March, 1910,] 



225 



Plant Sanitation. 



MISCELLANEA: CHIEFLY PATHO- 

 LOGICAL. 



By T. Petch, B.A., B.SC- 



The fact that our common root 

 diseases in new clearings usually spread 

 from jungle stumps is now generally 

 admitted, and the possible danger at- 

 tending the tropical method of opening 

 estate is beginning to be recognised. 

 But any alteration in this method is 

 rendered impossible, first by the cost of 

 removing stumps, and secondly by the 

 need of planting as soon as possible in 

 order to shorten the compratively long 

 period which must elapse before the 

 estate becomes remunerative. Further, 

 in temperate climates, where machinery 

 is employed, the land must be complete- 

 ly cleared before it can be worked, but 

 in Ceylon, at least, under present condi- 

 tions, where level land is not available, 

 this necessity cannot exist. 



It has been recently proposed that, in 

 order to avoid the danger of root 

 disease, estates should be planted, when 

 first opened, not with the product which 

 it is intended to cultivate permanently, 

 but with some other plant which can be 

 grown for three or four years with a 

 reasonable prospect of profit and then 

 cut out. In this way, the jungle stumps 

 would be given .time to decay, and any 

 root diseases which might arise would 

 attack only the temporary crop. These 

 diseases could then be dealt with as 

 drastically as wished, without any 

 hesitation on the ground of permanent 

 loss. The land would then be clear of 

 disease and be planted up permanently. 



Though this method would certainly 

 diminish the risk of root disease, it is 

 rather too much to assume that all root 

 fungi would be got rid of. Some of 

 them can live independently in the soil, 

 while others require no more than dead 

 leaves, or a few chips, to enable them 

 to begin their growth. Apart from this, 

 however, the method will scarcely re- 

 commend itself to the rubber planter 

 of the preseut day who wishes to see 

 some return for his money as soon as 

 pissible, and lu will without doubt 

 continue to take the risk of root disease 

 rather than add four or six years to 

 his enforced waiting period. And it 

 must be admitted that the comparative- 

 ly small losses from root disease in 

 Ceylon justify his attitude. 



But the proposal immediately suggests 

 the question, how long does it take jungle 

 stumps to decay ; and to this question 

 no answer can be given, though it would 

 be thought that sufficient data would 

 surely be available in a country where 



so much jungle has been felled and 

 cleared. No one, however, has been suffi- 

 ciently interested to take notes, and 

 therefore information on the subject is 

 necessarily vague. The question itself 

 is of course somewhat vague, since the 

 time of decay must depend on the kind 

 of stump, the elevation of the district, 

 and to a great extent on the weather. 

 And if the stumps are attacked by 

 white ants, their duration is consider- 

 ably briefer than would be the case 

 under other conditions. Yet granting 

 all that, it should be possible to fix 

 approximately the time which a planter- 

 would have to wait if he adopted the 

 scheme outlined above. 



Probably few psople outside the small 

 band of fungus collectors have any idea 

 of the length of time for which stumps 

 persist. Certainly few others have any 

 incentive to make observations on the 

 subject. A dead stump is a garden of 

 fungi, and hence a mycologist, if he 

 takes any interest in the subject outside 

 his laboratory, devotes special atten- 

 tion to them. When he collects in a 

 limited area he comes to know the ex- 

 act location of each stump, knows what 

 fungi grow regularly on each, and in 

 many cases hands on his knowledge to 

 the next generation. In temperate 

 climates, at least, he would be very 

 much surprised if on making his usual 

 rounds he found that some of his pet 

 stumps had disappeared otherwise than 

 by the hand of man. 



It would appear that, given the maxi- 

 mum amount of assistance by white 

 ants, the stumps of soft-wood trees, 

 may decay fairly completely in about 

 four years in a wet low country dis- 

 trict. On a rubber clearing in the 

 Kelani Valley most of the stumps had 

 been attacked by white ants and were 

 in an advanced state of decay in the 

 fourth year. 



In the Matale district, the stump of 

 a 10-year-old Hevea tree was barely 

 recognisable at the end of four years ; 

 this tree had however been killed by 

 root disease, and consequently the main 

 root would be partly decayed before 

 the tree died ; as it was subsequently 

 attacked by white ants, the conditions 

 were extremely favourable for rapid 

 decay in this case, Hevea must be 

 classed with the soft-wood trees, and 

 it is probable that at least six years 

 would be required for the decay of 

 such a stump, if originally sound, in 

 that district. The stumps of two trees 

 which were felled at Peradeniya in 1903 

 have provided successive crops of fungi 

 for the last seven years ; they have 

 been attacked by white ants to some 



