302 



THE AGRICULTURAL NEWS, 



September 17, 1910. 



FUNGUS NOTES. 



SOME DISEASES OF RUBBER TREES. 

 PART I. 



As mention has been made, in recent numbers of the 

 Aijrirultural JVeu-s, of one or two diseases of Hevea, and as 

 the cultivation of this plant, as well as of Castilloa, has been 

 introduced into some of the islands, it is thought that a sum- 

 mary of the diseases to which ruliber trees are subject in the 

 different parts of the world in which they are grown, more 

 partii'ularly the far East, may prove of some interest to read- 

 ers. One peculiarity of the majority of these complaints is 

 their close similarity to those commonly found affecting cacao. 

 Not only are the external symptoms much alike on both hosts, 

 in several cases, but the causative fungi of the disease on each 

 are often closely related species, even if not actuall}' identical. 

 There is also a connexion, in one or two cases, particularly 

 with regard to root disease, between the species of fungi 

 found on Hevea and those on cocoa-nut palms ; more- 

 over, some of these on the former host plant also attack tea, 

 coflee, mangos, and certain other plants of economic 

 importance. 



ROOT DisE.ASEs. Two different important root diseases 

 affecting rubber plants are known, and one or two others have 

 been recorded as being occasionally found. To what extent 

 the minor ones are identifiable with one another or with 

 known diseases of other host plants is not yet definitely 

 known, as the fructifications of the causative fungi have not 

 been found. 



The best known root disease is probably that due to 

 Fames semitostus, Berk., which occurs in Ceylon and the 

 Federated Malay States. The fungus belongs to the order 

 Polyporaceae, of the Hymenoniycetineae. It attacks the main 

 root, or some of the lateral roots, of trees between the ages of 

 fifteen months and four years. In some instances in Ceylon, 

 the first indication of the diseased condition of the roots 

 was given when the trees were blown down by a high wind; 

 it was then found that the main root was destroyed, having 

 been eaten through by white ants, which had followed the 

 attack of the fungus. Strong lateral roots had been devel- 

 oped, which served to supply the trees with moisture, but these 

 were not strong enough to enable them to resist the wind. 

 More generally, however, the first symptoms are the browning 

 of the leaves round the edges and at the tips, owing to the 

 ringing of the main root by the fungus, which thus stops the 

 water supply. Three days later, the trees are completely 

 dead. No latex will flow if the stem is wounded, and in some 

 cases the leaves fall off". More usually, however, the tree is 

 blown down before this happens, especially if the roots have 

 been eaten by white ants. The fungus forms a whitish, 

 cobweb-like felt on the main root, and white strands, or cords, 

 on the lateral roots; the.se cords, when older, frequently 

 become straw-coloured. The roots appear black, the cortex 

 is soft and rotten, and no latex flows when it is cut. The 

 wood is discoloured, usually being turned brown. Fructific- 

 ations only appear on trees which have been dead some time, 

 or on jungle stumps. They are of a bracket shape, and occur 

 just above the ground level; their upper surfaces are orange, 

 or maroon-coloured, while the under ones are of different 

 shades of brown, being orange-coloured only when quite young. 

 The spores of the fungus can, apparently, only germinate on 

 dead stumps, and it is from these that the rubber trees are 

 affected. This accounts for the limitations in the age of the 

 hosts attacked, as, if the roots have not come into contact 

 with diseased jungle remains before the tree is four years 

 old, subsequent infection is unlikely. Although the infection 



always appears to occur in this way, the mycelium from 

 these stumps is capable of direct parasitism, and does 

 not require the presence of wounds to enable it to attack 

 its host. The remedial measures recommended are the 

 usual treatment for root diseases, combined with the 

 remo%al of all decaying stumps and roots from those 

 areas which are known to be infected. References to this 

 disease are: Circular's and Agricultural Jourjial of the 

 Royal Botanic Gardens, Ceylon, Vol. Ill, p. 237; Root 

 Disease of Hevea Brasiliensis, Petch; Bulletin No. 2 of 

 the Department of Agriculture of the Federated Malay States, 

 Gallagher; Ccijlon Adrninistration RejMrts 1905 and 1906, 

 Petch; A(/rict(ltural Bulletin of the Straits a7id Federated 

 Malay States, Vol III, p. 174, Ridley, with short notes in other 

 volumes of the same publication. In connexion with this 

 fungu.s, it is interesting to note that a white sterile mycelium 

 has been found to attack the roots of both Hevea and Castilloa 

 in Java, and that it is de.scribed by Dr. Bernard in Bulletin 

 XII du Departement de I'Agriculture aux Indes Neerlandaises. 

 The second important form is that known as brown root 

 disease. The external .symptoms are very similar to those 

 existing in the case of the first one, but on examining 

 the attacked parts, it is found that they are surrounded 

 by a mass of earth and stones so firmly bound on to 

 them by a fungus mycelium that they cannot be cleaned by 

 washing. This mass forms a felt of a white or yellow- 

 brown colour which is apparently fairly characteristic of 

 the disease. No fructifications have been observed, but the 

 fungus in Ceylon is believed to be identical with a form 

 provisionally referred to the genus Hymenochaete, found on 

 cacao in Samoa, and with that referred to as Spurvtrichum sp. 

 on cacao in .Java. It attacks cacao, Hevea, Castilloa, tea, 

 Caravonica cotton and dadap (Erythrina spp.) in Ceylon, 

 and also occurs in the Federated Malay States. Petch, 

 in the Ceylon Administration Reports for 1906, thinks it 

 identical with a fungus known as /;■/»(',(•_/?(;('(/«, Klotsch, which 

 attacks coffee, and Ridley describes a fungus which he also 

 believes to be Trjje.r flavus on Hevea, in the Malay States. 

 (Agricultural Bulletin of the Straits and Federated Malay 

 States, Vol. V, p. 64.) The coffee fungus was known to occur 

 in the Jlalay States, and the Hevea disease from the same 

 locality is very similar; it akso re.sembles a disease attacking 

 clove trees in Malacca. Irpex flams is reported, as well, 

 from Java, Queensland, and North America. The remedial 

 measures against brown root disease are the same as in the 

 case of Fames semitostus. 



In one instance, a root fungus with a white mycelium 

 produced fructifications recognized by Fetch as Poria vincta, 

 B. and Br. {Ceylon Administration Reports, 190.t). Recently, 

 a fungus on cacao and Hevea in Apia has been described by 

 Dr. Funk as Hynunachaete naxia, Henning, and may be 

 identical witli the Ceylon brown root disease, though this is 

 uncertain. A fungus also identified as Hymenochaete noxia 

 causes a disease of cacao in West Africa. These two 

 fungi conclude the list of parasites found on the roots. 



To summarize, then, there are two important root diseases 

 of Hevea. The first is found in Ceylon and in the Federated 

 Malay States, and is due to Fames semitostus, whose mycelium 

 is characterized by the formation of white or straw- 

 coloured cords on the lateral roots. The second occurs on 

 Hevea and Castilloa, in Ceylon and in the Malay States, 

 and may be designated the brown root disease. It is 

 characterized by forming a light brown felt of mycelium 

 mixed up with earth and stones, around the roots attacked. 

 A fungus similar to Irpex flavus is described from the 

 Federated Malay States, and is possibly the same as the 

 brown root disease fungus. Another form, identified as 



