134 FROOHOPPER BLIGHT OF SUGAR-CANE. 



much sub-soil at any one time. Implemental tillage should not be used 

 when the soil is too wet, as in this condition more harm than good can 

 be done. 



In this connection attention might be drawn to the unfortunate 

 conditions existing in a few localities in Trinidad, where the boundaries 

 of the fields bear no relation to the changes of soil. As a result one 

 field may contain two entirely different soils which require entirely 

 different treatment and cultivation. Sometimes the soil changes are so 

 irregular that this cannot be avoided, but wherever possible in relay- 

 ing out fields their boundaries should be made to correspond as closely 

 as possible to the visible soil changes, so that tillage may have more 

 uniform effect. 



Selection of Varieties. 



The question of relative resistance of varieties has already been 

 fully discussed in a separate report (Williams 193 9 D.) and summarised 

 on p. 119 of the present report. There are no immune varieties, but 

 ,some are apparenth' a little more resistant than others. The best of 

 these are "Uba" and " Badilla," but neither is generally acceptable to 

 the planter. Both require very heavy pressure in the mill, and '' Uba" 

 is difficult to cut in the field, while "Badilla" is very slow in its growth. 



Recently some seedlings from " Badilla" have been obtained which 

 show great promise, but at present it is not possible to say if they retain 

 the resistant properties of the parent cane. 



Among the other varieties there is so little difference in resistance and 

 so much depends on soil and other estate conditions, that the planter 

 will px'obably be best guided in his choice of varieties by other circum- 

 stances than the prevention of disease. 



Reduction of Ratooning. 



The relative liability of plant and ratoon canes to attack is discussed 

 on p. 115. It follows that the less the relative proportion of ratoon 

 canes to plant canes on an estate, the greater the freedom from attack. 



This policy is being gradually adopted on one or two estates. On 

 the fields which have shown themselves particularly liable to attack 

 only plant canes and first ratoons are allowed to grow. 



It is more expensive to grow canes in this way instead of allowing 

 them to produce second or third ratoons, but against this has to be put 

 the greater freedom from froghopper blight and root disease, rapid 

 improvement of the soil by more frequent cultivation (especially if some 

 rotation crop is introduced, see below), and the higher average yield per 

 acre, which reduces the overhead charges. 



The method is to be strongly recommended from an entomological 

 point of view, particularly' in the low-lying districts where improvement 

 of soil and drainage is a difficult matter. It is for the planter to decide 

 which fields require such treatment and which are sufficiently good to 

 stand continued ratooning without deterioration. 



Rotation. 



In every country in the world agriculturists are driven sooner or later 

 to a rotation crop. In temperate climates, 'where conditions are severe 

 and agriculture old-established these rotations have developed to an 

 axiom of agriculture and good systems are already worked out. In 

 tropical countries where growth is easier and, as a general rule, agricul- 

 ture is a more recently crganised industry, rotation is still a matter of 

 trial and experiment and even in some cases only of anticipation. 



