266 



THE AGKICULTUKAL NEWS. 



August 25, 1906. 



CACAO DISEASE IN TRINIDAD. 



The following is a preliminaty report by Mr. F. A. 

 Stockdale, B.A., Mycologist on the start' of the Imperial 

 Department of Agriculture, on a visit to a cacao estate 

 in Trinidad, on which disease was reported to be 

 prevalent : — 



Mr. Stocl'dale — to the Act in;/ Colonial Secretari/, Trinidad. 



Port-of-Spain, 



July 16, 1906. 



Sir, — Acting in accordance with instructions received 

 from his Excellency the Acting Governor, I attempted to 

 make arrangements for a visit to Mr. C. deVerteuil's estate 

 at Montserrat, in order to investigate a disease of cacao, 

 which was reported to be causing considerable damage. 

 Finding that such an arrangement could not be made, 

 I decided to visit ilr. V. dcBoissiere's estate, St. Marie, 

 where the disease was also reported as being prevalent. 

 I paid a visit to this estate on Saturda)-, Jul}- 1-t, 

 accompanied by Mr. V. deBoissiere and Mr. J. H. Hart, 

 F.L.S., and went through practically the whole of the 

 plantation, where I was able to e.xamine many trees in order 

 to gain a fairly accurate idea of the nature of the disease and 

 its economic importance. 



2. On entering the plantation, many of the trees were 

 noticed to have the tijis of the branches dying back. The 

 first sign of the disease appears to be the drooping of the 

 leaves, which soon afterwards drj- up and assume a somewhat 

 reddish appearance. The decay of the branch seems to 

 commence at the tip and graduallj- to work backwards. The 

 dead wood turns a brownish colciur and dries up. 



Microscopic examination in the regions of the brownish 

 discoloration revealed the presence of a mycelium of a fungus, 

 but careful search did not disclose any spores, and, therefore, 

 it is at present impossible to identify it. In .some twigs it 

 was akso noticed that a small insect had made an entrance 

 through the buds into the i)ith of the young stem. The 

 relation between the fungus and the insects has not yet been 

 demonstrated, nor could their direct bearing upon the disease 

 be determined during my short visit to this estate. 



.3. Extent of Darnaye. — In one corner of the plantation 

 this disease was troubling several trees, but, in most cases, it 

 appeared to be lindted to the ti{)S of the younger shoots, and 

 in very few in.stances were whole branches killed out. 



4. Suggested Remedies. — As this disease appears to com- 

 mence with the tips of the young shoots, and to work 

 downwards, all twigs that present this brownish drying-up 

 .should be removed at a point somewhat below the lowest 

 limit of the disease. These diseased portions should be 

 removed from the plantation and destroyed, preferably, by 

 fire. On no occasion should diseased branches be left lying 

 on the ground under healthy trees, as they often become 

 covered with spores, and are therefore a source of infection. 

 The stumps of the branches from where the diseased portions 

 have been removed should be tarred in order to prevent 

 further infection of the tree bj- means of fungus spores. 



CANKER DISEASE. 



5. On proceeding further into the plantation many large 

 branches were observed to be dead. (Jn examination these 

 showed that they were covered with fungus spores which had 

 pushed through cracks in the discoloured bark. The spores 

 are of several ditl'erent kinds, and vary in colour from whitish 

 yellow to deep red. These spores belong to a fungus of the 



genus Kectria, which is the organism that causes ' Canker.' 

 Undoubtedly most of the dead branches and stems had been 

 killed by this fungus, for its symiitoms, viz., exudation of 

 a gummy ]i(piid from the bark and claret-red discloration of 

 bark, were noticeable. From a superficial examination through- 

 out this part of the plantation, the branches appeared to be the 

 parts of the tree that were suffering most, but in many 

 instances the stems of the trees showed that they were also 

 attacked. 



REMEDIAL MEASURES. 



6. This fungus belongs to a group of fungi that are 

 wound-parasites ; remedial measures have frequently been 

 suggested and have proved beneficial. Numerous articles on 

 the methods used in combating this disease have frequently 

 appeared in the jjublications of the Imperial Department of 

 Agriculture for the West Indies and also in the Bulletin of 

 the Botanical I)e)iartment of Trinidad, and therefore I will 

 only briefly mention those which I consider the most impor- 

 tant : — 



(</) All dead trees killed by 'canker' should bo cut 

 down at the ground and destroyed, preferably by 

 burning. 



{h) All diseased branches should also be removed and 

 destroyed. The cut surface on the tree, after 

 removal of diseased branches, should be coated over 

 with a layer of tar, to i)revent rotting and further 

 infection. 



(c) All discoloured bark, and about an inch or so of the 

 surrounding apparently healthy bark, should be cut 

 out from all" attacked stems — the disea.sed bark 

 being collected and burnt, and the wound on the 

 tree tarred over. 



((7) When the trees are pruned, all the cut surfaces 

 should be covered over with a coating of tar. 

 It is also very important, in the pruning of 

 trees, that no cutlass or pruning hook that has been 

 used previously for cutting out diseased portions of 

 trees should be used for [iruning purposes, unless it 

 has been properly cleaned and sterilized ; otherwise 

 spores may be carried from a diseased tree to 

 a healthy one. 



((') The importance of pruning, preferably done in the 

 dry season, is obvious, for it allows the entrance of 

 more sunlight. This, in Ceylon, is considered 

 often to prevent the spores of the fungus from ger- 

 minating, and aids the tissues of stem.s, etc. in 

 their efforts to heal wounds. 



(f) The burial of all husks is also desirable, for several 

 instances were noticed of the fungus living on the old 

 husks that had been heaped up. The heaping of 

 husks, therefore, causes another source of infection. 



7. The jilantation of younger cacao was also examined, 

 but very little disease was noticed, most of the trees beinc in 

 a healthy condition. 



^. In conclusion, I feel sure that the above remedies if 

 adopted, will keep the disease well in hand, and that the 

 sj-stematic removal of all diseased branches, etc., and tarring 

 of all wounds should overcome the disease eventuall}-. This 

 would possibly become the more marked with drier weather. 

 I have, etc.. 



(Sgd.) F. A. 



STOCKDALE, 



Mycologist. 



