Consequently the occurrence of epidemics under the conditions described is by no means unknown. One of the most famous examples of modern times is afforded by the coffee leaf fungus Hemileia vastatrix, which, in combination with other diseases, entirely ruined the coffee planting industry of Ceylon in the seventies and early eighties. This calamity has taught planters in general a lesson which it is to be hoped they will not readily forget; for if a disease be taken in hand in its early stages, when only a few individuals are affected, it is generally possible to cope with the trouble to some extent and to prevent its universal spread. With this object in view, superintendents are now instructed to keep a close look-out for the first indications of disease; and expert plant-doctors entomologists and mycologists are maintained in all important tropical planting countries. It is their business to diagnose correctly any symptoms of disease which may appear, and to prescribe the most appropriate remedies which science has been able to devise.
And, just as in the case of human ailments, the general practitioner is relied upon for the treatment of well-known complaints, but the scientific specialist is called in where the cases are difficult to diagnose, so it should be in the case of plant diseases. For everyday work the planter is his own doctor, and a good planter should be familiar with the nature and treatment of the common diseases to which his crop is liable. The recognition of new diseases and the devising of appropriate remedies calls for scientific research by highly qualified specialists. No community of planters can regard itself as safe from the danger of new diseases which does not maintain a properly equipped establishment for research, headed by a scientific officer of the highest possible qualifications. Probably in no branch of commercial enterprise does the liberal treatment of science pay better than in planting.
Hitherto no disease of Hevea has assumed the proportions of a serious epidemic, and we have no reason for anticipating that a fate similar to that of coffee in Ceylon awaits this industry in any country where rubber is now cultivated. Minor ailments exist however in some variety, and it behoves the planter as well as the agricultural official to familiarise himself with the known symptoms of disease and with the simpler recognised remedies. He can then take immediate steps to prevent the wide extension of trouble from small beginnings; serious trouble is only likely to occur if unhealthy individuals are neglected. As prevention is better than cure, an elementary knowledge of the general principles of plant sanitation is even more important than a knowledge of special diseases.