]')H FRcoiiopri:)^ Bi^icirr of suCxAR-cane. 



A number of examples are given of the great influence of the soil. 

 The red soils in the Naparimas are always inore liable to damage than 

 the black soils. Badly damaged parts of the field are always found to 

 correspond to patches of heavier poorer soil. Fig. 29 shows a very 

 sti'iking instance of the way in which the damaged fields on one estate 

 have been confined to the red soil areas (p. 109). 



Chemical analysis of a number of soils of damaged and undamaged 

 fields show that the undamaged fields are, on an avera.ge, alkaline or 

 neutral in reaction, with a higher content of lime, carbon dioxide and 

 humus. The damaged fields were neutral or acid with a lower per- 

 centage of lime, carbon, dioxide and humus, and possibly a higher 

 relative amount of SOs (p. 110). 



Drainage has considerable influence on the prevalence of blight, 

 and in fields liable to damage the drainage should be improved wherever 

 possible. A field in which the drainage had been improved in one-half 

 showed a distinct line across the field between the unimproved part 

 that was distinctly blighted and the improved part that was much less 

 damaged (p. 113). 



Manuring. Pen manure is the most valuable natural manure in 

 use in Trinidad and its effect on the condition of the soil is so 

 beneficial that every effort should be made to increase the quantity 

 available. Sheep manure from Venezuela and lagoon mud from the 

 Oropuche Lagoon are also good, and fields treated with them are 

 •considerably improved and suffer less from blight (p. 114). 



Sulphate of Ammonia is the commonest artificial manure in use but 

 the acid conditions found in the soils most liable to blight emphasizes the 

 fact tKat this manure should not be used continuously on soils deficient 

 in lime (as are most Trinidad soils) without counteracting the effect at 

 intervals by heavy npplications of lime. (p. 114). 



The age of the Cane at the Time of the Attack has a very 

 important effect. Plant canes in their first year are much less frequently 

 attacked than ratoon canes. Second ratoons are usually worse damaged 

 than first ratoons. (p. 115). 



There is some evidence that the ensuing crop of ratoons in a field cut 

 earlier in the year is worse damaged than in a field cut later. The canes 

 are larger but a relatively greater increase in the number of froghoppers 

 may take place (p. 116). 



Eotation. The system of replanting a field immediately after the old 

 crop is very undesiralile from the point of view of disease and insect 

 control. Conditions are most suitable for the insects and diseases to 

 pass on from one crop to the next. Abandoning the land to whatever 

 grasses and bush may grow up is little better, as many insects, including 

 the froghopper, persist in the grass and the abandoned plot is a source 

 •of danger to the surrounding fields, (p. 117). 



Tillage. There is evidence that good cultivation, by loosening and 

 aerating the soil, not only improves the cane but actually reduces the 

 number of froghoppers present. Occasionally damage is reported follow- 

 ing immediately on the use of implements, particularly sub-soil ploughs, 

 but when one considers the time taken for the development of the 

 greatest injury, it is usually seen that the damage in these canes would 

 have appeared whether or not the implements had been used. (p. 118). 



Variety. No variety of cane is innnune, but a few are more resistant 

 than others. "Uba" and "Badilla" are the most resistant, but are unfor- 

 tunately not generally considered suitable for cultivation (p. J 19). 



