220 Report of the Department of Botany of the 



he attributed to Rhizoctonia), believes the formalin more effective 

 than the corrosive sublimate bath. He has noted the yields of the 

 treated and untreated tubers and used the appearance of the foliage 

 as a criterion in determining the effectiveness of the treatment. 

 He states, " the warranted conclusion, drawn from tests of two 

 seasons (1901 and 1902) with formalin and the extended work of 

 many seasons at the Station with corrosive sublimate appears to be 

 that corrosive sublimate seed treatment does not prevent the 

 Rhizoctonia disease to any appreciable extent, while the formalin 

 seed treatment, as shown conspicuously by study of the growing 

 plants and usually in the yields of tubers, does prevent the disease 

 to a very marked extent." In Selby's second report 12 of his in- 

 vestigations on the treatment of Rhizoctonia, there are recorded 

 experiments in which treated and untreated tubers were planted 

 in infected soil as well as in soil in which the disease was not supposed 

 to be present. The Carman variety is the only one that received 

 treatment with the standard substances and was planted in infected 

 soil and grown apparently under similar conditions. He used 

 formalin at the rate of one pound (pint) to 30 gallons of water, 

 immersing the tubers for two hours. It is uncertain what strength 

 of mercury bichloride solution was used for he states, " the usual 

 strength of one ounce to 16 gallons of water was employed," and 

 in this solution the tubers remained for one hour. However, this 

 is one-half the strength used by Bolley 13 who recommends one 

 ounce to 1\ gallons of water, and an immersion for \\ hours. The 

 average yields from the check, formalin, and corrosive sublimate 

 treated plots are calculated at 139.9, 131.4, and 127.1 bushels per 

 acre, and the percentages of harvested tubers showing Rhizoctonia 

 are 62, 46, and 29.5 per ct., respectively. The yields from the 

 treated tubers are slightly smaller than those from the untreated, 

 but the least percentage of Rhizoctonia is found on the product of 

 tubers treated with mercury bichloride solution. 



Selby also treated Rhizoctonia-infested tubers with formaldehyde 

 solution for various periods of time. The Early Trumbull variety 

 was immersed in standard formalin solution for 2, 3|, and 4| hours 

 and planted in infected soil under apparently similar conditions. 

 The check plots showed 94 per ct. of the harvested tubers infected 

 with Rhizoctonia, while the tubers treated for 2, 3f , and 4£ hours 



n Loc. cit. 

 n Loc. cit. 



