Mining in Malaya

1 <PLANT DISEASES AND PESTS SINGAPORE : Fraser & Neave, Limited, Printers. •923- Original from and digitized by National University of Singapore Libraries Original from and digitized by National University of Singapore Libraries Plant Diseases & Pests, of diseases and pests of economic plants THEinfollowingMalaya underaccountthreedealsheadings:—Fungoidwith the problems and Bacterial Diseases, Insect Pests and Methods of Inspection and Control. FUNGOID AND BACTERIAL DISEASES. The study of fungoid and bacterial diseases in their true relation to extensive cultivation is of com¬ paratively recent date, and it is only during the last two decades that the losses accruing to cultivators have been realised and approximately estimated. The extent of the losses caused by crop diseases is illustrated by the following figures given by various .authorities in America. (1) California Vine Disease in 1892 . .. G. $10,000,000 (2) Wheat Rust in United States 1898 . .. 67,000,000 (3) Wheat Rust in Illinois in 1885 .. .. 1,875,000 (4) Potato Late Blight in • New York 1904 .. 10,000,000 {5) Potato Blight in United States (annual) .. 36,000,000 Original from and digitized by National University of Singapore Libraries ( 2 ) Plantation Before proceeding to deal with specific Conditions in crop diseases of local interest, it may Relation to be instructive to indicate the chief Rapid Spread reason why plant diseases become of Diseases, more dangerous when a jungle tree, such as the rubber tree, is cultivated under plantation conditions. In the natural forests every tree is a survivor in the struggle for existence and only the hardiest individuals come to maturity. In the jungle, the mature trees or groups of trees of any single species are usually separated from the individuals of the same species by trees of widely differing constitution. Specialization or preference for one individual host, or at most a narrow range of hosts, is a well-known phenomenon in the case of parasitic fungi, so that, under jungle- conditions, a diseased tree may be found, but the fungus causing it cannot attack the neighbouring trees because their constitution is so widely different from that of the attacked tree. Plantation condi¬ tions are diametrically opposed to those of the jungle—the struggle for existence does not operate to the same extent, since each seedling plant has similar conditions and many comparatively weak individuals survive. The weak individuals may'be- attacked more easily by disease, and since each tree has a similar constitution to its neighbour, every single tree in the plantation may become infected- Plantation conditions, as a rule, favour rapid spread of disease and it is easy to realise that the greatest care is necessary in the case of the cultivation of a jungle plant taken from its native habitat. Diseases of Rubber. Prior to 1912 little definite research work had been carried out on the diseases of the rubber tree- Original from and digitized by National University of Singapore Libraries ( 3 ) During the last decade, however, many investigators have been engaged on disease problems wherever Hevea brasiliensis has been established on a large scale, so that our knowledge of the more important aspects of rubber diseases is now fairly extensive. It is important to mention here that information obtained in respect of diseases in one country does not necessarily apply, without modification, to other countries. Growth conditions in different countries may vary enormously, and this may influence the conclusions to be drawn from any research to such an extent that any recommendations may apply only in the country concerned. Any conclusions stated in this article must, therefore, be regarded as not necessarily applicable to countries other than Malaya. Rubber diseases in Malaya can be classified as:— (a) root diseases. (b) stem and branch diseases. (c) bark diseases. The above divisions are self-explanatory with the exception of (c). Bark diseases are so called be¬ cause they occur when the tree is tapped for the extraction of latex. The latex flows from the cortical tissues when a thin paring of cortex is excised by the tapping knife. The tapping is done at regular intervals, usually once per day or once every two days, and each tapping exposes a thin strip of tender tissue and forms a suitable place of entry for certain fungi. Bark diseases are, there¬ fore, diseases of the tapped surface. Root In dealing with root diseases, reference Diseases. must be made to the method of opening up the land previous to planting. Most Malayan plantations are started on virgin jungle Original from and digitized by National University of Singapore Libraries ( 4 ) land. The jungle trees are felled, leaving the stumps in the ground, and the luxuriant undergrowth is cut down. After a period of dry weather the timber and dried undergrowth over the felled area are fired. After the fire, the stumps and large logs, though much charred, still remain and