1021.] FROGHOPPER BLIGHT IN TRINIDAD. 61 



Soil. An outline is given of the chief types of soil which are found 

 in the sugar districts of Trinidad. Tliese soils are more uniform in tlxe 

 north and more confused and irregular in the south. Correspondingly 

 we find the blight more uniformly widespread over large areas in the 

 Northern districts and more irregular and patch}' in the Southern 

 districts. 



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

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

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

 correspond to patches of heavier poorer soil. A diagram shows a very 

 striking instance of the way in which the damaged fields on one estate 

 have been confined to the red soil areas. 



Chemical analysis of a number of soils of damaged and undamaged 

 fields show that the undamaged fields are, on an average, alkaline or 

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

 iiumus. The damaged fields are neutral or acid with a lower per- 

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

 relative amount of SO.^. 



Drainage has considerable influence on the prevalence of bliglit, 

 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 betv/een the unimproved part 

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

 damaged. 



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 tlie quantity 

 available. Sheep manure from Venezuela and lagoon nuid from the 

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

 considerably improved and suffer less from blight. 



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 that this manure should not be used continuously on soils deficient 

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

 i))tervals by heavy applications of lime. 



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

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

 attache 1 than ratoon canes. Second ratoons are usually more damaged 

 than first ratoons. 



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

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

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

 may take place. 



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

 crop is very undesn-able 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 \\!iatever 

 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 

 ■)f danger to the surrounding fields. 



