118 FROGHOPPER BLIOIIT OF SUGAR-CAXE. 



attack to result from insects passing on in the same field, and the 

 reduction of waste Jand will reduce the number of centres of indirect 

 infection. 



Further discussion and some suggested types of rotation will be 

 found on p. 134 in the Section dealing with the Control of the Blight. 



TILLAGE. 



It follows from the relation already discussed between the condition 

 of the soil and the prevalence of blight that any process that will bring 

 the soil to a more open, lighter, and looser state will have an effect in 

 removing the blight. 



In the past most of the preparation of the land and tillage has been 

 done by hand labour with forks. These are being now gradually 

 replaced by ploughs and cultivators drawn by cattle and mules, and 

 there is little doubt that the near future will see a considerable increase 

 in the use of tractors. 



The beneficial effect of cultivation has been seen in many cases. 

 Thus two fields of young plants side bv side on Tarouba Estate in 1918 

 were both the same age, but differed onl}' in that the IManager had been 

 able to give one of them a more complete cultivation than the other.. 

 In the less cultivated field, not only was the soil in a visibly poorer tiltli 

 and the young canes much weaker, but froghoppers were at least ten 

 times more abundant. 



A still more striking case was at Harmony- Hall where in September 

 1918 half of the field badly damaged by froghoppers was forked 

 throughout between the rows and down the edges of the drains No 

 particular effect was noted that year, but the following July the first 

 brood of froghoppers was at least twice as abundant on the unforked 

 part of the field as on the forked part, and the leaf damage was 

 much more obvious. There was in fact a distinct line across the field 

 separating the badly damaged area from the slightly damaged area, and 

 this line corresponded to the division of the forked area from the unforked. 



A curious and unexpected fact, which is as yet unexplained, is that 

 the canes on the unforked half although more damaged were, until the 

 advent of the blight, distinctly larger than those on the forked half. 



It will of course be realised in view of the manj' other factors 

 influencing the abundance of the froghopper, that sometimes a field will 

 be blighted in spite of the best tillage, but this is no proof that the 

 cultivation has been injurious. 



In a few cases however, the sudden apppearance of blight has been 

 put down by Managers as being directly due to iniplemental tillage, and 

 in particular following on the use of the sub-soil plough. It is possible 

 that in some boils with a sour undisturbed sub-soil the use of deep 

 implements might have a temporary injurious effect, but in most cases 

 it is probable that the canes would have been blighted in any case, 

 particularly when it is recollected that the leaf injury to the cane 

 continues to increase for about thi'ee weeks or more after the height of 

 the brood of froghoppers and the ploughs are often sent through when 

 the field begins to look poor. 



It is not the purpose of the present report to discuss the relati\o 

 advantage of animals versus tractors in agriculture, but it might be 

 mentioned that, from the point of view of froghopper control, more pen 



