INSTITUTE AND COLLEGE, PUSA, FOR 1911-12. 67 



was of interest as it proved to be identical with that known 

 in Egypt as " sore shin " and in America as " damping off," 

 both of w^hich diseases were attri})iited by their investigators 

 to an unnamed sterile fungus. 



Special attention was paid to the possibility of the exist- 

 ence of biologic forms within the morphological species 

 R. Solani. It was found that the race on jute was markedly 

 different in its infective power from the fungus on cowpea, 

 groundnut and cotton. The former would only infect its 

 own host whereas the fungus upon either of the other three 

 hosts could infect any one of the remainder. 



A second species of Rhizoctcmia, possessing much larger 

 sclerotia, was found on groundnut and cowpea. It soon 

 became clear that great confusion existed in the published 

 literature between these two forms, which have been attri- 

 buted to a single species under the name Rhizoctonia 

 violacea Tul. The second form also occurs sometimes on 

 potato, where it has been identified by American writers 

 as R. Solani and stated to have a Basidiomycete, Corticium 

 v>agum, as its perfect stage. The investigations of the last 

 year have confirmed the latter point but have shown that 

 the fungus associated with Corticium vagum is a distinct 

 and separate species. It is suggested that the name 

 R. violacea may be retained for this form. 



The fact that Rhizoctonia may live in the soil of an 

 infected field for years renders the disease a peculiarly 

 difhcult one to combat. In Egypt a dressing of naphthalene 

 has been found very beneficial in the case of cotton, while 

 in England a weak solution of carbolic acid applied to the 

 soil has given good results. The latter method is, however, 

 too expensive for general use. It is fortunate that, so far, 

 cereal crops appear to be immune to this disease and a 

 careful rotation of crops is probably the best method of 

 lessening its ravages. 



(c) Wheat rust. — Last year was marked by a severe 

 attack of wheat rust, the first for a number of years, in the 

 Central Provinces. The disease was also prevalent in some 



