CHAPTER VII. 

 PEStS. 



CONDITIONS WHICH FAVOUR THE SPREAD OF DISEASE. 



NOTHING is more favourable to the spread of disease than the 

 practice which now obtains of planting large areas with a single 

 product. 



Where large areas of a permanent crop such as rubber are 

 cultivated, the difficulties attending the prevention and exter- 

 mination of disease are far greater than in the case of an annual 

 crop, for with the latter a change of crop will invariably produce 

 these results. It therefore behoves the Para rubber planter to 

 be constantly on the alert with a view to discover disease in its 

 early stages, and take immediate steps to eradicate it. Investi- 

 gate the aetiology of a disease, remove the cause, and the ill- 

 effects will be removed with it. Fortunately, none of the 

 numerous fungus and insect pests of Hevea have, as yet, caused 

 serious damage, but it should be borne in mind that, with a 

 comparatively few exceptions, the cultivation of this product is 

 of quite recent date. The advantages likely to accrue from the 

 cultivation of between-crops with Para rubber have already been 

 pointed out. In place of, or preferably in addition to these, belts 

 of unrelated trees or plants should be grown for the purpose of 

 dividing up large areas of Hevea with a view to still further 

 check the spread of disease. 



Since it generally happens that a specific disease confines its 

 attacks to nearly allied species, the plants chosen for the between- 

 crops and the disease-checking belts should be selected from 

 those belonging to different natural orders of plants from that to 

 which Hevea belongs, viz., Euphorbiaceae. For economic reasons 

 the plants chosen should yield commercial commodities. Those 

 suitable for between-crops have already been dealt with. For 

 the second purpose there are several rubber-producing trees 

 which are admirably adapted, such as Castilloa elastica, Cerv., 



