VI 



RUBBER 191 



but lives in the excrement of scale insects which are 

 common on the trees, and interferes with the normal 

 physiological functions of the plant. 



RUBBER 



Cankers. Probably the most important diseases of 

 the rubber trees are the cankers, most of which are due 

 to the various species of fungi which belong to the 

 genus Nectria. They attack the trunk and branches, 

 and if not controlled will kill all parts of the plant 

 beyond the point of attack (see page 185). 



Nectria. One of the most common diseases of the 

 trunks of the rubber trees is a Nectria, which is 

 probably N. diversispora, Fetch. It attacks the Para 

 rubber trees of the Straits, Ceylon, and the East Indies, 

 causing them to become very much roughened and 

 swollen places to be formed on the branches and trunks. 

 On peeling the bark the tissues below are found to be 

 brownish or claret in colour. The branches lie beyond 

 the point of injury, and the vitality of the tree is 

 greatly reduced. Although the disease has no con- 

 nection with the roots it is usually much more severe 

 in low, poorly-drained soils than in high, well-drained 

 land. The fruiting bodies of the fungus are pink or 

 red in colour. They, together with the diseased parts of 

 the tree, should be cut and burned. It has been recom- 

 mended that close planting be avoided, and that Ficus 

 elastica be used as wind-breaks to prevent the distribu- 

 tion of the disease. 



N. diversispora also occurs as a saprophyte on dead 

 fruits. 



Nectria funtumia, Massee, is the cause of a canker 

 disease of the rubber tree (Funtumia elastica) of 

 Uganda. It attacks the trunk from four to six feet 

 above ground, causing the bark to become thickened, 

 cracked, and ragged. It has very much the appearance 

 of the large wounds caused by the " slime rlux." It 

 also very much resembles the Nectria canker of the 



