510 Report op the Mycologist op the 



the time of planting seems to make no difference. Neither is it 

 to a great extent dependent upon weather conditions. It was 

 plentiful in Dutchess county in 1894 which was there a very dry 

 season; it was still more plentiful in 1895, a moderately wet sea- 

 son; and it also appeared on Long Island in very wet weather. 

 Sometimes one o^r two stalks in a hill will be diseased while the 

 I'emaining stalks continue healthy and mature their tubers. The 

 yield is diminished and the tubers arc poor in quality. Probably 

 they are considerably injured for seed purposes. 



There are several wilt diseases of the potato known and it is 

 possible tliat tbis is one which has already been reported but I 

 think not. I know of no description of a potato disease in which 

 mention is made of a coloration of the young leaves correlated 

 with a blackening of the fibro-vascular bundles at the stem end 

 of the tubers; and a description of this disease which omits these 

 characters is very incomplete because they are constant and the 

 most striking characters of the disease. 



The damage is not done by insects. It seems to be a clear case 

 of strangulation caused by the attacks of some fungus just be- 

 neath the surface of the soil. Thediseased stems contain an 

 abundance of fungus mycelium but I have not been able to deter- 

 mine what particular fungus is the cause of the trouble. I 

 strongly suspe(;t that the damage is done by Oospora rosea* 

 (Preuss) Sacc. & Vogel, which may nearly always be found on 

 the insid(,' of diseased stems after the death of the plants. 

 Melanospora onidta^' Zukal, supposed to be strictly saprophytic, 

 is also fre(]U('nt]y foiuid on the inside of dead diseased stems; but 

 I have been unable to find any specimen of the Termiculana 

 which Dr. Halstedf fouud in connection with his stem-blight of 

 potatoes in New Jersey. 



The disease will l»c a difficult one to treat. It cannot be con- 

 trolled liy sjiraying. 



• Dftermlned hv T)r R. Tliaxter. 



+ Halste-I. B !> . N>'w J.'rs°v Aprrl. Expt-rimo"! s",;i,:ii. Ix'^port f .r isoi, p. 354. 



