8 TBINIDAD AND TOBAGO BULLETIN. [XIX. 1. 



SUGAR CANE BLIGHT IN TRINIDAD: 



A Summary of Conclusions-* 



By W. Nowell, D.I.C, and C. B. Williams, M.A., F.E.S. 



I. THE FROGHOPPER. 



1. An infestation of froghoppers can produce a definite form of 

 bliglit without necessary co-operation of other insect or fungus 

 agencies. 



2. The characters of the condition so produced consist of :— 



(a.) Leif injury, beginning with tlie formation of elongated spots 

 and patches, pale at first, then red brown, and finally dry and 

 silvery brown ; wliich injury in well-developed infestations 

 results in the premature withering of most or all of the leaves. 



(&.) The more or less complete arrest of growLh, in which the 

 well-developed canes in a sto il suffer little, the youngest 

 shoots die outright, and the slioots of intermediate age are 

 affected in inverse proportion to their size. (It follows from 

 this that the better the caues are developed the greater is their 

 resisting power). 



3. This condition differs, in plainly recognisable characters, from 

 that produced by any form of root disease known to the writers. 



4. (a,.) In some cases the appearances produced agree very closely 



with those described for the Sereh disease of Java, but the subsequent 

 history of the stools shows that the resemblance is one of appearance 

 only, the continued degeneration in successive years characteristic of 

 Sereh being entirely absent. 



\fi.) Nothing has been seen to suggest that the Motthng or Mosaic 

 disease, now giving trouble in Porto Eico and Louisiana, is involved in 

 the production of blight. 



5. The general condition described seems to be mainly the result of 

 injury to the leaves, as appears both from the observation of attacks 

 and from consideration of the symptoms of the affected stools. This 

 conclusion is supported by the following evidence :— 



{a.) The condition reaches its most acute phase shortly after the 



chief flights of adult froghoppers. 

 (6.) ^Yhere there is no complication with root disease or hindrance 

 by drought, the stools, even in the case of low ratoons in 

 which all or nearly all the shoots are killed to the ground, 

 resume vigorous growth when the brood of froghoppers has 

 passed. 

 (c.) The root system and underground stem system in these 

 uncomplicated cases do not appear on examination to be 

 seriously affected. 

 6. In the present year (1919), which is one in which the froghopper 

 is near its minimum, the third brood infestations can be classified as 

 follows : — 



(a.) A belt of infestation in the Kaparimas which coincides closely 

 with the occurrence, in bands and patches, of a particular type 

 of red clay soil. 



* Prej ared as a prelirniiary report on investigations in 191!). 



