19fil.\ SUGAR CANE PESTS AND DISEASES. 121 



Every fo2) cutting from Llie diseased stalks came up diseased. Of 

 the bottom cuttings there were twenty-throe diseased, one healthy and 

 three showing both diseased and healthy shoots. In two of these latter 

 the diseased shoots were growing from the upper end of the cutting and the 

 healthy shoots from lower down. In the third there were two diseased 

 shoots growing from one side of the cutting and one apparently healthy 

 shoot from the opposite side. This last shoot after having produced 

 about half a dozen quite healthy leaves was showing doubtful traces of 

 disease on the innermost leaves in the middle of February 1921. 



These are apparently canes in which the " virus " of the diseass 

 had, owing to recent infectioji, not reached down the cane to the point 

 at which the cuttings were taken. 



It follows from the above that if recently infected stalks were cut 

 off close to the ground it miglit be possible in some cases to prevent the 

 infection from spreading to that part of the stool below the ground, 

 wliich should then send up healthy shoots. 



This was in distinct opposition to a suggestion made by Mr. C. M. 

 Koach, who fouiid that one of the worst infected fields belonging to a 

 small farmer had been accidently burnt when commencing to grow and 

 had been cut back to the ground. He believed that the new growth 

 miglib be more heavil}' infested than the old. 



To test between the two alternatives seven stools, which were 

 receiitly infected with mosaic and contained diseased and healthy 

 stalks, were cut down to the ground level on November 2. On 

 December 18 {i.e. seven weeks later) the new growth was examined 

 and in four stools was found to be entirely free from mosaic, while in the 

 other three there were sixteen healthy shoots and seven diseased. On 

 February 10, 1921 the four healthy stools were still without signs of 

 disease. The results of this experiment were so unexpected that on 

 December 23, 1920 50 stools with one or more shoots recently infected 

 were cut down to ground level as before and allowed to grow. On 

 February 10, 1921 (seven weeks later) the new growth was examined. 

 Owing to carelessness on the part of some weeders only 34 stools grew, 

 but of these 11 were quite healthy, the others including 16 definitely 

 diseased and 7 doubtful. 



These ex2)eriments are being continued with the addition of removing 

 from each stool all diseased shoots as soon as they are noticjd in order 

 to see if by this means the stools to which the infection has reached 

 below ground level can be eventually freed from the disease. 



The value of these experiments lies in the fact that they indicate 

 that it may be possible to keep mosaic disease under control towards ihe 

 end of the year, without the wasteful and costly removal of whole stools 

 from the ground, by more frequent removal of the diseased shoots. 



Experiments are now being planned to test the possibility of poisoning 

 the diseased shoots when cut to pi'event new growth from these portions 

 of the stool. 



February, 1921. 



