- INSTITUTE, PUSA, FOR 1919-20 59 



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III. Diseases of Plants. 



(1) Black band disease of jute. The research work 

 on this disease was continued by Dr. Shaw. In Bihar, in 

 1919, the state of the jute crop was similar to that in 1918. 

 A considerable portion of the seed-crop had, however, been 

 sown as late as June and this was invariably clean and 

 healthy. This confirms the observations made last year 

 from the infection" of the crop all over Bihar that the late 

 sown crop is relatively immune. In the more early sown 

 areas the crop was only slightly diseased and not to an ex- 

 tent which would seriously diminish the yield. The condi- 

 tion of the crop on the Dacca Farm by no means agreed 

 with that in the previous season. Both the green and the 

 red-stemmed varieties of Cor chorus olitorius were attacked. 

 The incidence of the disease was not heavy and varied 

 considerably in different fields on the farm. The greatest 

 damage seen in any one area was probably about ten per 

 cent. The red-stemmed C. capsularis was also attacked. 

 These observations are quite sufficient to show that neither 

 the red-stemmed varieties of C. capsularis nor of C. oli- 

 torius were resistant to the disease. At Chinsurah Farm 

 where the jute consisted of the same red and green varieties 

 as at Dacca, the crop was very fine, averaging about 14 feet 

 in height, and there was not a single case of black band. 

 At Rangpur the crops of both C. olitorius and C. capsularis 

 were infected. The disease, however, only reached an ap- 

 preciable degree when the plants were of a certain size. 



Infection experiments carried out both on plants in 

 pots and on plants in the field showed that though red 

 varieties of C. capsularis and C. olitorius are by no means 

 immune yet under the conditions of the experiments they 

 seem less susceptible. A large number of experiments car- 

 ried out on green C. capsularis showed that the number of 

 successful infections depended on the humidity of the air 

 at the time of experiment and the exact determination of 

 the conditions is a point for further investigation. 



The field experiments carried out in 1918 with the object 

 of throwing light on the conditions affecting the spread of 

 the disease were repeated. 



