1920.] 



MOSAIC DISEASE OF SUGAR CANE. 



35 



The percentage of infectioa varies from 8-4 per ceni. in plant canes 

 of B. 156 to 77'7 percent, in tliirJ ratoons of D. 115. 



The loss in diseased canes as compared with healthy varies from 

 S8'6 per cent, in first ratoons of B. 16536 to 0*48 per cent, in first 

 ratoons of B. 10650, while H. 146 even shows slight increase. In 

 Table III the varieties in Table II are arranged in order of the damage 

 suffered. 



TABLE III. 



Percentage loss. 



38-6 

 35-1 

 31 -a 

 2G-4 

 22 5 

 21-4 

 19 

 16-9 

 12-5 

 10-G 



9-4 



8-9 



7-9 



5-3 



4-9 



2-2 

 ■0-48 

 Very slight increase 



Variety. 



1st} Ttatoons. 

 Plants. 

 .I'lants. 

 3r(l Ratoons, 

 1st Eatoons. 

 I'lants. 

 Plants. 

 1st Katoons. 

 3r(l Ratoons. 

 Plants, 

 riauts. 

 3r(l Ratoons. 

 3rd Ratoons. 

 3rd Ratoons. 

 Plants. 

 Plants. 

 1st Ritoons. 

 1st Ratoons. 



The actual lo^s on the p'ots t9Hteil varied from 0"25 per cent, in 

 B. 10650 to •27-83 per cent, in B. 1.536. 



The cankering of the stem was very distinct in B. 16336 and 

 B. 64i:0. 



Experiments are now being carried o i at St. Augustine to st'idy the 

 spread of the disease and to find at whi jh ti ne of the year it is most 

 rapid. Cuttin-^s frjm diseised and hea thy canes are also beaig planted 

 side by side to test the conchision reached in Porto Rico that every 

 cutting froiu a diseased plant is diseased. 



ERADICATION AND CONTROL. 



The only way known at present in which tlie Mosiic dif eaie can be 

 prevented from becoming a serious danger to thj Trinidad sagar ind istry 

 is by continual inspectioa and the continual destruction of all diseased 

 stools. 



It is found in Porto Rico that this is a practicable method of cmtrol 

 whenever the infection does not exceed 25 per cent. When the infection 

 is higher tha a t lis, the field should be replanted after the crop ha3 be^x 

 cut, with cuttinjs care!ully selected from healthy stools. 



