ROOT DISEASES 137 



the rest by main drains, and, where possible, each row, or two 

 rows if the planting is close, separated from the next by a trench. 

 There will be many patches encumbered with logs and stumps 

 over which for some years the system will extend only in the 

 plan, but it is necessary to take long view s, and too many cases 

 have been seen where, when the need for a trench has urgently 

 arisen, the line has been brought up against trees irregularly 

 planted and now too valuable to be destroyed. Drains are 

 being considered here, of course, not in view of their primary 

 function of removing water, but as isolation trenches preventing 

 the spread of root disease from tree to tree. At the same time, 

 thorough drainage may be considered to have direct value from 

 the point of view of Rosellinia disease, for although, as has been 

 pointed out, the fungus does not thrive in water-logged soil, 

 neither do the trees, and, when that condition has been passed, 

 the drier the soil can become the quicker is the decay of organic 

 matter and the less favourable the conditions afforded to the 

 fungus. 



It has been not uncommon in both lime and cacao fields, 

 when a large stump has appeared to be a centre of disease, for a 

 trench to be dug around it, cutting off the widely extending 

 roots. The best plan would probably be to dig a trench some 

 two feet wide well away from the stump, remove all sections of 

 roots, and fill it in again. 



In planting the trees, positions in close proximity to stumps 

 should as far as possible be avoided, and a good deal may be 

 done in the way of rearranging the smaller logs so that they do 

 not form too close a shelter about the stem of the prospective 

 tree. Beyond these measures little, for the time being, can be 

 done. 



When the first few years have passed and the logs are more 

 or less rotted, it has been shown to be quite feasible to hasten 

 very materially the time of their disappearance by cutting or 

 breaking them up so that they can be easily handled. Merely 

 to dispose of them better by dragging them away from the 

 stems of the trees is a considerable gain, and in some cases it 

 has been found possible to stack much of the material, and even 

 to make good use of it for fuel. The great convenience, quite 

 apart from root disease, of having the ground clear should be 

 an additional inducement to the planter to make every possible 

 effort to this end. 



A point to be always kept in mind is that wood which can dry 

 out from time to time, e.g., logs, stumps, or parts of them which 

 are raised above the soil and not shut in by weeds or overhanging 

 branches, is in little danger of harbouring the fungus. 



The same consideration applies to the soil. In damp, shel- 

 tered clearings, such as are favoured by the fungus, all that 

 is possible should be done to encourage the free circulation 

 of air beneath the trees. Low hanging branches which maintain 



