5 



Saps and Exudations. 



We may, therefore, conclude that as far as the root and foliar developments 

 are concerned, there are no serious objections to the original planting of Para 

 rubber trees ten feet apart. But such a distance is far too close for mature trees 

 and can only be recommended on the understanding that the estates will be thinned- 

 out after the fourth or fifth year. I must, however, remind you that many of our 

 30-year-old trees are growing well, though they are only eight to ten feet apart. 



SPREADING OP DISEASES. 



When, however, we come to the question of the spreading of diseases, a 

 subject on which I would prefer the entomologist or mycologist to inform you, 

 I think we are all prepared to admit that an epidemic would spread much more 

 rapidly on a densely planted estate than on one with fewer trees ; no matter 

 whether the disease was on the leaves, stems, fruits or roots. Furthermore, the 

 close planting of trees is only possible when thinning-out is intended ; this means 

 killing the trees ; and if dead stumps are left behind, perhaps assisting in the spread 

 of root disease. The Para root disease, as most of you already know, commences 

 as a fungus on the stumps of trees in your clearings, and by means of slender threads 

 spreads along dead roots, through the soil, to the living roots of the rubber trees. 

 It may be argued that the differences in distance between trees planted ten and 

 twenty feet apart are so insignificant when one considers the vitality of the diseases 

 and their power to spread, that it may be disregarded as an objection to close 

 planting; while I am prepared to admit that there seems some reason in this, I 

 cannot omit to emphasise the necessity to uproot all dead stumps, whenever 

 possible, on estates where closely planted trees have been purposely killed by 

 tapping. It should be remembered that no matter how far apart your trees are 

 planted, the same root disease may appear on stumps left during clearing operations 

 and even widely-planted estates be seriously affected. The disease appears on most 

 rubber properties which have been planted on virgin land on account of the 

 abundance of large tree stumps, and is therefore not confined to closely-planted 

 estates. 



ADVANTAGES OF CLOSE PLANTING. 



So much then for the arguments against close planting. Now let us consider 

 the other side. The advantages of preventing wash and exposure of our Ceylon 

 soils are only too fully recognised, and I propose to consider a more serious point, 

 i.e., the available tapping area. Every tree, having a circumference of twenty 

 inches at five feet from the base, presents an available tapping area of 1,200 square 

 inches. If you: work out this point in connection with the number of trees per acre, 

 when planted from ten to twenty feet apart, you will find that at the end of the 

 fourth or fifth year, an estate planted 10^10 feet has an available tapping area of 

 522,000 square inches, per acre, whereas one planted 20 x 20 feet apart has only 130,800 

 square inches, or approximately only one-quarter of the closely-planted one. This 

 is the great outstanding advantage of close planting, and I would ask you to fully 

 consider what it means during the fourth, fifth, and sixth years. It is, as you know 

 with tea and coconuts, much easier to thin out a closely-planted area than to 

 subsequently interplant a widely-planted one ; and when one considers the results 

 obtained with other plants, I do not see why the remaining Para rubber trees 

 should not ultimately make satisfactory progress on closely planted estates which 

 have been systematically thinned out. On any rubber property there is always 

 a proportion of the trees which do not thrive as well as the others, and this is the 

 more serious the fewer the trees on the estate. On an estate closely-planted, the 

 intermediate trees could be killed out in a definite manner until 200 or 250 trees 

 per acre remain after the 8th year. It is almost certain that the yield of rubber 

 obtained by making rubber its own catch crop will pay for the complete removal 

 of all dead stumps and leave a balance of profit worth considering. 



