Jan. 1907.1 



31 



Plant Sanitation. 



order to germinate, a number of conditions have to be favourable to allow of 

 extension to new trees." I t may be pointed out that in the allied species, Phytoph- 

 tliora, the spores are produced in abundance, and that the film of moisture on 

 a cacao pod suffices for their zoospores. 



" Dissemination may be brought about in several ways. Withering of 

 the head may expose the inner sheaths where most of the spores are produced, 

 or some of the latter may occasionally form on the outer lav er. aud in either case 

 they would be carried about by the wind. lusects might very easily carry 

 infection should they gain access to the spore-bearing mycelium, on the surface 

 of the spots. Infection may also be carried by the knives of the toddy-drawers 

 since each tree is climbed every year either to draw toddy or to cut the leaves. 

 In all these cases the danger is lessened by the fact that the spore formation 

 occurs usually between the inner layers of the bud, and this probably accounts 

 for the slow spread." 



The measures suggested deserve full quotation in view of the interest 

 aroused in the prevention of plant diseases by the recently proposed "Pest Ordi- 

 nance" in Ceylon. Apparently India obtains the desired result without a Pest 

 Ordinance. 



" The suggestions which I should make for an organised campaign against 

 the disease are as follows. Their carrying out will necessitate the formation of a 

 special staff for the purpose, for it is certain that at first, at least, the villagers 

 will be be slow to take measures for their own protection. If, however, the results 

 bear out the value of the work, real co-operation may be expected before long. 

 A number of expert palm climbers (such as toddy-drawers; should be selected under 

 the charge of an agricultural inspector or some similar official and provided with 

 small axes. They should be instructed to climb all diseased trees, both those in the 

 early stages and those already dead, and to cut off the green tops below the 

 swelling of the leaf sheaths. It is particularly essential that all trees in the early 

 stages should be dealt with, and these can be recognised where the villagers 

 themselves are unable to do so, by the whitening of one of the leaves towards the 

 centre of the head. After cutting off the heads the whole of the tops should be 

 collected into a heap in each village aud burnt. In this way, every dead or attacked 

 palm in a selected area should have its power of spreading infection destroyed 

 by burning the diseased parts, aud this measure alone, if steadily pursued, is certain 

 to give good results. The infectious matter is confined to the head of the palm, and 

 as the tree is doomed once the disease appears and will yield little or no further 

 profit, its removal costs little but the actual expense of labour in cutting it down 

 and burning it." 



"To save healthy trees within the affected districts in places where they are 

 surrounded by large numbers of dead or dying trees is difficult unless the above 

 measures are very thoroughly carried out. But the chances of their infection may 

 be very largely diminshed if they are brushed with Bordeaux mixture on the leaf 

 sheaths when the removal of diseased trees commences. Bordeaux mixture is a 

 substance which adheres strongly to the surfaces of plants, and being poisonous 

 to fungus spores it prevents their germination or kills the young germ filaments 

 as soon as they appear." 



"A second gang of toddy drawers should be employed for this work and 

 provided with small vessels containing the mixture and mops of rags for brushing 

 it on to the sheaths. The expanded leaves need not be brushed, but only the leaf 

 sheaths below these. One man should be able to do from 30 to 50 trees in a day, 

 and if the work is done at the time that the trees are climbed for cutting the leaves 

 the cost of the labour should be small. The men employed for removing diseased 



