264 PHYTOPHTHORA MEADII n. Sp. ON HEVEA BRASILTENSIS 



The trees are 20 to 40 feet high, so that power sprayers -would have to he used, 

 ahd in order to set at each flower so much of the sohition would be used that 

 it would practically amount to spraying the tree. Besides it would be exceed- 

 inj^ly difficult to spray the upper parts of trees from the f]jround. as the side 

 branches of trees on most well f];rown estates touch and sometimes overreach 

 one another. The same applies in an increased degree to spraying the fruits, 

 as the stand of foliage is greater during the fruiting season. Spraying the fruits 

 of the areca-palm, Arena catecTin, with Bordeaux Mixture as a preventive 

 against the attack of Ph/fophfJwra arecce (Co^em.) Pethyb.. has been a marked 

 success. There, however, the fruits are aggregated in from 1 to 3 bunches on 

 the single stem just under the crown of leaves, and are comparatively easilv 

 accessible for spraying. Bordeaux Mixture would protect the fruits of Hevea 

 against Ph/tophthora just as effectively, but their scattered position on the tree 

 precludes its use at present for reasons of economy, while there is the additional 

 reason against its use in that even traces of a salt of copper in latex cause the 

 rubber to deteriorate, and it is almost certain that traces of copper would be 

 washed by rain into latex from spraved trees. The action of anv other 

 protective fungicide on rubber would have to be investigated before it could 

 be recommended as a spray. Besides in any extensive spraying operations the 

 difficulty of getting enough water to spray in the dry weather would be 

 great, and the cost of treating the higher portions of an estate would be very 

 high. 



The question whether it is not possible to prevent trees from flowering, 

 or to reduce the amount of flowering by some cultural means, has also been 

 considered. The Government Economic Botanist has discussed this with me 

 on estates, but it does not seem feasible. Horticultural endeavour has been 

 rather in the direction of increasing the flowering capacity of plants, and so far 

 as we know, there are no cultural methods of preventing a tree from flowering, 

 or reducing the number of flowers it produces that are applicable in estate 

 conditions. 



It seems to me that the only feasible methods of directly dealing with the 

 fungus are removing the dead branches and the fruits, and in 1917 four blocks 

 of considerable size, 100 acres in two cases, in widely separated parts of the 

 rubber growing area were set apart for experiment which consisted in destrov- 

 ing all old fruits and debris, in removing and destroying, shortly after the 

 season of periodic leaf-fall (practically in March and April), aM branches that 

 had died back, and in removing and destroying all fruits before the 1st of 

 June. This will be repeated in 1918, and will give data as to the cost and the 

 effectiveness of the measuiep undertaken in stopping or reducing the disease. 



