134 [PT. ii 



CHAPTER XV. 



THE DISEASES OF PLANTS IN THE TROPICS, AND 

 THEIR TREATMENT. 



INSECT and fungus enemies to plants are very numerous in 

 the tropics, and seem, probably owing to the fact that so many 

 crops are perennial, and to the fact that there is no winter to 

 check them, on the whole more injurious, and more to be 

 feared, than in Europe. The great classical example of injury 

 is of course the terrible attack of the Hemileia vastatrix, or 

 coffee-leaf fungus, upon coffee cultivation in Ceylon from about 

 1875 to 1885, during which period a once very large and pros- 

 perous industry was reduced to abject ruin. 



Nowadays, there seems much less likelihood of such an 

 event occurring again, since the rapidly extending agricultural 

 departments in the various tropical countries are in most cases 

 provided with the help of a Mycologist for the study of fungus, 

 and of an Entomologist for that of insect pests, and, still more 

 important than this, the agriculturists themselves are now 

 realising that it is much more to their advantage to give timely 

 notice of any attack of disease upon their cultivations and to 

 get suggestions early as to the best mode of treatment, than to 

 conceal it until perhaps it has got such a hold that it is no longer 

 possible to eradicate it. True it is that in this way many 

 diseases are treated which would not absolutely require such 

 treatment, i.e. diseases which are merely sporadic and would 

 not spread, but this does not affect the general position that all 

 diseases are in general treated early, and that disease is thus 

 usually kept under control. It must also be admitted that it is 



