JOMAL OF AGEICOLTIALISEARCH 



DEPARTMENT OF AGRICULTURE 

 Vol. VI Washington, D. C, May 29, 191 6 No. 9 



A WESTERN FIELDROT OF THE IRISH POTATO TUBER 

 CAUSED BY FUSARIUM RADICICOLA 



By O. A. Pratt, ^^ 



Assistant Pathologist, Office of Cotton and Truck Disease Investigations, 



Bureau 0/ Plant Industry »,«rAMCAl. 



INTRODUCTION 



Tuber- rots of the Irish potato (Solanum tuberosum) which are common to 

 the arid^ West may be grouped into two classes: Storage- rots and field- 

 rots. This paper is concerned only with certain rots attacking the potato 

 tuber while growing in the field. From the tuber-rots under discussion, the 

 fungus Fusarium r adicicola WoWenw. was isolated. Carpenter ^ in 191 5 

 demonstrated that F. radicicola could, under laboratory conditions, 

 cause decays in potato tubers similar in every way to these rots. His 

 experiments, however, v/ere conducted wholly in the laboratories of the 

 Department of Agriculture, in Washington, D. C. It was therefore 

 thought practicable to present this paper, which gives the results of 

 experiments performed under field conditions in the irrigated West. 

 These experiments substantiate the results obtained by Carpenter and 

 further establish the relationship of F. radicicola to the field tuber-rots 

 under consideration. 



THE DISEASE 



Under the head of fieldrot are considered several types of decay occur- 

 ring in potato tubers while yet in the field — a stem-end rot, a lenticel 

 rot, and a rot proceeding from eye infections. Eye infections in the 

 field are not as common as stem-end and lenticel infections. These 

 types of rot are known as " stem-end rot," " field dryrot," or " blackrot." 

 The name "blackrot" best describes them, for the decayed tissues are 

 nearly black in color when the tubers are taken from the field. The rot may 

 be further described as a comparatively dry rot, dark to nearly black in 

 color, proceeding from the stem end, lenticels, and occasionally from 

 the eyes of the tuber. The decay is first recognized by the blackened, 

 sunken appearance of the stem end, or, in the case of lenticel and eye 



' The observations and experiments set forth in this paper were confined principally to southern Idaho. 

 ' Carpenter, C. W. Some potato tuber-rots caused by species of Fusarium. In Jour. Agr. Research, 

 V. s, no. 5, p. 183-210, pi. A-B (col), 14-19. 1915. 



Journal of Agricultural Research, Vol. VI, No. 9 



Dept. of Agriculture, Washington, D. C. May 29, 1916 



dni G — 80 



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