The Rhizoctonia Damping-Off of Conifers 



13 



directly. The greater rapidity of this method permitted more extensive 

 examinations than could otherwise have been made. The method was 

 frequently checked by similarly examining sections of healthy seedlings. 

 Such organisms as did occur on these plates were common saprophytes. 

 Direct microscopic examination of diseased tissues made at frequent 

 intervals also served as a check on the method of isolation here employed. 

 The results obtained from the Ithaca nursery are summarized in table 2 

 on the basis of fungi isolated from both untreated beds and those treated 

 with chemicals for controlling the disease. The seedlings, all of which 

 were red pine, were collected during the last three weeks of June, 1925. 



TABLE 2. Summary of Isolations from Diseased Seedlings at the Ithaca Nursery 



The data presented in table 2 indicate that Rhizoctonia and Pythium 

 were the two fungi most frequently isolated at the Ithaca nursery, while 

 Alternaria, Phoma, and Fusarium also were found associated with diseased 

 seedlings. It is interesting to note that the seedlings from the untreated 

 beds, and those treated with sulfuric acid and Germisan, respectively, 

 yielded a much higher percentage of Rhizoctonia than of Pythium, while 

 the reverse is true for those beds treated with other materials. Since the 

 beds were artificially infested with Rhizoctonia, it would seem likely that 

 under natural conditions Pythium would have been the most important 

 organism involved in these beds. 



During the season of 192(5, extensive isolations were made at the Keene 

 nursery from seedlings representing a large number of infection foci in 

 beds of austrian, mugho, red, and white pine, Colorado and norway spruce, 

 and oriental arborvitae. Collections were made from June 1 to August 2, 

 the majority, however, being made during the month of June. It is 



