146 JAMIESON AND WOLLENWEBER : FUSARIUM TRICHOTHECIOIDES 



PHYTOPATHOLOGY.—^ external dry rot of potato tubers 

 caused by Fusarium trichothecioides, Wollenw. C. O. Jamie- 

 son and H. W. Wollenweber, Bureau of Plant Industry. 

 Communicated by C. S. Scofield. 



Certain types of decay of potato tubers have been ascribed by 

 various authors to the action of the fungus Fusarium (Clinton, 

 1895; Smith and Swingle, 1904). Conclusive infection experi- 

 ments have been performed by several (Pizzigoni, 1896; Wehmer, 

 1897; Pethybridge and Bowers, 1908; Longman, 1909 and others). 1 

 In most cases Fusarium solani (Mart.), or a species thought to be 

 a synonym of it, is said to be the real cause of the rot. The differ- 

 ent kinds of decay described on the one hand, and the negative 

 results often secured on the other, directed attention to a more 

 complete study of the morphology of potato Fusaria and their 

 differentiation. During this study, which was done in Germany, 

 not less than fifteen species were isolated, of which nine have oeen 

 published (Appel and Wollenweber, 1910). As a result of recent 

 and as yet unpublished experiments at Dahlem-Berlin only two of 

 the nine species have been found to be wound parasites of the stored 

 tuber: F. coeruleum (Lib.); F. discolor var. sulphureum (Schlecht. 

 s. sp.). Closely related to the latter is a new species, found in the 

 United States and characterized by a peculiar injury known as 

 external dry rot. This disease has been studied by Miss Jamie- 

 son during the past two years. 



Attention was first called to the disease in February, 1910, in 

 potato tubers sent from Spokane, Washington. Since then we 

 have examined samples of similarly diseased tubers from the 

 same locality, as well as from Iowa, Minnesota, Nebraska,, and 

 South Dakota. Symptoms of this disease have been noticed in 

 the field at the time of harvesting potatoes, in one instance the 

 estimated infection being about 10 per cent of the crop, but it is 



1 See also Appel and Kreitz. Der derzeitige Stand unserer Kenntnisse von den 

 Kartoffelkrankheiten und ihrer Bekampfung. Mitt. a.d. Kais. Biol. Anst. f. 

 Land und Forstw., Heft 5, 1907. Berlin. (With lists of the more important 

 references up to 1907), and Pethybridge and Bowers. Dry Rot of the Potato 

 Tuber. The Economic Proceedings of the Dublin Society, vol. I, 14, 1908, p. 

 547-558. 1 Tab. 



