Volume 

 VII of North American Flora have been adopted, except in a few 

 cases where long usage has established a name so firmly that there 

 seems to be no good reason for attempting to supplant it by another; 

 for example, Puccinia graminis is used instead of P. poculiformis 

 for the stem-rust of wheat and P. coronata instead of P. rliamni for 

 the crown-rust of oats. Generic names of long standing and in 

 general use, such as Puccinia and Uromyces, are also retained. 



Smuts. — The names in this group are those of Clinton's mono- 

 graph on the Ustilaginales in Volume VII of North American Flora. 



Powdery mildews. — Salmon's monograph on the Erysiphacese in 

 Volume 9 of the Memoirs of the Torrey Botanical Club has been 

 followed in this group. 



Downy mildews— The papers of G. W. Wilson on the Peronos- 

 porales have been followed with the exception of the generic name 



