57 



Brooks obtained pure cnltm-es of the fungus, and carried out 

 inoculation experiments on the roots of healthy trees. These were 

 entirely unsuccessful and suggest that some condition adverse to 

 Hevea must exist before the fungus can enter living roots. This 

 condition may well be bad soil ventilation. Infection may be either 

 by spore infection on wounds (on exposed roots) or contact with 

 diseased jungle i-oots and precautions must be taken accordingly. 



UstuUna zonata. 

 A disease first detected in Malaya in 1914 by Brooks — followed 

 by Sharpies — the latter author attaches moi-e importance to the 

 manifestation.s of the fungus as a collar-rot than as a root disease ; 

 but root attacks and spread by contact should not be neglected. 

 Fetch attributes the prevalence of the disease in Ceylon on tea 

 to lateral root contact from stumps of G-revillea which had been 

 left in the ground. The characteristics of an TJstulina attack ai^e 

 — a dry rot of the attacked wood, and the pi-oduction of coarse 

 interlacing black lines in the wood. There is no external mycelium 

 and the wood must be cut into before the disease can be found. The 

 fructifications are of somewhat varied form — the most common being 

 a plate-like mass, adpressed to the collar of the tree — the colour of 

 which changes from yellowish-white, thi-ough grey — white and 

 greenish-grey to black. In the later stages, when splashed by mud, 

 -the fruits easily escape observation. More i-ai-ely other forms of 

 fruit body are found, e.g., a solitaiy stalked form ; stalked forms 

 aggregated to a plate ; and other lichen-like foi-ms. All, except the 

 last, produce spores in abundance, which falling or being canned to 

 wounds or cuts propagate the fungus. It follows that the fruit 

 bodies of this fungus, like those of Sphierostilbe, should be destroyed 

 as soon as found. 



Bbown Root Disease (Hymenochsete noxia). 

 So far this disease has not been recorded to any great extent in 

 Malaya although Fetch states that it is the commonest root disease 

 of Hevea in Ceylon. Characteristic of this fungus is the production 

 of hard, brittle, bi*own or black incrustation around infected roots — 

 composed of soil bound to the roots by the fungus mycelium. 

 Within the decayed roots are often found brown lines or plates of 

 fungus tissue. Diseased wood, at any rate in Malaya, remains hai-d, 

 but may become honeycombed. Fructifications are of very rare 

 occuiTence and are of no pi-actical importance. « 



So far as I know, no artificial inoculations have been attempted 

 with the fungus, but the disease can often be traced to a jungle 

 stump. Brown root disease has usually been considered as not 

 dangerous owing to its slow spread — the idea being that the attacked 

 tree dies, and is taken out before the roots of the surrounding trees 

 can be infected. This may be so, but it is better to be on the safe 

 side,, and to treat the disease like all other contact root diseases. * 



