14 TRINIDAD AND TOBAGO BULLETIN. [XIX. 1. 



15. Describing the process in another way: the youngest shoots, 

 ■which have no developed steui, fail when theii- current leaves are 

 destroyed ; each older shoot is able to go on forming new leaves, as the 

 older ones are destroyed, to an extent proportional to the development of 

 its stem. In a continued infestation each shoot in turn fails to maintain 

 an adequate amount of leaf surface, and in canes below a certain 

 standard of ripeness the terminal bud succumbs and the stem begins to 

 die back from the top. 



INFLUENCE OF ROOT FUNGI ON BLIGHTED 0.\NES. 



16. The development of the general condition above described is 

 commonly closely accompanied by a notable increase of the develop- 

 ment of root fungus, especially of the Odontia type. The increase in 

 the quantity of dead material available for its support may be regarded 

 as largely resj^onsible for the conspicuous extent to which tlie 

 fungus frequently occurs. The manner of its appearance and its 

 relation to the blighted stools strongly suggest that its increase in these 

 •circumstances is consequent upon the existence of froghopper blight. 



17. The extent to which froghopper injury is increased by the 

 ■presence in quantity of root fungus is difficult to estimate, and is no 

 doubt highly variable according to circumstances. Knowledge of the 

 ability of root fungus to attaclc weakened canes would lead one to 

 expect a very considerable effect, and this the observations made 

 •during both my visits have strongly confirmed. It is true that cases 

 have been seen this year where under the stimulus of favourable 

 weather badly blighted canes have resumed vigorous growth in spite of 

 root fungus, but in other cases, and especially after the wider attacks of 

 last year, areas were seen in which the blight initiated by froghopper 

 had assumed a permanence which could only be attributed to the pre- 

 vailing infestation of the fields with root disease. 



18. In accordance witli the often-stated nature of root disease its 

 effectiveness in this direction is governed, not only by the condition of 

 the cane as affected by the insect, but by the condition of the field as to 

 tilth and fertility and by the nature of the prevailing weather. 



CONTRIBUTOHY EFFECTS OF MOTH-BOEERS. 



19. The present season is marked hy a very notable increase over 

 last 3'ear of damage by the small moth-borer Diatroea. Rather heavy 

 infestations were seen combined with froghopper damage. It was 

 evident that in such cases the effects of froghopi^er would be seriously 

 exaggerated if the borer damage were left out of account. The same 

 consideration was seen to apply, in other instances, to damage occasioned 

 by the large moth-borer, Castnia. 



COMPARISON OF FROGHOPPER BLIGHT WITH OTHER 



DISEASES. 



20. Sereh Disease. The writer was very much struck in some 

 instances by the close correspondence between the effects of froghopper 

 and the descriptions and photographs pubHshed of the Sereh disease of 

 Java. It may be recalled that Dr. Gough noticed this in certain, 

 particular cases and submitted specimens to Professor Went of Java, 



