28 FROGllOrPEU DLiGIlT OF SUGAR-CANE. 



definite streaks on the leaves in the case of root disease. There is only a 

 severe wilting which may result finally in the death of the leaf. The 

 visi!)le presence of the fungus is not a proof that it is concerned in the 

 injury as it may exist in quantities on the stool as a saprophyte, that is 

 to say living on alread}' dead tissue, and on the other hand it may be 

 doing serious damage to the roots without any considerable surface 

 development of mycelium. 



In the canes damaged by root disease only, there is a very considerable 

 shortening in the lengths of the internodes, similar to that caused by 

 drought, but there is not the same narrowing of the joints that is con- 

 spicuous in the present blight. 



Damage from root fungus does not usually spread over such large 

 areas as froghopper blight and often appears on a few stools in a field. 

 The froghopper maj' be abundant in small areas, but the smallest I 

 have seen included at least twenty or tliirtj' stools. 



Another important difference is that root disease, while capable of 

 rapid increase and decrease in a field,- usually in correlation with 

 weather conditions, has nothing of the definite periodic recurrence of the 

 froghopper blight as found in Trinidad. 



Sereli Disease. This disease is a serious trouble in the sugar grow- 

 ing districts of the East. In 1911 Dr. Gough suspected its presence in 

 Trinidad and sent specimens to Dr. Went in Java. The latter found in 

 the diseased canes nearly all the known symptoms of a mild attack of 

 Sereh with the exception of the staining of the vascular bundles (which 

 was however seen by Dr. Gough) and says " If all these canes had come 

 from Java I would not have hesitated for a moment and would have 

 declared them to be attacked by Sereh." As Sereh had never been 

 recorded outside the East Indies he merely suggests that " Trinidad is 

 suspect in regard to Sereh and it will be well for planters to keep a 

 keen look out for any more serious signs of the disease." [West Indian 

 Bulletin XII p. 558.) 



On the other hand a Committee of the Board of Agriculture, who 

 examined the suspected fields about a year later and found them no 

 worse and probably better than the year before, was " not prepared to 

 agree with Dr. Went's conclusions." 



There is no doubt that the symptoms induced in the cane by frog- 

 hopper attacks in Trinidad have a very close resemblance to those 

 described for Sereh in the East. The shortening of the internodeS, 

 resulting in a fan-like arrangement of the leaves, the starving and final 

 destruction of the growing point and the consequent death of the 

 smaller shoots, the reduction in the size of the leaves, the appearance of 

 red streaks at the internodes, the developiuent of gum pockets in the 

 young internodes, and the shooting of the eyes and the development of 

 adventitious roots, all are common to both diseases. In fact the 

 illustrations on Plates IV and V showing canes suffering from froghopper 

 attack in Trinidad might well pass for illustrations of Sereh in Java. 



At the same time the final symptom of Sereh, the persistence and 

 continual increase of damage in infested stools from year to year, the 

 character that makes it so much to be feared, is not found in Trinidad, 

 nor on the other hand are the streaks on the leaves, so characteristic of 

 froghopper attack found in cases of Sereh in the East. 



Mr. Nowell and myself have come to the conclusion that the disease 

 does not exist here, but that a series of similar symptoms are produced 

 in the canes by a similar physiological disturbance, which however 

 arises from a quite different cause. 



