April, 1910.] 



331 



Plant Sanitation, 



Nature of Soils as affecting the 

 abundance of t. gestroi. 



In view of the fact that the termitaria 

 are contained invariably if not exclu- 

 sively in timber, it may be concluded 

 that soils only indirectly affect theabund- 

 ance of T. Gestroi, i.e-, certain soil? are 

 favourable to the growth of trees 

 affected by T. Gestroi. 



The soils may affect the extent of the 

 attack on rubber trees by being more 

 or less easy of penetration when the 

 termites go abroad in search of food. 



Methods of Extermination. 

 On Old Rubber Trees. — It has to bedeter- 

 mined whether T, Gestroi establish their 

 termitaria in the rubber trees themselves, 

 and on this point I have no data. If it 

 should prove to be the case, fortunate is 

 he who discovers an insecticide, or other 

 means, by which the Queen cells may be 

 reached, at a low cost and without 

 destroying the tree, and thereby obtain 

 the reward now being offered. On the 

 other hand, our success in exterminating 

 the pest depends upon the skill with 

 which the runs are traced up to their 

 base. If all timber is collected and 

 destroyed I feel convinced that if the 

 attack does not entirely cease it will be 

 very much diminished. 



On Young Rubber Estates.— I have 

 found it cheapest and best to make a 

 systematic search field by field and line 

 by line for all timber which is known to 

 be favoured by T. Gestroi, cut them 

 open with an axe or cross-cut saw, and if 

 they contain the slightest trace of the 

 enemy destroy them by burning. 



The danger of scorching the surround- 

 ing plants may be entirely done away 

 with, or at least greatly minimized by 

 burning in a trench, keeping the fire 

 covered with green stuff, and shielding 

 the surrounding trees with sheets of 

 corrugated iron. 



These should not lean against the 

 rubber trees but be supported by sticks 

 a short distance from them ; even if two 

 or three rubber trees are destroyed by 

 fire in this way, the damage done is 

 more than compensated for, by the fact 

 that one T. Gestroi termitarium is cap- 

 able of destroying a score or more of 

 trees to a distance of two or three 

 hundred feet. 



Where there is a sale for timber or 

 charcoal, sound Meranti trees may be 

 sawn up with advantage and Kuiupas 

 can be converted into first-class charcoal. 



A close watch should always be kept 

 on land that has been cleared of timber, 

 and if a tree is seen to be attacked, every 

 endeavour should be made to discover 



the source of infection, which will in" 

 variably be found to be a buried root or 

 stump, from which the termites make 

 their way in search of food by means of 

 tunnels. These may be found at a depth 

 of (/' to 3' below the surface of the 

 ground. In flat land I have never found 

 them below the subsoil water level, 

 which, of course, is regulated by the 

 efficiency of the drainage system. 



These tunnels are, as a rule (as Mr, 

 Pratt says) sufficiently large to admit 

 the introduction of an ordinary micros- 

 cope slide, though sometimes smaller, 

 they are perfectly smooth and are lined 

 with a red substance, probably the 

 excreta of the termites which takes its 

 colour from the timber on which they 

 have been feeding. This colouring 

 greatly facilitates the following up of 

 the tunnels, but it is by no means an 

 easy matter until the coolies become 

 practised at it, and see for themselves 

 that they are doing real good and not 

 merely following out some mad scheme 

 of their masters. When the direction of 

 a tunnel is lost it is very difficult to 

 pick it up again. I have found the 

 surest means of not losing it, is to 

 use a piece of thin flexible wire or 

 strip of cane as a probe. Pass it into 

 the tunnel as far as it will go, remove 

 the top soil carefully with a chunkol, 

 then break open the run to the end of 

 the probe. Pass the probe in again and 

 proceed as before until the termitarium 

 is reached. To find the tunnel or to pick 

 it up again should it be lost, I have 

 found it a good plan to cut a trench 

 round the tree attacked or the spot 

 where the run was lost. This trench 

 should be to the depth of the water 

 level, say two feet, and should be 

 examined the next day when it will 

 often be found that the termites have 

 made their way across by means of a 

 mud casing, thus determining the direc- 

 tion of attack. 



It is a tedious matter at the best to 

 follow up these tunnels, and it is on this 

 account that I have found it expedient 

 to examine all timber which I know to 

 be likely to contain termitaria before 

 resorting to this means, thereby saving 

 much time and expense. 



At first I gave rewards for the Queens, 

 and have collected in this way upwards 

 of seventy undoubted specimens, but I 

 find that by this method the coolies 

 waste much of their time in breaking 

 up every smaller piece of the termitaria 

 in order to find the Queen cells. 



When a log or root containing the 

 termitarium has been discovered aod 

 destroyed, and the ground around it dug 

 up, it may safely be concluded Uiat the 



