588 



The Supplement to the Tropical Agriculturist 



respective managers had not suspected the pre- 

 sence on their young plants of anything ini- 

 mical. They were all quite healthy in appear- 

 ance, but would have succumbed when planted 

 out, and each diseased plant would have served 

 as a centre of contamination from which healthy 

 plants would have been infected. 



Identification or Fungus. 

 Fructifications (fruits), such as the usual 

 " bracket mushrooms : ' found in abundance on 

 the dead logs and stumps of a clearing, have not 

 been noticed in association with this disease, 

 nor has it produced spores (seeds) notwithstand- 

 ing numerous infection experiments and long 

 continued cultures in various nutrient media 

 in the laboratory; consequently it is impos- 

 sible to give it a scientific nam9, an 

 omission which from the ' planters point 

 of view is not of much moment. It is 

 possible that a " bracket " fructification is 

 formed, and it may be discovered when the life 

 history of the parasite is more fully investigated. 

 The planter will then know the cause of the ill 

 health or death of a tree when he notices the 

 "brackets "on adjoining dead wood. On the 

 other hand the fruits may be so small as to be 

 invisible to the naked eye; and they may be 

 found on the living plant only or on dead wood 

 only. 



This parasite appears to belong to the dan- 

 gerous class of facultative parasites ; that is it 

 can live on dead wood (saprophyte), and if need 

 be on living wood (parasite). 



Fomcs semitostus, a "bracket'' fungus, has 

 been reported as a source of root disease here 

 and in Ceylon. I have found it on only two 

 occasions, and have not been ablo to connect it 

 with the disease under discussion. 



Kemedial Measures. 

 Though cure is almost impossible prevention 

 of further infection is fairly easy. Owing to the 

 absence of seeds (spores) infection must take 

 place underground, and only when a para root 

 is in contact with a jungle stump or log support- 

 ing the parasite. The under-ground strands of 

 threads of many fungi, such as Ayaricus mcllem, 

 a dangerous parasite on oak trees in forests of 

 the temperate zone, travel for considerable 

 distances through the soil, but seldom at as 

 great a depth as two feet. The present fun- 

 gus appears to have such a capacity in only a 

 limited degree. I have never found strands 

 more than a foot from a piece of root or decay- 

 ing log ; but the soil of a rubber clearing, es- 

 pecially when it is peaty, is full of roots and all 

 kinds and sizes of decaying wood. The spread 

 of the disease is likely to be much slower than 

 with those which attack leaves or other above- 

 ground parts, where wind, animals and human 

 agencies assist the dissemination of spores. On 

 the other hand living in the soil secures it from 

 the destructive influences of sunshine aud, in our 

 climate, of drought. 



In many cases where close planting has been 

 followed, managers pay no attention to trei-s 

 dying here and there over the estate, looking 

 on it rather as a premature removal of what 

 may have to be cut out later on. Such in- 

 difference is not wise, and may have costly 

 results. Except when stagnant water is the 

 source of tronblo, the death of a young tree is, 



according to my experience, generally due to 

 root disease, which can be easily identified 

 by the planter who is on the look out for 

 it. If preventive measures are not taken the 

 disease spreads and ad jacent trees begin to die 

 off. It is impossible to be too insistent upon 

 the importance of treating every diseased tree 

 as a possible centre from which many more 

 trees may be infected. 



As already mentioned the planter s efforts 

 must be directed to prevention. The diseased 

 area must be isolated, and precautions taken 

 against the possibility of the disease spreading. 



Attempts to cure are hardly practical, if in- 

 deed cure is even possible. An application of 

 lime to a tree but slightly attacked may some- 

 times be successful. Lime is alkaline and an 

 alkaline medium of this kind is not encourag- 

 ing to the growth of fungi. It is advisable and 

 beneficial to fork in unslaked lime round the 

 trees adjaoenttoone already killed by the fungus. 



The planter must aim at 



1. Starving the fungus by isolation and re- 

 moving all wood on which it may live. 



-. Killing it by exposure to the sun and by 

 applying lime. 



The diagram on this page indicates the 

 methods to be followed, aud which have been 

 carried out with success by several planters. The 



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black lines represent trenches : the dots trees ; 

 the one within the inner circle representing the 

 tree on which the disease has been discovered, 

 the others are to all appearances healthy. If 

 several adjacent trees are dead or known to be 

 diseased then the 



INNER TRENCH MUST BE MADE TO ENCLOSE THEM. 



The trenches should be lA foot deep and 9 to 

 12 inches wide. The earth taken out should be 

 thrown to the inside of the trenches. The area 

 enclosed by the inner trench should be turned 

 over to a depth of two feet on three or four 

 occasions at intervals of a fortnight, and roots, 

 branches and wood of all kinds collected and 

 burned along with the dead tree. There are 

 usually large logs which cannot be burned with- 

 out endangering neighbouring sound trees. 

 Such logs should at least be scorched and then 



