176 TRINIDAD AND TOBAGO BULLETIN. [XIX. 4. 



The failure of the tree is marked by a progressive yellowing and 

 browning of the leaves in order of age, commencing at the tip of each 

 leaf reached in the process. In its early stages the discoloration is 

 indistinguishable from that which accompanies the natural dying off of 

 the old leaves, especially where this is accelerated from any cause. The 

 difference becomes apparent however when leaves in full vigour and 

 even those not fully expanded are involved. The shedding of green nuts 

 is one of the first symptoms of this disease, as also of bud-i'ot. 



"When the stem of an affected tree is cut across a well-marked red 

 ring 1 to 1^ inches wide beginning one to two inches from the outside is 

 found. It is densest near the base of the tree and broken into more or 

 less scattered dots as the leaves are approached. The leaf bases when 

 split open show a somewhat similar discoloration. Infested I'oots have 

 the loose cortical tissue discoloured yellow, pink or red 



The evidence so far obtained goes to show that infection begins in the 

 crown and extends downward and it is assumed that the worms from 

 infested soil travel upwards on the outside of the stem when it is in a 

 moist condition, and enter about the bases of the leaves. Infection can 

 be artificially produced with great readiness by dropping a fragment of 

 infested tissue into the axil of a leaf, and the infestation so produced is 

 identical with that found in naturally infected trees. 



It is rare for trees to show signs of infection at less than four to five 

 years of age. In the great majority of cases the trees develop the disease 

 during the bearing of the first few crops of nuts. After this stage the 

 trees begin to grow out of their susceptibility to infection and where 

 development is normal cases are rare in trees beyond the age of ten 

 years. No influence on liability to the disease appeai-s to arise from any 

 variation in soil or other external conditions. 



The earliest cases which occur in a field are few and scattered and 

 may be supposed to arise from infected nuts, though there is as yet no 

 proof of this. Later cases are mostly grouped around those first to 

 appear and are obviously due to infection from them. The losses from 

 a severe infestation may amount to .';0 per cent, before the period of 

 immunity is reached. 



The cure of the disease is regarded as impossible. The measures 

 which have been suggested for its prevention are at present in process 

 of trial on an extensive scale. An obvious precaution is to destroy the 

 infested trees immediately upon their condition becoming recognisable. 

 They should not be cut down but should be dug out, which is almost as 

 readily done, and then burnt or at least thoroughly charred as soon as 

 sufficient dry fuel is available for the purpose. It is worth considerable 

 expenditure to tackle the early cases in this way in view of the disastrous 

 effects which often follow their neglect. Observation shows that it 

 should also be worth while to isolate threatened trees by cross trenches 

 connecting the drains which usually run between the rows. A further 

 measure which is undergoing tests is the painting of a band of crude oil 

 about a foot wide round the stem with the object of stopping the ascent 

 of the worms by providing a surface upon which moisture will not lodge. 



