52 



annosus, attacks at first the lateral roots and works its way into the 

 stem, where it sets up a destructive rot, eventually killing the tree. 

 Similarly the Rosellinias, of which several different species are 

 responsible for the disease known as " stump rot," which is so 

 common in tea and coffee estates, act in much the same manner. 

 In all, from the position of the attack, remedial measures are 

 extremely difficult, though the fungus may be prevented if taken 

 in time from spreading to adjoining trees. The case which has 

 been most fully tested is " stump rot." Several outbreaks of this 

 have been checked on the writer's recommendation by trenches 

 carried round the diseased patch in the earlier stages. The trenches 

 were about two feet deep and a foot broad and were carried well 

 outside the ground which the diseased roots might be expected to 

 occupy. The trees inside the trench were pulled up and burnt, 

 the ground being levelled and allowed to remain fallow for over 

 a year. No new cases occurred outside the trench, though where 

 this treatment is not adopted the diseased patch continues to 

 expand almost indefinitely. Similar results have been obtained in 

 Ceylon and elsewhere. 



The following observation suggests that the same treatment may 

 be successful in checking the betel-palm root disease. In a village 

 near Kanairghat, I visited a very large garden in which over fifty 

 per cent, of the palms were dead or dying. One corner of this 

 was found almost entirely free from the disease. This was separated 

 from the rest by a ditch which cut off sharply the diseased from 

 the healthy portion. Everything appeared to indicate that the 

 salvation of this part of the garden was due to the presence of the 

 ditch. 



To be effective, trenching must be undertaken as soon as the 

 first disease appears in a garden. The trench should be two feet 

 deep, about a foot broad and drained so as to prevent water 

 accumulating in it. It should entirely surround and cut off the 

 first affected palms. It is unusual for the whole of a garden to be 

 attacked simultaneously. Generally, one or a few trees, are first 

 affected, the disease spreading from these. Though it is probable 

 that a part of the spreading is due to spores, infected soil or 

 something of the sort being conveyed through the air or on the 

 feet of the cultivators, the main infection occurs through the 

 ground. Very few known fungi travel through the subsoil, most 

 living in the upper layers and, where parasitic, attacking the 

 superficial roots only. Hence a gap in the soil two feet deep is 

 amply sufficient to stop this progress. But while the mycelium 

 cannot gain access through the air, it probably can through stagnant 

 water and certainly through dead leaves or debris, should any be 

 allowed to lie in the trench. Hence it is absolutely necessary to 

 keep the latter clean aud to drain off any standing water which 

 may lodge in it. Should it be desired to utilise the ground inside 

 the trench for replanting at an early period, the diseased palms 

 should be cut clown and their roots dug out and the ground turned 

 over at frequent intervals for a year. This by itself is frequently 

 sufficient to destroy the last traces of a parasitic fungus in the soil, 



