196 MAINE AGRICULTURAL EXPERIMENT STATION. I914. 



in new ground. Less favorable results were obtained with formalde- 

 hyde, and neither coating the seed with sulphur nor applying lime to 

 the soil at the rate of 3,000 pounds per acre produced any apparent 

 beneficial effect. 



About the same time that Rolfs was working on the Rhizoctonia dis- 

 ease of the potato in Colorado, Selby (13) was making similar studies 

 in Ohio. Selby was attracted by certain above-ground signs of disease 

 of potato plants in various parts of that state. He states that for at 

 leasit 3 years previous to the publication of his paper complaints had 

 been received of the early dying of potato plants, apparently from some 

 disease below ground, before the formation of many tubers. A promi- 

 nent characteristic of the affected plants was an excessive branching 

 and in general a conspicuous clustering of these branches or of the 

 terminal leaf groups. This condition or appearance he designated as 

 "Potato Rosette." While recognizing that other below ground injuries 

 of the stem might produce similar effects on the tops he was satisfied 

 that the rosette appearance of the foliage was associated with or a sec- 

 ondary effect of the attacks of the Rhizoctonia fungus on the parts of 

 the plants below ground similar to those described by Rolfs. 



Selby also carried on experiments to test seed disinfection as a means 

 of preventing the disease. These, apparently conducted on a smaller 

 scale, gave quite different results from those obtained by Rolfs with 

 regard to the relative efficiency of corrosive sublimate and formalde- 

 hyde as is indicated by the following quotation :* 



"The warranted conclusion, drawn from the tests of two seasons with 

 formalin and the extended work of many seasons at the Station with 

 corrosive sublimate seed treatment appears to be that the corrosive 

 sublimate seed treatment does not prevent the rhizoctonia disease to 

 any appreciable extent, while the formalin seed treatment, as shown 

 conspicuously by the study of the growing plants and usually in the 

 yields of tubers, does prevent the disease to a very marked extent." 



Clinton (3) in 1904 mentions the occurrence of the fungus on potatoes 

 in Connecticut. After examining several potato fields he says : "Appar- 

 ently the plants did not suffer so severely from the fungus as some 

 writers claim elsewhere. However, the relative injury caused here by 

 the fungus is a subject which needs further attention, since the parts 

 attacked occurring under ground the injury and cause may easily escape 

 notice." 



Orton (9) in 1909 states that Rhizoctonia causes a stem blight of 

 potatoes and a surface cracking or russeting of the tubers in heavy 

 western soils, particularly San Joaquin County, California. 



Giissow, the Dominion Botanist of Canada, in his report of 1912 (8) 

 gives a summary of the important characteristics of the Rhizoctonia 

 disease of the potato but does not state where or to what extent it 

 occurs in Canada, in conversation with the senior writer after the above 

 was written Prof. Giissow stated that the disease is common in various 



* p. 58. 



