86 



NATURE 



[March i8, 1920 



the English Channel and in the Bay of Biscay and to 

 the west and south. The chief fish of this region 

 are the migratory mackerel and pilchard and the 

 hake, which apparently is a great wanderer. It is 

 hoped also to investigate the possibilities in respect 

 to tunny, of which there should be an almost un- 

 limited supply in the Atlantic. France undertook the 

 preparation of a fishing chart of certain grounds, 

 Ireland particular cruises to meet the French vessel, 

 and England to continue and extend her investigations 

 into the waters of the Channel. England was also 

 asked to undertake, as soon as possible, regular 

 cruises to the south-west to investigate the approach 

 of the Gulf Stream waters in respect to mackerel, 

 pilchards, and tunny. 



At the full meeting on Saturday, March 6, the pro- 

 grammes of the committees were adopted, and Mr. 

 H. G. Maurice was unanimously elected president for 

 the ensuing- year, the next meeting to be held in 

 Copenhagen in 192 1. The present writer believes that 

 the fishery industry appreciates the vital importance 

 of these very technical investigations, in the results 

 of which the interests of the fisherman and the re- 

 searcher are identical ; he appeals to the industrv to 

 co-operate in every way in its power, and in par- 

 ticular to return drift-bottles and marked fish. 



Exhibition of Diseases of the Para Rubber- 

 tree. 



A N important exhibition illustrating the fungal 

 •^"^ diseases to which the Para rubber-tree {Hevea 

 brasiliensis) is subject in Ceylon and Malaya was 

 opened on March 10 in the Botany Department of 

 the Imperial College of Science and Technology by the 

 Marquess of Crewe in the presence of leading repre- 

 sentatives of the rubber trade. The exhibition, which 

 has been organised by Prof. J. B. Farmer, Director 

 of the Biological Laboratories of the college, includes 

 a large number of trunks of rubber-trees, specially 

 shipped from the East, showing the diseases as they 

 occur in the plantation, and forms a striking com- 

 mentary on the optimism which obtained in the first 

 years of the industry as to the probable relative im- 

 munity of Hevea from disease. 



The warnings issued by botanists at the time that 

 the Para rubber-tree would no more escape epidemic 

 fungal disease than any other crop plant has, unfor- 

 tunately, been justified by events. At the present time 

 there are several diseases which, if not checked as the 

 result of sound scientific knowledge, intelligently 

 applied, may seriously afTect the future of the planta- 

 tion industry. The former optimism finds a present- 

 day counterpart in the equally dangerous view held in 

 certain quarters that "sanitation " is all that is neces- 

 sary as a safeguard against disease, and that, in con- 

 sequence, expenditure on mycological research is waste 

 of money. The fact that the causative organism (if 

 organism it be) of the most dangerous disease in the 

 plantations at the present time ("brown bast") is as 

 yet unknown is sufficient reply to so short-sighted a 

 view. The exhibition comprises three main sections : 

 (i) A series of rubber trunks affected by the chief 

 diseases met with in the East, illustrated by admirable 

 coloured wall-pictures of the diseases in situ; (2) cul- 

 tures and microscopic preparations of living fungi 

 isolated at the college from the trunks exhibited; and 

 (3) a section devoted to the important bearing of a 

 knowledge of the anatomy of the bark of the tree 

 upon questions of latex yield. This section also in- 

 cludes trunks illustrating different systems of tapping. 

 All the exhibits are accompanied by explanatory labels. 



The principal diseases represented are as follows : 

 NO. 2629, VOL. 105] 



(i) Broxvn Bast. — This is by far the most important 

 disease at the present time, and is rapidly increasing, 

 certain estates in Java having as many as 60 per cent, 

 of the trees attacked. It is an affection of the bark 

 in the tapping area, and is of acute importance, since 

 it quickly results in the complete cessation of latex 

 flow. Later, the bark becomes discoloured and burrs 

 appear over the affected area. The disease is met with 

 on young and old and on vigorous and backward trees, 

 and occurs in every type of soil. At present preven- 

 tive measures are confined to disinfection and excision 

 of the affected tissues, but successful treatment is 

 hindered by ignorance of the real nature of the disease. 

 Hitherto physiological disturbance produced by tapping 

 has been held to be the cause, but recent work in 

 Sumatra suggests a bacterial origin. Further research 

 alone can settle this fundamental question. 



(2) Fomes lignosus.- — Next to brown bast this is the 

 most serious disease of Hevea. It is a fungus of the 

 familiar Polyporus type, attacking the cortex of the 

 roots. In cases where it was neglected in the early 

 stages it has since wiped out large blocks of rubber, and 

 from the nature of the disease the replanting of such 

 areas has been impracticable. The mycelium spreads 

 to the Hevea roots from old jungle stumps, or from 

 soil in which old jungle roots have been lying. From 

 the infected Hevea roots it passes to all healthy roots 

 in the vicinity, finally destroying the trees. Treat- 

 ment consists in exposing the root-system and paint- 

 ing the diseased roots with Bordeaux mixture or 

 other fungicide. The soil is also heavily limed to 

 destroy the mycelium invariably present in it, and the 

 whole infecttxi area isolated by a trench. 



(3) Fomes pseudoferreus (Poria).— This fungus pene- 

 trates deeply into the wood of the Hevea roots, often 

 leaving the cortex as a living cylinder until the wood 

 is destroyed by a "wet rot." The tree thus shows 

 little external signs of attack until the disease has 

 reached the final stage. In consequence, measures of 

 dealing with Poria are limited to preventing its spread. 

 The treatment adopted is essentially the same as for 

 Fomes lignosus. 



(4) Dry Rot {Ustulina sonata).— This fungus is a 

 wound parasite, and gains entrance via lesions on 

 roots, stems, and branches, killing the wood, which 

 becomes soft and tindery. Owing to former neglect 

 of wounds, the disease is greatly increasing in older 

 plantations. The best preventive treatment is a 

 periodical dressing of all wounds with tar. When 

 confined to the branches the disease may be removed 

 by pruning, but if on the base of the trunk or on the 

 roots, the tree is usually found to be infected witli 

 Fomes in addition, and treatment is impracticable. 



(5) Patch Canker (Fhytophthora Faberi).— This 

 disease is increasing in all the rubber-growing countries 

 of the East. The bark just below the surface becomes 

 claret-coloured, and eventually dies off in patches. 

 The disease can be controlled by early rernoval of the 

 bark and coating the exposed surface with tar. but 

 the chief difficulty is that the affected bark is freely 

 entered by boring beetles which penetrate deeplv into 

 the wood, carrying with them spores of dry rot 

 (Ustulina). In consequence, nearly every case of 

 neglected patch canker is also infected with dry rot. 



(6) Stripe Canker (Phytoi)hthora 5/).).— This tanker 

 was a formidable menace during 1915-17, more than 

 70 per cent, of the trees in tapping on some estates 

 bein^- attacked. The disease first appears as narrow 

 vertical strioes just above the newly tapped bark, 

 and if tapping is continued during the wet season 

 the whole of the tapping surface rots away. For- 

 tunately, it is now almost completely preventable by 

 daily disinfection of the tapping cut. 



(7) Pink Disease [Corticium saJmonicolor) has 



