1915] 



DUGOAR RHIZOCTONIA CROCORUM AND R. SOLANI 431 



nomena may be so striking in appearance as to dominate the 

 primary injuries or lesions. 



For convenience we may arrange the types of disease in the 

 following categories: (1) damping off, (2) stem rot, (3) root 

 rot, (4) leaf rot, (5) scab, and (6) such secondary effects as 

 rosette, little potato, and leaf roll. Since more than one type 

 of disease may occur upon a single host, and especially since 

 one form of the disease may grade into another, it will be more 

 practicable to discuss these under the following captions: 

 (1) damping off, (2) potato diseases, (3) rot of fleshy roots, 

 (4) stem and root rots of herbaceous plants, and (5) fruit 

 and leaf injuries. 



DAMPING OFF 



It would appear that the first mention of a disease of seed- 

 lings caused by Rhizoctonia is that of beets, recorded 

 Eidam ('87), although he gives no complete account of the 

 evidence. It is preferable to date our knowledge of damping 

 off diseases caused by Rhizoctonia from the work of Atkinson 

 ('92), who studied particularly sore shin of cotton, but he 

 also found the "sterile" fungus to cause damping off 

 of seedling beets, radish, lettuce, Qgg plants, cabbage, and 

 other plants in the forcing house. The later identification 

 of the fungus concerned (Duggar, '99) and its association 

 with the damping off of various plants (Duggar and Stewart, 

 '01 ) was only the beginning of the observations which have 

 now served to direct our attention to the vast importance of 

 this fungous disease throughout the United States both in the 

 greenhouse and in the outside seed bed. 



Among numerous instances in which damping off has been 

 reported due (or in all probability due) to this fungus may be 

 noted the following: (1). It has been found as a source of 

 serious injury to ginseng in the seed bed (Van Hook, '04; 

 Whetzel and Rosenbaum, '12). (2). Tobacco seedlings are 



so frequently injured that soil treatment has received special 

 consideration in the case of this crop (Selby, '04; Cook and 

 Home, '05). (3). As a damping off disease of cotton (sore 

 shin) it occurs not only in America but in Africa (Balls, '05, 

 '06) and possibly in India (Shaw, '13) as well. (4). Tomato 



