In a well lighted plantation which is kept clear of decaying stumps and branches, fungus diseases are not likely to make their appearance except sporadically. Close planting and the presence of intercrops produce conditions favourable for the introduction and spread of stem and leaf diseases, whilst decaying stumps remaining in the soil constitute a fruitful source of fungus diseases of the roots. Petch, in fact, goes so far as to state that if there were no dead stumps there would be no root diseases either in Hevea or tea. The conclusions to be drawn from these facts are obvious, but-they apply mainly to the precautions which ought to be taken during the first opening up of the estate. We have now to consider the sanitation of an estate in bearing.
On well managed plantations a special gang of labourers is often employed, whose business it is to make the circuit of the estate and to keep a close look out for the appearance of disease. This periodical inspection is specially necessary in districts subject to the attacks of die-back and pink disease, since these maladies may readily escape the attention of the tapping coolies. In such districts the removal of dead branches should constantly be carried out as fast as death overtakes them, and by this means the spread of the diseases may be reduced to a minimum. The pruning of lateral branches should always be done by means of a clean cut flush with the surface of the parent stem, in order that no projecting portion may be left to die back and offer a point of entry for disease germs. All extensive areas of exposed wood should be covered with tar. For this purpose ordinary gas tar is preferable to Stockholm tar. All branches and debris removed in pruning should at once be burned.
For dealing successfully with plant diseases, intelligent cooperation is eminently desirable. A single neglected and diseased property may constitute a serious menace to the health of the products on all the other estates in the same district. The case of an owner who is not amenable to the principles of cooperation in the treatment of diseases would constitute a strong argument in favour of coercive legislation. For the owner who neglects to take ordinary precautions for preventing the spread of disease is interfering with the rights of his neighbour almost as much as if he were to set fire to a corner of his plantation.