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No WELL (W.). Investigation of Froghopper Pest and Diseases of Sugar 

 Cane. — Trinidad & Tobago Council Paper no. 39 of 1919, Port 

 of Spain, 20th February 1919, 10 pp. [Received 5th June 1919.] 



In consequence of the discovery made by the entomologist in charge 

 of froghopper investigations in Trinidad, that the prevalence in sugar- 

 cane fields of the condition known in general terms as blight in many 

 cases did not correspond with the severity of froghopper infestation, 

 the conclusion was reached that an additional factor must be involved. 

 As it was suspected that this factor was a root disease of fungoid 

 origin, the co-operation of a mycologist with experience of the effects 

 of root disease in places where no complications with froghoppers 

 exist was desired, and the present report embodies the results of the 

 mycologist's observations during the period from December 1918 to 

 February 1919. When the investigation began, infestation by the 

 froghopper [Tomaspis saccharina'] was practically over for the duration 

 of the current crop, while the period covered, namely, the last weeks 

 of the wet season and the beginning of the dry, was the most suitable 

 for estimating the position held by root disease in the final condition 

 of blighted fields. It was evident from the first that to the froghopper 

 were ascribed practically all the causes that may operate to produce an 

 unhealthy appearance in standing canes. In many fields other adverse 

 conditions were present to a degree that would probably be sufficient 

 to account for the poor state or failure of the yield, but concentration 

 upon the purely entomological aspect of the subject has not only 

 failed to bring the hoped-for relief, but has delayed progress in more 

 promising directions. 



Both the onset and persistence of root disease depend on a condition 

 of weakness or debility in the cane, which may be caused by a variety 

 of adverse conditions. The general nature of the disease is discussed, 

 the factors influencing its occurrence and the means that may be 

 adopted for its reduction. Examination of the work of froghoppers 

 in infested cane showed that the insects are capable in some instances 

 of quickly producing severe effects, marked by the drying up of leaves. 

 In the majority of cases, however, where other conditions are good, 

 recovery seems to begin as soon as the infestation is over, and, except 

 for delayed growth, definite recovery generally ensues. It is therefore 

 concluded that froghopper infestation is not capable alone of producing 

 the permanently disabled condition that exists on many sugar-cane 

 areas and this obviously constitutes the really serious feature of the 

 situation. The severity of froghopper injury on fields affected by 

 adverse conditions is explained by the plants lacking full vigour, 

 having an ill-developed root-system, and thus being less able to with- 

 stand the drain vipon their sap which the feeding of the insects involves. 

 This might account for the drying up of leaves, but does not by itself 

 account, in the case of a plant with the powers of recovery charac- 

 teristic of sugar-cane, for the continuation of the condition after the 

 infestation has subsided. Nor can anything less than a heavy infesta- 

 tion produce even this effect, and it remains to be shown how the 

 attacks of the small numbers of froghoppers sometimes held respon- 

 sible can affect so hardy a plant, apart from a toxic influence of which 

 no evidence has been produced. Under the present methods of 

 Trinidad agriculture, a certain amount of root fimgus is sure to exist 



