54 TRINIDAD AND TOBAGO BULLETIN. [XVIIL 2. 



It was not until the wet season of 1918 that I was able to get any 

 accurate information on this question, but the results when obtained 

 confirmed the suspicions of the previous year. Two methods were 

 used to get an estimate of the number of Froghoppers present. The 

 first consisted of counting the number of Froghoppers visible on a given 

 number of stools in a field and then calculating the probable total per acre. 

 The second method, which is purely comparative, consisted of finding 

 the number of adults caught in similar light traps placed in different 

 fields. 



Both methods are subject to many errors, but the results were too 

 striking to be explained in this way. Fields were badly damaged when 

 only about ten adult froghoppers per stool could be seen at the height 

 of the brood; other fields in which thirty or forty adults per stool 

 -could be seen were only slightly injured. One field in which 20,000 adult 

 Froghoppers were captured in one night in four light traps suffered 

 but slightly, while a field in which the numbers never rose above 3,000 

 was almost completely destroyed. 



Results of this kind were a very strong indication that some other 

 factors were involved besides the mere numbers of the Froghopper. 

 Many of these were known — the age of the cane — the soil — the rainfall — 

 manurial treatment — drainage, &c., but although the effect of all these 

 could be seen they were of themselves insufficient to account for the 

 differences found. 



Attention was then turned to the possible association of the 

 Froghopper with other insects or with fungi or even the possibility that 

 it introduced some toxic substance into the cane plant. No insect 

 could be found whose presence would explain the conditions, but when a 

 search was made for fungi it was immediately seen that certain species 

 of root fungi were in almost more constant association with the condition 

 known as " blight," than the Froghopper itself. 



In September 1918 Mr. J. V>. Ilorer visited witli me certain fields 

 which had led me to these opinions and agreed that in nianj' of these 

 root fungi were responsible for the greater part of the blight. 



In October 1918, as Mr. Ilorer was leaving the country, 1 requested 

 the Froghopper Connnittee to invite the co-operation of Mr. Nowell, 

 Mycologist to the Impei'ial Department of Agriculture. As a result he 

 visited Trinidad from December, 1918 to February, 1919 and the follow- 

 ing report gives the results of his observations. They are I think of 

 particular value, as he has had considerable experience of the damage 

 due to root fungi in islands where the Froghopper does not occur. 



In view of the results of these various investigations I think it can 

 be safely said that root fungi are responsible, directly or indii-ectly, for 

 a considerable portion of the damage generally attributed to Froghoppers. 



RELATION BETWEEN FROGHOPPER AND ROOT FUNGI. 



There remains the question as to the relation between the Froghopper 

 and the root fungi. Is each independent of the other '? Does the 

 presence of one predispose the cane to the attacks of the other ? Or 

 are both dependent on some similar environmental conditions. 



