CANE SUGAR. 



for the distribution of the spores of the Ithyphallus coralloides. The dissemina- 

 tion of typhoid, cholera, and dysentery by means of flies is now well recognized ; 

 in these cases the flies visit human excreta, and carry the causal organisms to 

 unscreened food and drink. 



5. Destruction of dead cane, and of trash, as such material forms a habitat 

 for certain organisms parasitic on living cane. 



6. Rotation of crops. The peculiar proneness of the cane to disease lies 

 perhaps in the wide-spread practice of growing it continuously on the same 

 areas; similar observations with regard to wheat grown continuously at 

 Rothamsted have been quoted in Chapter VI. It is, perhaps, the various 

 forms of ' root disease ' which are most helped by this system. If other crops 

 not susceptible to the fungi attacking cane were grown in rotation, the fungus 

 would be starved, and would tend to disappear ; as it is, the fungi have often a 

 continuous habitat, and the soil becomes infested. Similarly lack of hygiene 

 may lead to houses and districts becoming infected with pathogenic organisms. 



7. Selection of immune varieties. The work of Experiment Stations has 

 been largely directed to this end ; and already seed varieties are grown on the 

 large scale where, owing to the prevalence of disease, older varieties such as 

 the Bourbon and White Transparent quite failed. An interesting point in con- 

 nection with immunity is Erwin Smith's failure to infect the cane D 74. with 

 the Pseudomonas vasculaium (Cobb) to which 'gumming' is due. The Yellow 

 Caledonia, or "White Tanna, in Hawaii is also to be noted as a disease -resistant 

 variety. In Java, the Sereh disease was, and is, controlled almost entirely by 

 the selection of immune varieties. 



In certain cases immunity may be connected with hardness of rind. 



8. Avoid all processes, such as high trashing, that tend to injure or to 

 expose the softer parts of the cane. 



9. Inspect and disinfect all canes received from foreign countries. This 

 process of quarantine can also be extended to a self-contained cane-growing 

 district in some areas of which disease is known to be more prevalent than mothers. 



The Ccnnection between Pests and Diseases. When 'rind 

 fungus ' was prominent in the "West Indies in the nineties, great attention was 

 paid to the possible sequence of disease on insect damage. This view has now 

 become generally accepted ; to many diseases the hard outer rind of the cane 

 acts as a partial barrier. 



Disease Epidemics. The history of the cane abounds with 

 instances of sudden and destructive disease epidemics. In Reunion, during 

 the years 1845-1851 a yellow cane qui n'etait autre que la veritable 

 Otaheite was so attacked that it was necessary to entirely replace it with 

 other canes ; this epidemic spread to or appeared simultaneously in Mauritius, 

 and is the one to which Darwin refers in his Variation of Animals and Plants 

 under Domestication, mentioning the substitution of a red cane (probably the 

 Belouguet or Black Cheribon) for a white cane (probably Otaheite). This 



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