1915] 



DUGGAR RHIZOCTONIA CROCORUM AND R. SOLANI 445 



Sorauer, Berlin, 1900 ; from Prof. Magnus, Berlin, 1901 ; from 

 Prof. Delacroix, Paris, 1901; and material secured on the 

 markets of various cities, 1905-06. 



As far as the writer has been able to determine, the fol- 

 lowing synonomy may be listed for Corticium vagum B. & C. : 



Rhizoctonia Solani Kiihn (1858). 

 Rhizoctonia Betae Eidam [non Kiihn] (1887). 

 Rhizoctonia Napaeae West. (1846). 

 Rhizoctonia Rapae West. (1852). 

 Hypochnus Solani Prill. & Del. (1891). 



PREVENTION AND CONTROL 



Much the same situation confronts us regarding the pre- 

 vention and control of Rhizoctonia Solani as in the case of 

 R. Crocorum. The presence of the fungus in practically all 

 soils serves to emphasize the importance of cultural methods 

 including drainage and sanitation. In this case, however, 

 since the fungus is of so much importance in the seed bed and 

 in the greenhouse special preventive measures may be prac- 

 tised. Selby ( '06) found that the treatment of the seed bed 

 with formalin (1:160 to 1:200) proved satisfactory in most 

 cases. In general, the best results have been obtained by 

 steam sterilization, and where the facilities are at hand it is 

 practicable to apply this to any type of greenhouse work, and, 

 in certain cases, to seed beds outside. Liming has been recom- 

 mended for the control of the disease in the field, but this has 

 not been uniformly successful, and cultural studies have 

 shown that the fungus is able to withstand a high percentage 

 of alkalinity. Nevertheless, when liming results in the im- 

 provement of physical and sanitary conditions of the soil it 

 undoubtedly assists in restraining the activity of the fungus 

 in an indirect way, possibly by raising the resistance of the 



host. 



Even though the fungus may be widely distributed, it is 

 advantageous to plant clean "seed." This applies particu- 

 larly to the case of the potato. The presence of the sclerotia 

 upon the tuber makes possible the early spread of the fungus 



