60 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



they are not liable to contamination and they will escape 

 disease in the plains, since the plains' crop is normally free 

 and local infection not usually to be feared. The outbreaks 

 investigated showed that the seed used was probably infec- 

 ted, that it was brought from the Hills when the tempera- 

 ture below was under the normal for sowing time, and that 

 the crop was exposed to rain or ground fogs as it ripened. 

 Unless all these conditions are met, the crop may be ex- 

 pected to escape in the plains and in most of peninsular 

 India. 



(4) Rhizoctonia and other sclerotial diseases. A 



severe attack of Rhizoctonia on jute in the experimental 

 plots on the Dacca Farm enabled the interesting observa- 

 tion to be made, in July, 1916, that plots which had received 

 heavy fertilization were practically immune. As the ex- 

 periment did not give any indication of the constituents 

 which led to this result, a new series was laid down by Mr. 

 Finlow, Fibre Expert to the Bengal Government, and in a 

 recent report this officer states that the results strongly 

 suggest that potash deficiency is the main cause of the seve- 

 rity of the disease on the old alluvium north of Dacca. The 

 enquiry is being followed up in connection with the accu- 

 mulating evidence that certain Indian soils are dangerously 

 deficient in one or other of the essential constituents of 

 plant-food, and that this deficiency may be manifested in 

 increased susceptibility of the crop to fungus diseases. 

 This point will be further referred to under " tikka " dis- 

 ease of groundnut. 



From time to time reports and specimens of a serious 

 root rot of cotton in northern and western India have been 

 received. A local investigation in the southern Punjab, 

 supplemented by a re-examination of the material in the 

 Pusa collections, revealed a certain definite train of symp- 

 toms, enabling the disease to be recognized with certainty. 

 Its cause is very obscure, several fungi being present on the 

 roots of most specimens, but none so extensively nor so 

 regularly as to be the probable cause. Two have been iso- 

 lated for further work, a Rhizoctonia and a sterile, non 



