•SECTION VIII. — FACTORS INFLUENCING BLIGHT PREVALENCE. 117 



ROTATION. 



In the greater part of the sugar area of Trinidad either no rotation 

 at all is in practice, the fields being replanted with canes as soon as the 

 old ratoons are worn out, or a very primitive and inefficient rotation 

 is made by abandoning the land, for a longer or shorter series of years 

 between successive cane plantings, to whatever plants and bush are able 

 to take possession. 



The break may be an^'thing from one to as many as ten years in 

 length according to the amount of land available, and the character of 

 the vegetation varies slightly according to the length of time that it 

 remains untouched. There is usually a thick growth of grasses, mixed 

 in the first year or two witli shoots from the old cane stools, and a 

 higher bush growth of Black Sage {Cordia cylindrostachya) , Christmas 

 Bush (Enjyatorium odoratum), guava, etc. 



Neither of these systems has anything to recommend it from jibe 

 point of view of the control of blight. When the field is replanted 

 immediately^ it is almost invariably done by putting the fresh cuttings in 

 between the old plants which remain there with their froghoppers, 

 moth-borers and root-fungi as a source of infection within a few inches 

 of every young stool. Later they may be dug up and turned over but 

 this, as often as not, only serves to bring the root-fungus infection still 

 ■closer to the young plant. 



If the land is abandoned for a series of years conditions are not 

 much better. The old stools are not dug out and on them root-fungi 

 persist for more than a year, while the grasses which grow up between 

 them serve as an excellent breeding ground for the froghopper and a 

 source of infection not only to that field when it is replanted but also 

 to neighbouring fields which may have been more carefully cultivated. 



In addition the undisturbed and undrained condition of the soil has 

 an accumulative injurious effect on the soil which we have found to be 

 so important in connection with the survival of the froghopper. 



Many examples could be given of severe blight in fields which had 

 been abandoned for years. Thus at Union Hall Estate in 1919 a field 

 was severely damaged that had been abandoned as part of a burial 

 ground for twenty years previousl3'. At Hermitage in 1917 a field was 

 damaged that had been ten years abandoned, and two fields damaged at 

 Caroni in 1906 are mentioned as having been out of cultivation for ten 

 years. It will also be remembered that one of the fields damaged at 

 Grenada (p. 44) had been out of cultivation for eight years. 



Other cases are known of the spread of blight from abandoned fields 

 into healthy ones. Thus in one of the earliest attacks of blight on 

 Cedar Hill Estate in 1900 the Manager noted that all the damaged 

 fields were alongside an area of abandoned land, and at Petit Morne 

 in 1919 a field of plant caiies was attacked along one edge borJering on 

 an abandoned farmer's plot, under conditions that left no doubt that the 

 blight had spread from this spot. 



Under estate cultivation, a manager has only himself to blame 

 when conditions like these arise, but, under the present adopted policy 

 of encouraging a multiplicity of small owners, cases of spread of disease 

 from one land to another will cause much more dispute and trouble. 



With a proper break in the cultivation, with all fields not under cane 

 completely cleared and planted in some other crops for at least six 

 months and preferably for eighteen months, it is impossible for an 



