16 TBIXIDAD AND TOBAGO BULLETIN. \XIX. i. 



countries, and is supported h\ tlie experimental evidence so far as it 

 goes, though more of tliis is to be desired. The nature and characteris- 

 tics of root disease of this type were somewhat fully discussed in last 

 year's report. The point to be made in the present connexion is that 

 the canes grown under its influence are typically stunted, with short 

 joints, being thus very different from the weak and thin but rather long- 

 jointed canes resulting from infestation with froghopper. 



24. Root Disease : Tijjye B. A more acute and definite form of 

 root disease is produced when the fungus invades the lower joints of the 

 stems. A field examined early in November and kept under 

 observation later provided the best example of this type the writer has 

 met with. It is situated on level ground in an open valley, the soil a 

 fairly heavy brown loam in general but lighter on one margin. The 

 crop consists of first ratoons of Hill Nos. 6 and 12. The soil gave 

 evidence of being well worked and the drainage system appeared efficient. 

 Pen manure had been applied to the plant canes, and suljjhate of 

 ammonia 2 cwt. to the acre in two applications to the present ratoons.. 

 The crop was well developed, its appearance suggesting that of good 

 plant canes, and the indications were that the onset of the disease had: 

 been sudden and recent. There was comparatively little evidence of the 

 presence of froghoppers. All the stools were exceedingly loose, and 

 easy to push over ; many of the canes were half-uprooted with their 

 own weight. Very many large canes exhibited the basal joints in various 

 stages of becoming reddened, shrunken, full of mycelium, dying and dead ; 

 the remaining joints continuing in sound condition until the severance 

 of connexion with the root system took effect. The young shoots 

 were dying upwards from infestation in the base, not downwards as 

 in froghopper blight. A Marasmius species, with white caps up to 

 half an inch in diameter and violet-black stallis, was fruiting abundantly 

 from roots, root eyes, young shoots and basal joints. 



25. No defect in the conditions which could be held responsible for 

 this outbreak was visible to inspection. About the only feature that 

 suggests a possibility of an explanation is that the reaction of the dressing 

 of sulphate of ammonia may have brought about extreme depletion in 

 some soil constituent, most probably lime, already near the minimum. 



26. A similar infestation on a smaller scale was seen later forming a 

 blighted patch in ratoons of B 156. The writer has on occasion met with 

 disease of the same type on plant cane in Barb:idos, the fructifications 

 there developed being referable to Marasmius Sacchari. 



THE DISTRIBUTION OF FROGHOPPER BLIGHT IN 1919. 



27. The third brood infestations of 1919 have been desciibed as 

 follows in the summary already issued. They represent a situation 

 near the minimum of froghopper prevalence : — • 



(a.) A belt of infestation in the Naparimas which coincides closely 



with the occurrence, in bands and patches, of a particular type 



of red clay. 

 (b.) An area of several acres in the Northern sugar dastrict, in 



which the soil, a fine silt, is closelj' compacted and 



probably sour. 



