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Sharples (A.). UsUtlina zonata (Lev.) Sacc. on Hevea brasiliensis. — 

 Ann. App. Biol, Cambridge Univ. Press, iv, no. 4, March 1918, 

 pp. 153-178, 6 plates, 1 text-fig. [Received 3rd May 1918.1 

 Rubber trees on Malayan plantations have hitherto been remark- 

 ably free from insect and fungus troubles, and in consequence 

 no great attention has been paid to combating them. The 

 Scolytid beetle, Xyleborus parvulus, was first observed attacking 

 rubber in Malay in 1909, in one district only where many trees 

 had been pollarded. The method of planting rubber trees neces- 

 sitates the cutting out of large numbers when they reach the 

 age of 6 or 7 years and during the thinning, attacks by boring 

 beetles on the permanent trees become prevalent, and.it was found 

 that fructifications of the fungus occurred on the surface of the attacked 

 parts. Evidence indicates that there is a close connection between 

 attacks by boring beetles and Ustulina zonata. After fires on several 

 estates boring beetles quickly entered the bark of damaged trees, 

 and while these attacks were quickly followed by fungus disease, 

 in no case was the fungus found in trees where the borers were entirely 

 absent. As an experiment, the bark of 24 rubber trees was scraped 

 and five of these were cjuickly attacked, three by borers. Two of 

 these showed traces of Ustulina zonata in the bark five weeks after 

 the insects had entered. It was observed that the borers disappeared 

 after the first fortnight. This experiment showed that the important 

 protective layer in rubber trees is the outer layer of corky cells and, 

 if this layer is injured, attacks by boring beetles quickly follow. The 

 first borers attempting an entrance were trapped in the streaming 

 latex, but later arrivals succeeded in entering through places prepared 

 by their predecessors. During the process of thinning out, falling 

 trees come in contact with and bruise the branches and trunks of 

 neighbouring ones, wounding the outer corky layers, and through 

 these wounds the borers enter, being quickly followed by the fungus. 

 It is possible that borers may directly transfer fungus spores to the 

 trees they enter. Such insects as termites, ants, etc. walking over 

 spore-producing fungi would carry away numerous conidia or ascopores 

 attached to their appendages, and fructifications in the conidial stage 

 have been found showing traces of insect markings on the surface. 

 The function of termites in this connection appears to be of minor 

 importance, as the number of trees attacked by them and by U. zonata 

 is small compared with those attacked by borers and the fimgus or the 

 number of old trees suftering from fungus attack only. 



U. zonata is largely responsible for the death of trees attacked by 

 the borers, which would not in themselves be a serious trouble. It is 

 therefore obvious that strict attention must be given to all trees, 

 stumps or logs in which borers are working. These should be immedi- 

 ately cut out and destroyed, as they represent one of the worst sources 

 of infection. All trees scorched by fire should be carefully watched, 

 and, if borers attempt to enter, a coating of tar (80 per cent.) and crude 

 oil (20 per cent. ) should be apphed to the scorched surfaces, a second 

 coating being given if possible. Scorching of the high branches is 

 less easily dealt with, but these are not apparently much attacked by 

 insects, and in any case they can be readily cut away from the main 

 stem. Clearing the ground of rotting timber and the treatment of 

 jungle stumps will largely prevent trouble from termites. 



