1921.\ SUGAR CANE FESTS AND DISEASES. 113 



December 5. This gives the intervals as 56 days for the first brood, 

 58 days for tlie second brood, and 58 days for the third brood. (In my 

 report the figures given are 57 days for tlie first brood and about 

 58 days for each of the other two). 



Relation betwken Damage and Soil. 



Observations made this year serve to emphasise strongly the relation 

 between froghopper infestation and soil noted in my previous report 

 (p. 1091. 



The infestation was, with a few exceptions, not sufliciently serious 

 to take the best fields, so that the effects of soil difterences were 

 unusually well marked. A number of fields have been found where 

 the soil changes correspond exactly to variation in infestation. 



[a.) Field 24 E. Union Hall Estate has two ndges of heavy poor 

 red soil in what is otherwise a fairly good field. Froghoppers attacked 

 this field in the second brood and the damage was very njuch more 

 severe on the ridges than in the hollows between them. 



(h.) In 1917 Field 33, Tarouba, was damaged on the slope of the hill, 

 but was much better at the foot. Analysis showed the soil to be less 

 acid and much richer in lime at the foot than the slope. This year the 

 field alongside, which has a similar slope and fiat parts was damaged in 

 a manner exactly corresponding to that of Field 33 in 1917. There is 

 no doubt that the same soil influences are at work. 



(c.) Field No. 2 N. Union Hall, had in 1918 and 1919 a belt of 

 damaged canes running diagonally across the field and up ihe slope. 

 The canes on either side of this were in both years much less damaged. 

 This year the field has been ploughed up and the exposed land shows a 

 belt of red clay soil across a darker and more loamy soil, the red belt 

 corresponding exactly to the previously observed limits of the damage. 



(d.) On Cupar Grange Estate there were one or two spots of severe 

 injury in an area of black soil, these spots being planted with L'ba cane. 



Inquiry showed that the soil in these l^laces, although black, was so 

 heavy and stiff that other varic ties had failed to grow, and Uba had 

 been planted as a last resort. Although Uba is known to be consider- 

 ably resistant to froghopper attack the inliuence of the soil was so great 

 that the damage was confired to the bad patches although surrounded 

 by more attractive varieties of cane. 



(e) Field 102 Cedar Hill, consists of along slope and a small li at area 

 at the fcot. The second brood of froghoppers in 1920 did considerable 

 injury to the canes on the slope while tliose at the foot remained 

 untouched and quite green. An examination of the soil in a ploughed 

 field alongside which included the same slope and flat areas showed 

 that the soil on the slope was a heavy red clay while that in the flat was 

 much darker in colour and of a lighter texture. 



(/.) The froghopper damage this year at Cedar Hill Estate was as 

 great as in any previous year, but the fields damaged were without 

 exception on the two belts of red soil as shown in the map of this 

 estate in my previous report, p. 110. 



{(/.) In the Northern sugar district one field in an area of com- 

 paratively light soil was severely injured. I was informed by the 



