W. MCRAE 267 



season, would probably be the most suitable form. It must not be so tight 

 round the tree that translocation through the bark is retarded, and it must 

 be tight enough above the tapping cut to prevent water percolating between 

 it and the bark on to the tapped surface. The latter is the more difficult 

 condition to satisfy, but if the bark is smoothed and very slightly grooved, it 

 has been found possible to tie the " collar " on tight enough and seal the 

 intervening space with tar. The diffi.culties are obvious, and make-shifts will 

 have to be made to get over them till more normal nies, when timanufacturers 

 can turn their minds to the production of some suitable device. 



General measures with regard to estate ventilation will also indirectly 

 help to reduce the amount of damage caused by this and other bark-diseases, 

 and this, of course, is the immediate and main concern of preventive work. 

 Most estates in South India were closely planted, and the trees are now beinf 

 thinned out to between 80 to 100 per acre. Lower branches, especially those 

 that hang downwards, should also be cut off, and this will give a larger, freer 

 air space, and allow more Ught to get around the stems, and so ensure that the 

 bark grows and renews in more healthy conditions. Sooner or later, however, 

 the crowns of the trees will develop till they come close together, and form a 

 more or less continuous canopy of leaves, so that, after thinning, preventive 

 measures appHed to the bark are still as necessary. That gangs of specially 

 trained coolies are necessary on estates for efficiently carrying out measures 

 against diseases is generally recognized, and in South India we have gone a step 

 further by providing at the Agricultural College, Coimbatore, for writers who 

 are to supervise those " pest gangs," a simple course in plant-diseases ^^^th 

 special reference to diseases of Hevea, and one day I hope to attract young 

 planters to the College for short courses on diseases of planters' crops. 



Occurrence of fruit-rot, leaf-fall and bark-rot in 

 other countries. 



In 1908 Fetch' described a fruit disease of Hevea, and in 1910- gave a fur- 

 ther description and stated that it was determined to be due to Phytophthora 

 in 1905, in which year it occurred on an epidemic scale. He also records the 

 fact that after the fruits have rotted, the green branches may also die back, 

 and suggests that Phytophthora is the cause. He describes the claret-coloured 

 canker, and gives the result of inoculations with P. Faberiixom cacao pods on to 



1 Fetch, T. " Die Pike von Herea hrasiliensig." Zeitschr. fur Pflanzenlr., XVIII, pp. 110—91, 



1908. 

 ■i „ " Cacao and Hevea Canker." Circ. and Agric. Jouni. oj tfie K. B. G., Ceylon, 



V, pp. U3-1S0, 1910. 



