Nov. 1, 1898.] THE TEOPICAL AGRICULTURIST 361 
THE LIFF OF THE TEEB, 
In this connection reference may bo made to a 
belief which is current that the period of healthy 
life of the cacao tree is limited to about 15 years. 
A visit to some of the older plantations in Ceylon 
20 years and older, many o£ which are bearing now 
more per tree th»Q ever before would dispel this idea, 
and there seems to be nothing? to contradict the 
belief that if the cacao tree is properly treated, and has 
room to giOTT it should yield good crops for twice 
twenty years, and probably longer. In many cases 
where the borers, are allowed to ravage the tree 
without hindrance, the life of the tree is short, and 
in most cases where deaths are seen at so early an 
age as that mentioned above, it is due to this or 
other external causes. 
The most i nportant part of this report to the 
practical planter, however, is the portion dealing with 
preventive and curative measures. 
ritEVENTIVE MEASURES. 
The conditions necessary for the growth and spread 
of| fungi have been described above, and these con- 
ditions must, as far as possible, be kept away — but 
there are other enemies to consider in growing good 
cacao besides the canker Helopeltis, is in many cases 
tt very serious evil, and experience has shown that 
in many cases where the shade is taken away, the 
result is such an increase in the number of the 
Helopeltis that the cacao is seriously damaged. Wind 
is also very injurious to cacao in many places, and 
make it impossible to grow it without protecting 
shade trees. Much depends on the situation with both 
the enemies. There is cacao in Ceylon growing in the 
most excellent vigour (and this in one of the hottest 
districts) without a vestige of shade, and where the 
Helopeltis does not do much danger, there is no doubt 
that the cacao is much safer from danger of being 
attacked by canker when grown absolutely in the open. 
However,taking the Helopeltis as an enemy that must be 
reckoned with, it is important that the shade employed 
to keep away tliis pest should not be too dense to pre- 
vent the sun getting through, and keeping the air, and 
the stems of the trees dry. A liglit flickering shade is 
in most cases enough to keep away Helopeltis in great 
quantity, and such a shade at some distance above the 
cacao trees does not keep the undergrowth at all 
damp. For wind, of course, belts are the most effi- 
cacious, and not numerous trees growing among the 
caoac. 
In some cases the cacao trees are placed so near 
together (I have seen cacao 12 — 15 years old, six feet 
Bpartl with the branches overlapping each other that, 
although the overhea'1 shade may be light, the cacao 
itself is keeping the atmosphere around the stems 
damp and such conditions apart from the cramping 
effects on the trees are most favourable to the increase 
of the canker fungus. 
The preventive measures, therefore, are to keep 
the cacao under conditions which do not favour the 
germination of the spores. 
With regard to application of fungicides as preven- 
tive means. The best of these are those having 
sulphate of copper (blue stone) as their basis, 
Bordeaux mixture, &o. Sulphate of copper is the 
most powerful fungicide which has comparatively 
little effect on the external tissues of the plant, we 
know of. Experiments show that spores will not 
germinate in a solution of copper sulphate con- 
taining ojily one part in ."jOOiOOO. If a thin coating 
of this substance could be kept on stem and 
branch no doubt this would, effectually prevent the 
germination of any of the spores on the trees, 
but the time when the spores germinate is the time 
when there is continual rain, and during these periods 
it is practically impossible to keep the copper sul- 
phfito on the trees — every shower washing it away, 
riiongh I am a firm believer in the efficacy of copper 
sulphate as a preventive to fungi yet it seems to 
me that in the case of cacao cultivation it is not 
practicable. 
IIEMEDIAL IIEASUEES. 
Remedial measures are in plant pathology peculiarly 
Jjflftl to incbtribo autl Umc baa btcu uiftiol/ occU' 
pied since I have become acquainted with the natur^ 
of the disease with this most important question. 
In all cases of canker of bark whether fruit or 
timber trees the remedy has for many years been 
surgical, viz. : — To cut out the diseased tissue — and 
there is no doubt that in the case of the cacao 
canker this is the safest and most effectual remedy. 
I have tried several experiments with different sub- 
stances applying them externally in nearly all cases 
I had no expectation of success, but tried them 
owing to the belief in them held by practical men. 
In no case has there been any success and it ia 
more than improbable that there should be. The 
mycelium of the fungus permeates all the cells, the 
diseased tissue and any substance applied which 
would kill the mycelium of the fungus and must ne- 
cessarily kill the tissues as well and will most pro- 
bably damage a larger area of bark than is attacked 
by the fungus. The knife does exactly the same 
work and in a more efficient manner and even if a 
substance which could be trusted to destroy the 
parts affected were employed, it would be very much 
more expensive in Ceylon than the cost of labour. 
Tvro cases have come imder mv observation of estates 
where the canker appeared some two or three years 
ago and the plantations have been kept practically 
free from canker by this method of cutting out, 
and there is no doubt that, if this had been carried 
out genero,lly, that the loss by canker would have been 
out inconsiderable. 
"With regard to the application of " Tar" it ia in 
most cases absolutely harmful, as it acta as a water- 
proof over the diseased parts, keeps them damp and the 
growth of the fungus goes on beneath. It ia also a 
mistake as it conceals any bad work in cutting out 
when, for instance, no margin in left. 
The above treatment, viz., cutting out all the diseased 
tissue, and also a good margin of healthy 
tissue beyond, in order to take away the outlying 
strands of mycelium, which are not present in sufficient 
quantity to discolour the bark — has in no case I have 
seen failed, and I have seen many hundreds of trees 
so treated ; but there are unfortunately many estates 
in which the trees have been so long diseased, and such 
a large area of the bark invaded by the mycelium of 
the fungus that it is impossible without killing the tree 
to entirely remove all the disclosed tissue. In such 
cases other treatment must be resorted to ; but it should 
clearly be understood that complete excision is the only 
sure method of curing the tree. 
In cases where a large area on a tree is claret ot 
neutral coloured the treatment by shaving the cortex 
has been tried with varying success, in one estate 
it has been practiced for some three years with 
almost invari:'.bly successful results. 
A sharp pruning knife is the best instrument, 
though a spoke shave is very useful when the 
surface to be shaved is fairly even. All the 
discoloured part should be exposed, and, in ad« 
dition, a margin of one and a half to two inches 
should be also exposed round the discoloured 
part, leaving the claret or neutral portion in a frame 
of healthy bark. This is necessary as has been already 
explained because the mycelium spreads from the dis- 
coloured patch beyond and unless it is in a certain 
quantity gives no clue to its presence by any abnormal 
colour or moisture in the bark. All the shavings 
should be strictly collected and as they contain 
in nearly every case on the outside the spores of the 
fungus. 
When this shaving is properly done the exposure 
to the air (more especially with very thin shade) 
dries up the diseased tissue and in some eases the 
dry and dead tissue scales out and drops away; while 
the remainder of the bark being relieved from its 
enemy forms a healthy callus round the injury and 
in the course of time completely covers over the 
shaved part. This treatment has been tried on a 
good number of estates and only succeeds in ft pro- 
portion of cases. I should estimate about per 
ent. is certainly not loo high. The other 50 per 
cent, on examining the trees a week or ten days 
lulcr the mycelium tbcuyh grciitlj' >M;ftlieu«d in »« 
