CHAPTER XVII. 

 DISEASES OF PARA RUBBER TREES. 



Diseases of plants grown on small areas — Epidemics over large acreages 

 — Cheeking disease by tree belts— Illustration showing hardy 

 characteristics of Hevea brasiliensis -Para rubber pests in Brazil 

 and Java — Leaf diseases of Para rubber — Fungi. Helminthosporium, 

 Periconia, Cladosporium, Macrosporium, Pestalozzia, Cercospora — 

 Preventive measures — Insects, plant-sucking bugs, weevils, and 

 mites — Preventive measures — Fruit diseases of Para rubber — Fungi, 

 Xectria and Phytophthora— Preventive measures — Stem diseases of 

 Para rubber — Fungi on old steins and green twigs — Preventive 

 measures — A bark fungus in the Si raits -Insects, wood-borers, ants, 

 and slugs — Preventive measures -Hunt diseases of Para rubber— 

 Fungi in Straits and Ceylon — Fomes in the Straits — Polyporus 

 Helicobasidium and Hymenochsete — Insects, termites, cockchafers, 

 grubs — Preventive measures — A disease on prepared rubber — 

 Probable causes and preventive measures -Analyses of black and 

 yellow tacky rubber — Chemical analyses of tacky and sound rubber. 



IT is often relatively easy to successfully grow a small number of 

 plants in any particular district without their suffering from the 

 ravages of innumerable insects and fungi. But if the same crop is 

 grown on a large scale matters often take a different turn. It has 

 frequently been my experience when dealing with minor pro- 

 ducts on a small scale to find that the diseases to which they were 

 subject never developed to a serious extent, but when once the 

 product was greatly extended the insignificant diseases became a 

 serious menace to the plants and often rendered further cultivation 

 impossible. 



It would appear on Oral considerations that any pest, which 

 found a desirable means of sustenance on the tissues of a particular 

 plant, would increase to such an extent that the few host plants in 

 the neighbourhood would be exterminated. But, for some reason 

 or other, many pests do not appear to behave in this manner, and it 

 is only when the host plant occurs in large numbers and over exten- 

 sive areas that anything like an epidemic is noticeable. 



Perhaps the occurrence in large numbers of the host plants in widely 

 separated districts ensures that the pests will find the requisite 

 means of sustenance, no matter where they occur, and their pro- 



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