Dec. 1900.] 



489 



PLANT SANITATION. 



Diseases of the Coconut Palm. 



By T. Petch. 



It is more or less axiomatic that the number of diseases to -which a given 

 plant is subject, and the virulence of such diseases if no special precautionary 

 measures are taken, increase with the spread of its cultivation. It is rather 

 surprising therefore to find from manuals and essays on coconut planting that 

 there is apparently no disease of the coconut palm worthy of mention. This 

 relative immunity is not confined to Ceylon, but, to judge from their publications, 

 is shared by all other coconut growing countries. Insect pests are well known, 

 and their treatment occupies a large part of the literature of the subject. Can it 

 be that every disease has been attributed to " beetle," or is it that the climate 

 of the coconut districts and the methods of planting really discourage the attacks 

 of fungi? I think it may be assumed that the latter to a great extent are inimical 

 to fungi in general. There have been alarming reports of coconut diseases in the 

 past, e.g., of leaf disease in Ceylon in 1889 ; but no very serious damage has been 

 done, and the disease— or the fear of it— has passed away, and left no trace, not 

 even a scientific record, nor a specimen by which it could be identified if it 

 occurred again ! 



During the visitation referred to, it was generally stated that the particular 

 disease was one which had been prevalent, but not serious, for a long time. With- 

 out a knowledge of fungi and a microscope such a statement in the case of a leaf 

 disease could be only a mere guess. But I have now to record a disease, apparently 

 of fungus origin, which really has existed for a longtime, but which has only 

 recently caused any serious injury or loss of trees. 



This was first brought to the notice of the Department in 1903, but no 

 information was left on record. Last year, a correspondent of the Ceylon 

 Observer called attention to the condition of some of the palms near the Negombo 

 Canal, and stated that "dead and dying palms were seen from the boat, between 

 the second and fourth milestone on the canal. Sap was exuding from what 

 appeared to be punctures on the stem made by an insect." In the early part of 

 this year information to the same effect reached Peradeniya from several sources, 

 and this particular locality was visited. 



The affected trees are on a small island bounded by the canal and ditches, about 

 a foot above the water level in the dry weather. The surrounding marsh is planted 

 up in coconuts ; these are remarkably stunted, so much so, that they resemble 

 cycads. The diseased trees were covered to a height of seven or eight feet with 

 black patches, caused by the exudation of sap from minute cracks in the outer 

 tissue. The upper portion of the stem was usually unaffected. The tissue imme- 

 diately beneath the crack becomes discoloured, generally brown at first and finally 

 black, and this condition spreads internally until the patches from adjacent cracks 

 coalesce. The whole of the interior of the trunk is ultimately reduced to a mass 

 of humus mixed with fragments of the harder fibres. In advanced stages the tree 

 bears only a few small fronds, but the '• cabbage " is not diseased. The bud remains 

 sound so long as a section of the stem shows a region of undecayed tissue. Severa 

 trees were dug up, and it was found that in general the roots were dead on the 

 side affected ; and as the material, both root and stem, brought away for micros- 

 copic examination did not show any fungus hyphse, it was thought possible that 

 the death of the trees was primarily due to the decay of the roots owing to the 



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