64 TBINIDAD AND TOBAGO BULLETIN. [Xrill. 2, 



manure and sulphate of ammonia. The soil is black and deep and part 

 of the field is a rich and well-drained bottom. The ratoon crop on it 

 was this year exceedingly vigorous. 



31. The instances specified illustrate the capabilities of the insect for 

 harm with a clearness which is lacking from the ordinary run of cases,, 

 which occur on ratoon crops in which the condition of the canes is 

 usually complicated by root disease and often by cultural disabilities. 



32. It is important to note that in these cases, where other conditions 

 were good, recovery seems to have begun as soon as the infestation was 

 over, and no persistent after-efTects were experienced. 



33. It is, I think, admitted that the effects of the pest are not 

 commonly apparent on plant canes or on canes growing under conditions 

 entirely favourable, and I was led to infer, from the above cases on plants 

 and from the healthy, though delayed, condition of several fields of 

 ratoons which had been infested, that under these circumstances definite 

 recovery, save in the matter of time, is likely to ensue. From this, one 

 must conclude that froghopper infestation is not capable, without the 

 co-operation of other adverse circumstances of producing the permanently 

 disabled condition which existed on many areas at the time of my visit, 

 and which obviously constitutes the really serious feature of the 

 situation. 



34. The facts as to the distribution of blight afford strong support to 

 this conclusion. There are favoured estates on which no injury of the 

 kind has ever been experienced. There are many others with land 

 of unequal quality or unequally treated, in which the trouble, when it 

 has appeared, has always been confined to the poorer fields. The estates 

 on which the trouble is most widespread and frequently recurrent are, 

 in several cases if not in all, subject to disabilities, arising from their 

 situation or from their history, which are perfectly well known to 

 those concerned. 



35. There are instances which cannot be included with these, where 

 the trouble has arisen unexpectedly on land as good and as well treated 

 as is commonly found necessary to ensure satisfactory crops. Some 

 of these, I am persuaded, could be accounted for by an intimate study 

 of the conditions prevailing at the time ; there are a few, it must be 

 frankly said, in which even the possibility of an explanation on these 

 lines was not evident, at least to a visitor. In a general survey such 

 instances are very far from prominent. 



36. The simplest explanation of the severity of froghopper injury 

 on fields affected by advei'se conditions, is that plants lacking full 

 vigour, with an ill-developed root system, are much less able to withstand 

 the drain upon their sap which the feeding of the insects involves. 

 This might account for the general drying-up of leaves which is the 

 first effect of an infestation : I do not see how it can by itself account, 

 in the case of a plant with the powers of recovery characteristic of 

 sugar-cane, for the continuation of the condition after the infestation has 

 subsided. Nor can anything short of a mass infestation be admitted 

 to be capable of even this effect. The exponents of the froghopper have 

 yet to show how the sucking of the comparatively small numbers of 

 insects sometimes held responsible can affect so hardy a plant apart 

 from a toxic influence of which no evidence has been produced. 



