RUBBER 597 



that the encrusting mass appears black instead of brown. 

 On cutting into the diseased root it is usually found to 

 be traversed by black or brown plates, and in the case 

 of tea the decayed wood may exhibit a honeycomb 

 structure. 



The fungus to which this disease is attributed, Hymeno- 

 chsetc noxia, was originally discovered in Samoa on bread- 

 fruit trees. Subsequently it was found on coffee in Java 

 by Zimmermann. In 1905 it was first recorded as parasitic 

 on Hevea in Ceylon, and since then it has been found to 

 attack, in the same country, cocoa, tea, dadap (Erythrina), 

 Castilloa elastica, Caravonica cotton, camphor, Cinna- 

 momum Cassia, Erythro.ry Ion Coca, Bran felsia americana, 

 Gremllea robusta, Codiceum variegatum, Ceara rubber, 

 etc. Brick has recorded it again from Samoa, where it 

 is known to attack cocoa. Castilloa, bread-fruit, and 

 Albizzia stipulata, as well as jungle trees; and specimens 

 have been received from the Gold Coast on Funtumia. 



As will be evident from the foregoing list, the fungus 

 is practically omnivorous. Yet the actual damage in each 

 case is usually strictly limited. Its growth in Ceylon is 

 very slow, and if the plant first attacked is removed as 

 soon as the disease is discovered, no further deaths occur 

 in that spot. Bancroft records the same slow growth in 

 Malaya. But it would appear from the records to spread 

 more rapidly in Samoa. Instances of its slow progress 

 when allowed to run unchecked have been noted in the 

 case of both tea and rubber; in one instance three Hevea 

 trees in a line were killed in four years. 



The fungus apparently spreads from one plant to the 

 next only if the roots are in contact, but even this does 

 not generally occur unless the dead plants are allowed 

 to remain for a fairly long time. An exception to this is 

 general in the case of Grevilleas in tea plantations, where 

 the Grevilleas are first attacked; in such cases a number 

 of tea bushes may be killed before the Grevillea dies. 

 Anstead has recorded an experiment in which a diseased 

 root was buried in contact with the roots of a healthy 

 tree, with the result that the latter was infected and died. 



The experiment of replanting a tree of the same species 

 in the place where one had just died from brown root 



