1919.] INVESTIGATION OF FROGHOPPEE PEST, ,t-c. 63 



forcing development in this direction before due caution tias been 

 learned. Some cases of the occurrence of blight on estates which, in 

 general, are excellently managed were claimed to be due t3 injury 

 brought about in this way. 



26. It is probable that the opposite danger should also be taken into 

 account, though I did not actually see any instance of it : namely, the 

 damage to tilth that results from the reduction of the soil to a dusty 

 consistency hj over-cultivation in very dry weather. 



Climatic Conditions. 



27. One marked advantage which the cane growing districts of 

 Trinidad possess over those of the northern islands lies in the 

 humidity of the air. In the other islands lands which are subject 

 to conditions as favourable in this respect were put under orchard 

 crops when the sugar market was depressed, leaving, with unimportant 

 exceptions, only the drier places, or those with light soils, to sugar-cane. 



28. In those islands, of which Barbados may be quoted as an example, 

 the tendency to root disease is largely increased by shortage of moisture. 

 Hence arises the necessity for short rafcooning periods or none at all, 

 for rotation, for thorough and clean cultivation, for the conservation 

 of vegetable mulch, and for the use of large quantities of pen manure. 

 These measures have not been so necessary in Trinidad, with a climate 

 more favourable to vegetative vigour, consequently, (since in no 

 industry, least of all that of agriculture, are methods much better 

 than circumstances enforce), they have not been practised. Favour- 

 rability of climate, however, can be offset by deficiencies in soil 



conditions, just as its defect can to a considerable extent be compensated 

 for by improvements in the same. The deterioration which has become 

 evident in Trinidad, be its causes what they may, and which finds its 

 expression in the increased prevalence of blight, has now rendered 

 necessity the resort in some degree to similar measures. 



THE ROLE OF THE FROGHOPPER. 



29. So far the discussion has proceeded with only casual references to 

 the insect whose prevalence is regarded by many as the beginning and 

 end of the matter. Into the entomological aspect of the case it is not 

 my part to enter, nor as I have explained, was I a witness of the active 

 operations of the pest. The remarks ^v•hich follow have reference to 

 the opinions which I formed as to its probable share in the production of 

 the conditions of blight as it was visible in December and January. 



30. Approaching the subject of froghopper injury with an open 

 mind, I became persuaded from consideration of the evidence that an 

 infestation of froghoppers is capable, in some instances, of quickly 

 producing severe effects, marked by the drying-up of the leaves, on even 

 healthy and vigorous canes growing in rich and well-tilled soil. The 

 history of two cases brought to my notice in districts widely separated 

 had considerable weight in bringing me to this conclusion. Both 

 fields had been attacked and severely damaged as plant canes. The one 

 field had since given, without further attention, two good crops of 

 ratoons and was still, as I saw it, in satisfactory condition. The other 

 field was attacked in 1917, after thro? vears of fallow anl the use of pen 



