238 



THE AGRICULTURAL NEWS. 



July 22, 1911. 









[■/■■.■-';5ia. 



FUNGUS NOTES. 



THE SEREH DISEASE OF THE 



SUGAR-OANE. 



The disease which forms the subject of the present 

 article has long been known in .Java, from which island it 

 was first reported in 1882, though there is reason to believe 

 that it occurred there as early as the year 1875. It has 

 spread steadily and regularly there since the first observation 

 of it, the direction of its progress being from west to cast. 

 There is, however, one peculiar limitation that has been 

 observed in connexion with its spread, namely, that it never 

 appears on canes growing at a high elevation, even though 

 such localities are unsuitable to the plants in other respects. 



Although much work relating to this disease has been 

 conducted by several well qualified .Mycologists, yet its actual 

 cause is still very obscure, and none of the theories put for- 

 ward on the subject can be said to have been at all definitely 

 established. Moreover, although its symptoms are numerous, 

 it is only in serious cases that all of them appear; often only 

 a few of them are present with certainty. As a consequence 

 of this, there is considerable doubt as to the number of coun- 

 tries in wliich the disease e.xists throughout the tropics, and 

 a certain amount of confusion has arisen between this and 

 other diseases. This question, which is of some importance, 

 will be dealt with below. 



According to an article by Maublanc, which appears in 

 L'AiJrindtiire Pratique des Pai/s Chanils, No. 91, p. 313, the 

 most characteristic symptom is the shortening of the inter- 

 nodes of the stalk. This results in a very peculiar appearance 

 of the diseased plant: the leaves are crowded together, and the 

 young blades at the tup of the stem open sooner than they do 

 on normal plants, and .spread out in the shape of a fan, 

 instead of remaining for some time rolled up in a cylinder. 

 The leaf blades are reduced in size and marked with lines of 

 a yellowish green colour. Portions of them die and dry up. 

 In addition to this, there is generally an abnormal develop- 

 ment of the buds at the base of the stems, so that the latter 

 become much branched. This is accompanied by a profuse 

 production of roots, causing infected stools to present an 

 appearance that is very dillorcnt from that of those which 

 are healthy. In fact, the attacked canes clo.sely resemble the 

 grass {Andropoijon Schoeiunit/nix) yielding lemon grass oil, 

 which is common in .Java, and known to the natives as 

 'sereh'. It is from this resemblance that the disease is said 

 to have taken its name. 



Besides the abnormalities which occur in the stem and 

 leaves, sereh is often characterized by the presence of dis- 

 eased roots on the canes. The tips of these are frequently seen 

 to be dead, while in more serious cases the roots atrophy almost 

 entirely. Another indication of this, as of other diseases of the 

 sugar-cane, is that attacked plants have a marked tendency to 

 arrow. 



Although most of these symptoms are present in serious 

 cases of the disease, yet in many instances there is a large 



variation from the typical appearance. The canes may attain 

 a considerable size, but possess short joints in their upper 

 parts; they are surmounted by a fan-shaped crown of leaves, 

 while below, short branches are produced from the buds. 

 All stages of alteration in appearance may occur- -from the 

 stunted and peculiar stools presenting the appearance of sereh 

 grass, to stools having general characters very little different 

 from those of healthy canes. 



There are a few other external symptoms that may be 

 present, among which the following may be mentioned. The 

 nodes may be tinted red, and the growing portion of the 

 stalk is often of the same colour; while the leaf .sheath and 

 the root origins become vermilion in colour. In some cases, 

 there is no formation of wax on the stem and in some 

 instances the leaf sheaths may stick to the stalk. 



When a diseased stem is split open, it is seen that the 

 tissues are considerably disorganized. The vascular bundles 

 are filled with a quantity of gum, which completely blocks 

 the cavities of the vessels. The position of the bundles is 

 marked by a red discolouration which is most easily seen at 

 the nodes, but often extends into the internode in the form 

 of a narrow, red streak. Disorganization of the vascular 

 bundles is also observable in the leaves No gum is, however, 

 formed in the diseased roots. 



There are two theories as to the origin of the disease. 

 According to the first, it is physiological, and due to unfavour- 

 able conditions of soil and climate, to want of proper tillage, 

 or to the employment of unsuitable manures. The bulk of 

 the evidence, however, is against this theory, as the disease 

 would appear to be infectious. This is indicated by its 

 method of spread in Java — by the fact that when it first 

 appears in a field it does so in spots, which increase in area 

 from year to year, and from the further fact that diseased 

 cuttings, when planted, either rot or give rise to diseased 

 canes. According to the second theory, it is an infectious 

 disease due to a specific parasite, but opinions vary con- 

 considerably with regard to the nature of the parasite. The 

 disease has been attributed to the attacks of nematode worms 

 on the roots, to the presence of a fungus in the tissues, as 

 well as to the action of bacteria. The eel-worm theory of 

 its origin is not now generally accepted, that having the 

 greatest degree of probability being its attribution to the 

 presence of bacteria. 



By way of remedial measures, it is recommended that 

 only thoroughly healthy cuttings should be planted, and that 

 these should be taken from health)- canes grown on soil where 

 the disease has not made its appearance. .Much has also been 

 done in Java in this respect in obtaining seedling canes more 

 or less inunune to the disease, while attention may again be 

 called to the success which has accompanied the planting of 

 healthy cane cuttings, produced in spei:ial nurseries in the 

 mountains. 



As will have appeared from the account of the symptoms 

 as given above, this disease may be easily confused with one 

 or two others. That for which it is most frequently mi.staken 

 is gummosis — a malady definitely known to be due to a bac- 

 terium, P.fctidomoiias vascitlariuu, Cobb. In some respects 

 also, it possesses symptoms resembling those of root disease, 

 as for example, the fan-shaped .arrangement of the leaves, the 

 presence of dead roots, and of others dead and discoloured 

 at their tip.s, as well as the large number of these that are 

 developed. (.)ther points of resemblance are the stunted 

 appeariuice of infected stools, and the fact that the leaf- 

 sheaths may adhere to the stem Consequently, great care 

 requires to be exercised in determining this disease in any 



