JOMALOFAGEICDITIALISEARCB 



DEPARTMENT OF AGRICULTURE 



Vol. VI Washington, D. C, June 5, 1916 No. 10 



SILVER-SCURF OF THE IRISH POTATO CAUSED BY 

 SPONDYLOCLADIUM ATROVIRENS 



By Eugene S. Schultz,^ 



Expert in Potato Investigations, Cotton and Truck Disease Investigations, 



Bureau of Plant Industry 



INTRODUCTION 



Silver-scurf of the Irish potato (Solanum tuberosum) , caused by Spon- 

 dylocladium atrovirens, has been known in Europe since 1871, when it 

 was discovered by Harz (6) on new potatoes in Vienna; but there is no 

 record of its appearance in this country until mentioned by Clinton (4) in 

 1908. Notwithstanding its comparatively recent discovery, its general 

 distribution in the eastern United States was shown by Melhus (7), 1913, 

 who also raised the question as to its importance as a new potato disease 

 in America, while its appearance in the Northwest was first reported in 

 1914 by Bailey (2) and later, in 1915, by O'Gara (8). 



Reports of studies made by former investigators contain contradictory 

 assertions, especially on the effect of this organism upon the host. It is 

 evident, therefore, that further study of the symptoms, manner of infec- 

 tion, and physiology of the organism is desirable in order to understand 

 more fully the significance of this disease, which has already become 

 widely distributed in this country. 



STUDIES OF THE FUNGUS 

 MORPHOLOGY 



Spondylocladium atrovirens, one of the black molds, is classified accord- 

 ing to Saccardo (9, p. 483) in the Fungi Imperfecti under the Dematieae. 

 The genus Spondylocladium is characterized by its dark multiseptate 

 conidiophores, which bear the many-celled conidia pleurogenously in the 

 form of whorls. 



Conidiophore and conidia formation can be studied either in hanging- 

 drop or agar cultures. When the organism was cultured on agar plates 



1 The sincere thanks of the author are due to Dr. I.E. Melhus, Bureau of Plant Industry, for many help- 

 ful suggestions during the progress of this study and the preparation of the manuscript, and also to Prof. 

 L. R. Jones, of the University of Wisconsin, in whose laboratory a part of the work was conducted. 



Journal of Agricultural Research, Vol. VI, No. lo 



Dept. of Agriculture, Washington, D. C. June 5, 1916 



dy G— 81 



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