during decay form suitable food material for fungi. The original source of the root diseases of Hevea brasiliensis can be traced to the jungle stumps and logs left on and in the ground. If the land were cleared thoroughly before planting it could be stated definitely that root diseases would be negligible on Malayan rubber plantations. The following root diseases have been investigated in Malaya:— FoTfies lignosus (semitostus). This fungus, causes most damage on young plantations with trees under seven years of age. Occasionally in localised areas it has caused considerable devastation. Most plantations have suffered loss from this disease; but since, owing to close planting, the trees have to be thinned out at the age of six or seven years, the loss caused by this disease has not, in the past, had serious consequences. The distinguishing characteristic of this fungus is the white external rhizomorphic strands running over the lateral roots of the tree. The fruit-bodies are remarkable in being persistently sterile, while similar fruit-bodies of closely allied species produce millions of spores, each capable of infecting' a healthy tree under suitable conditions. Spliaerostilbe repens. This fungus causes a root disease of rubber trees, of any age, growing in acid, water-logged soil, and Original from and digitized by National University of Singapore Libraries ( 5 ) is most common in the coastal areas. Occasionally this fungus destroys large areas of rubber but usually its action is slow and only individual trees are attacked. The more characteristic features are the flat, black, interweaving rhizomorphic strands, seen closely adpressed to the wood when the bark is removed from the diseased roots, and the fruits of the fungus which, when present, are typical though rather minute. The soil round the roots of an attacked tree and the diseased wood as a rule give off a most unpleasant odour when freshly dug up. Ustulina zonata. This fungus disease is wide-spread, and numer¬ ous cases can be found in many old plantations. The fungus is capable of attacking any part of the tree, i.e. root, stem or branch, if the wood is exposed. It often works in conjunction with boring beetles; the insects, after penetrating the wood, are followed by the fungus, and, in such cases, the trees are killed very rapidly. The fungus often enters the stem at places where large branches are broken off by the wind or other agencies. In all cases in which Ustulina- zonata is active in tissues of Hevea brasiliensis, the appearance is the same,—a typical dry rot of the woody tissues with numerous conspicuous black lines, running through the rotted wood. The disease is most com¬ mon on trees over eight years of age. Fomes pseudo-ferreus (Wet-Root Rot). The action of this fungus on roots of Hevea brasiliensis is very distinct from that of Ustulina zonata. Fomes pseudo-ferreus produces a typical " wet-rot," in whatever situation the attacked tree Original from and digitized by National University of Singapore Libraries ( 6 ) is growing. The disease is very dangerous on account of its subterranean habit, for an attacked tree usually blows over before the disease appears above soil level. When a tree is found attacked by this fungus .it may be assumed that a number of neighbouring trees are also affected. This disease has caused large losses on many of the older planta¬ tions, but is seldom found on young trees. The wet-rot of the freshly-dug roots together with the inconspicuous brownish lines in the attacked tissue serve to diagnose the attacks of this fungus. Brown Root disease. This is hot a common disease on rubber but the appearance of attacked roots is quite typical. The mycelium of the fungus binds up earth and stones in the immediate proximity of the roots to form a firm encrusting mass, which is detached with difficulty. The Brown Root disease is a common feature in other tropical cultivations, e.g. tea, coffee, camphor, which will show similar symptoms. This disease is under investigation at the present time, but little definite information has' been ob¬ tained. In these diseases, control measures take the form of preventing the spread of the disease by trenching round the affected areas, removing and burning dead wood, and applying lime before supplying. Stem and Only two stem and branch . diseases Branch require to be mentioned, viz. Pink Diseases. disease and Die-back disease. Pink. Disease. This disease is caused by a fungus known as Corticium salmonicolor, which on Hevea brasiliensis shows varied manifestations.. Prior to 1912 the Original from and digitized by National University of Singapore Libraries ( 7 ) ■disease was common in only three small centres but in 1913-14, it assumed epidemic form, and spread rapidly, practically throughout the whole Peninsula. The name, Pink Disease, is associated with the ■commonest appearance, a continuous pink incrusta¬ tion covering the attacked branches.

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