196 TBTNIDAD AND TOBAGO BULLETIN. [XVIIL 4. 



Neither the roots of the trees ror the course of the disease follow 

 re^'ular lines, and it is quite improbable that all the eight contacts are 

 infected, but there is no practicable means of knowing whicli remain free. 

 In order to save those which are still uninfected, it is advisable to cut up 

 the enclosed area chessboard fashion as indicated by the dotted lines. 

 If these secondary trenches are omitted, it is likely that the contacts 

 will all go off sooner or later in the manner already described. 



In situations where there is a risk of soil infections the trees still 

 further out, (H...H in the diagrams), should have some special attention, 

 especially if D is in an advanced case when discovered. 



One lime planter in Dominica has anticipated events and has 

 separated his trees throughout by trenches in both directions, so that 

 each stands in a square plot cut off from the rest. This measure is 

 regarded by the owner, and by Mr. G. A. Jones, who has reported on it 

 from time to time, as having completely changed the prospects of the 

 estate. Whereas the losses from root disease were becoming increasingly 

 serious and were quite out of control, they are now reduced to occasional 

 sporadic cases which cause no apprehension. 



While few planters will be disposed to go so far as this except 

 under pressure of heavy losses, there is much to be said for the general 

 adoption of the system represented in the second diagram (II), where a 

 permanent drain denoted (by a double line) exists between every row 

 and the next. All that is required for isolation is the cutting of cross 

 trenches between (J and H, to separate contacts from healthy trees, and 

 secondary cross trenches between D and C, to save the contacts if they 

 do not prove to have become infected. The length of isolation trench 

 required is reduced to one-sixth. It will be objected that the provision 

 of the drains in the first instance involves much more expense, but 

 apart from such purely agricultural benefits as may be obtained, the 

 difference is a very practical one between cutting trenches in a 

 systematic way, and at a convenient time, on the one hand, and on the 

 other hand having to do it as an emergency measure, it may be at a time 

 when it is highly inconvenient. It may be suggested that the expense 

 of draining should be discounted by regarding it as a system of insurance, 

 whereby from each sporadic case of disease which occurs, two trees only, 

 instead of eight, are exposed to root infection. The adoption of such a 

 system would prevent the development of the large open spaces, 

 extending sometimes over the sites of dozens of trees, which are the 

 most disquieting feature of clearings where this disease has become well 

 established. There are arguments for this type of draining as a purely 

 agricultural measure in wet districts, and there are instances in 

 Dominica of its adoption on such grounds alune. The most serious 

 objection I have heard urged against close draining in lime fields 

 concerns the inconvenience and loss experienced in the collection of the 

 crop, but I doubt if this comes near to balancing the advantages of the 

 system. On steep slopes, of course, the trenching will have to be 

 carried out with due regard to contours and the danger of slips and 

 of wash ; on all recent clearings there will be breaks due to large stumps. 

 There are some situations where the method is quite out of the question, 

 but the}' atibrd no argument against applying it where difficulties are 



