80 Bulletin 186. 



That Rhizoctonia is the cause of this carnation stem-rot has ?jeen 

 proven conclusively by inoculation experiments with pure cultures 

 repeated many times. Fig. 23 is from a photograph of a carnation 

 plant killed by artificial inoculation with a pure culture of Rhizoc- 

 tonia. It presents the symptoms typical of the Rhizoctonia stem- 

 rot disease. 



This stem-rot* is one of the most troublesome of the carnation 

 diseases and probably occurs throughout the whole United States 

 wherever the carnation is grown. Frequently entire houses of 

 mature plants are destroyed by it. During the past autumn it 

 appears to have been unusually prevalent. It attacks plants of all 

 ages both in the field and in the greenhouse, and is one of the prin- 

 cipal causes of the damping off of carnation cuttings. In green- 

 house benches it spreads slowly through the soil from one plant to 

 another ; but according to our experiments never through the air, 

 as from one bench to another. Its principal mode of dissemination 

 is by means of affected plants and cuttings. 



On the Sweet William, Dlanthus hai'hatus. 



Since Rldzoctonia is an active parasite on the carnation, it is to 

 be expected tliat it attacks the closely related Dianthus harhatuSy 

 and such appears to be actually the case. 



November 5, 1900, we had the privilege of examining a badly 

 diseased plat of about 1,600 plants of Dianthus harljatus at Queens, 

 Long Island. In the course of the season about 90 per cent of 

 these plants had died from a sort of stem-rot. Several of the dead 

 plants were not completely dry at the time of our visit, so it was 

 possible to get some idea of the nature of the disease and its cause. 

 The symptoms were strikingly like those of the Rhizoctonia stem- 

 rot of carnations. The leaves had a sickly, yellowisli color and 

 were perfectly limp. The main stem and its numerous branches 

 were soft-rotten at the surface of the soil, so that when an attempt 

 was made to ^\\\\ an affected plant it broke off readily at that point, 



* There is a somewhat similar and destructive Fasariam stem-rot of carna- 

 tions. See Sturgis, W. C. Twenty-first Ann. licp. Conn. Agr. Exp. Sta. (1897): 

 175-181; Prillieux et Delacroix, Comiit. Rend, de 1' Acad. Science, 129: 744- 

 745; and Stewart, F. C. Bot. Gaz., 27: 129-130. 



