174 Ustulina Zonata [Lev.) Sacc. on llevea Brasiliensis 



rubber, and it is impossible to urge too strongly the necessity for im- 

 mediate and strenuous measures to keep them under control. 



A further complication arises: during the last six months, serious out- 

 breaks of different manifestations of so-called Bark Canker have been 

 found in widely separated districts in Malaya. The important point in 

 combating diseases of renewing bark is that the trees should be assured 

 proper ventilation. The more light and air penetrating to the trees, the 

 less chance of epidemics of Bark Canker. If Bark Canker becomes general 

 in Malaya, thinning-out will have to be undertaken to the irreducible 

 minimum number of trees per acre commensurate with profitable working. 

 When estates are forced to this position, the menace of a bad attack of 

 root disease is obvious. 



A critical period approaches for the plantation rubber industry in 

 Malaya. No immediate danger promises though the menace of disease 

 becomes more prominent every year. Fungus diseases will, in the long 

 run, provide the limiting factor, preventing the expansion and hindering 

 the progress of the industry. The logical conclusion drawn from facts 

 as they present themselves is that if preventive measures are not im- 

 mediately adopted, fungus diseases may prove the ultimate ruin of 

 an industry, which with careful foresight and administration, should 

 smother all competitors for decades. 



The future policy to be adopted in Malayan rubber plantations must 

 be one of two : either 



(a) An attempt to keep the present plantations healthy as long as 

 possible, or 



(6) A re-planting scheme at an age between 20-30 years. 



The profits gained by a rubber plantation depend upon the average 

 yield of dry rubber per acre per annum. There is little evidence regarding 

 average yields to be obtained from a consideration of present day estates 

 approaching the age of twenty years, and that available is contradictory. 

 Some old areas yield remarkably well, while others give comparatively 

 poor yields. There are reliable records (6) of a thirty-seven year old tree 

 giving 392 lbs. 7 ozs. of total rubber in five years, a yearly average of 

 78 lbs. 8 ozs. There are also reports of old trees in Malaya giving enor- 

 mous yields, but these cannot be claimed to be authentic. There appears 

 no reason why plantation trees in Malaya should not approach the above 

 standard, and if such yields are possible the policy of rendering the 

 present plantations as permanent as possible should be adopted. At the 

 same time it will be advisable to move cautiously, for observations on one 

 estate, run on up-to-date lines, lead to the conclusion that the yields on 



