Nov. 1, 1898.] 
THE TROPICAL 
AGRICULTURIST. 
359 
CACAO DISEASE. 
MK. CARRUTHEKS' FINAL KEPORT. 
Kandy, 8tli October 1898. 
From Tlie Secretary Planters' Association of 
Ceylon. 
Sii!, — I enclose for i^ublicatioti Mr. J. B. Car- 
rntliers' Final Report on Cacao Disease and 
in continuation of lu3 interim Report published 
a few months a^o. — I am, Sir, yours faithfully, 
A, PHILII'. 
TO TIIE PLANTKRS' ASSOCIATIOX OF CEYLON. 
In preparing a report on the cacao canker it is 
difficult to select from the fa'-.ts observed those which 
teach more clearly the lessons which it is important 
for cuUivators to know and not, to burden the 
pamphlet with an amon t of detail which in some 
CAsea sheds only a small amount cf light on the 
Btibjec*. 
I shall endeavour to m?Jce thi-s account as popu- 
lar as is consistent with accuracy so that cultiva- 
tors having a practical and not scientific knowledge 
of cacao may not lose any information it may 
contain. 
When my investigations had been in progress for 
three months, I suhmitted an interim report, and 
in that descrihed the methods by which I en- 
deavoured to discover the nature and life history of 
the disease or dieases attacking cacao, so that in 
this report for the sake of brevity I need only 
give the facts arrived at. Any who are interested 
in the processes by which these facts were gained 
can hy reading the iuttrim report trace the method 
of investigation. 
Happily, the statements previously recorded need 
iu no case to be corrected and the further infor- 
mation gained as to the life-history of the canker 
fungus show.s that the deductions based on these facts 
were trustworthy. 
THE DISE.A.SE AND ITS EFFKCT. 
In the first place, I propose to describe the dis- 
ease as it appears to the planter and the effect pro- 
duced on the tree and its crop; nest giving the life ■ 
history of the fungus causing it — on the cacao— 
the means by which it spreads and the conditions 
favouring it and its increase, and thsn describe the 
treatment which after a series of varied experiments 
giive the best curative results — and seems to a great 
extent successful, as well as the preventive means 
which should ensure that all plantations at pre- 
sent not attacked by the disease may be kept free 
from it. 
It may be well to state here at once that in my 
opinion the result of the investigation has been to 
show that though no doubt the presence of the 
canker will mean an extra expense in cultivation 
(though not a serious one) it in no way threatens the 
protitablo cultivation of cacao and \vc may hope that it 
will lead to an improvement in methods and a conse- 
quent increase of yield. Of course an unknown enemy 
is always more alarming, but now that we have a know- 
ledge of the nature of the evil, it loses to a great extent 
its terror. The appearance of cacao both of the Foras- 
tero and CrioUo varieties is well-known to all cultiva- 
tors, and the numb.;r of deaths due to drought and tiie 
attac:U o£ inaoots and fungi was in Ceylon extr'.mely 
snniU until about live or six years ago wiien some plan- 
tera noticed a great increase in the number of casual 
deaths; and this increase wont on until it became a most 
serious ijiattor and scemeil to endanger the profitable 
cultiviiiion of cacao in Coylou. It wa.i not until the dis- 
ease had done damage to a very considerable extent that 
Etionlilic help was asked for and no doubt the loss 
might have been spared in great measure it investi- 
gations h,id Inion made soon after the disease ap- 
peared, and not delayed, until it had spread over such 
u large aroa. This, however, is nouly always tho 
history of such plant diseases and will ho so until 
the expcrionce has been dearly bought— that in plant 
lile just as iu human sanitation, sporadic diseases 
should be carefully observed and measures taken to 
prevent them becoming epidemic. It is a very self- 
evident fact, — but one that requires reiteration that the 
usual method of cultivation, viz., the unnatural crowd- 
ing together of one species — favours the rapid spread of 
diseases due to foreign organisms and therefore make 
prompt measures the more necessary. 
THE AMOUNT OF DAJIAOE. 
It is not very easy to estimate the amount of damage 
done as in many cases by siipplying nsv/ plants, tho 
estates have partially recovered, but there is no doubt 
that a serious monetary loss has bsen incurred, both 
by decrease of the crop and expense of supplying np 
diseased estates. I have visited some -10 estates in 
all districts of Ceylon, and though I am glad to say some 
places have for reason) afterwards mentioned not been 
attacked at all — yet in other cases, some estates have 
been practically wiped out by the canker. That the 
canker is confined to the stem and branches of the 
C3,cao, and does not affect the roots, is clearly shown 
by the following facts : — let when suckers are formed 
from the stumps of diseased trees cut down, they are 
quite healthy, and show no sign of disease, 2ndly, new 
cacao plants put in a few inches from the diseased 
trees grow vigorously and without disease, though tha 
roots of the two plants must be touching in many 
places ; and ordly, the examination of many roots of 
cankered trees showed no trace of the fungus, and 
all attempts to induce it in roots by inoculation 
failed. 
SIGNS OF THE DI:EA=sE. 
The first si<n of the disease apparent to the n iked 
eye is a darkening of a portion of the cortex of the 
tree caused by an excess of moisture immediately 
below it, and this is usually not accompanied by any 
'• shuck" appearance in tlie tree. In some cases the 
cortex has been pierced by insects at the moist places, 
and this causes an exudation at each puncture of a 
drop of claret-coloured fluid, which when it runs down 
tho cortex, and dries, gives the tree a rusty appearance 
over the dark spot. If the cortex be shaved off the 
tissue will be found to be soft and of a darkish claret 
or neutval colour, and so full of moisture that small 
drops exude from all over the cut surfac : which feels 
soapy and moist to the touch. This condition is due 
to the presence of the mycelium or roots of tho 
fungus in the bark tissues in latge quantity. Tha 
tree to replace the damage done to its tissues sends 
an abnormal amount of sap to tho diseased spot. 
The existence of such a moist area in the bark, means 
that the disease has been tor some time — .x varying 
time : in some cases, weeks ; in others months — in the 
tree, as it is now until the fungus has got a good hold 
of the tissues that anch an effect is produced. 
This characteristic discoloration of the bark tissues 
is variable ; in cases where the mycelium is only 
present in small quanity, the colour is very, little 
different from that of the healthy bark, and in many 
cases it is impossible for the eye to detect it. When 
the mycelium exists to any extent a neutral tint is 
produced, and this is gradually intausitied until when 
ihe fungus has completely permeated the b.irk cells, 
the discoloration is most marked. It this in'ected 
area is closely observed in the course of time — and as 
I will shortly point out this time varies con>iderably— 
a number of wdiitish pustules will be seen on the sur- 
face of the cortex (Fig i.) The pustules are of just about 
the size of a pin's head, and increase to the size sometimea 
of a large pea, and as a rule, they become pink later. 
These are the reproductive bodies of tho fungus, 
and consist of a mass of spores (spores may be for 
all practicable purposes, considered as the seeds of 
the fungus.) It is by means of these spores, that the 
canker spreads from tree to tree. If we examine tho 
tissues of tho b.rrk at a diseased spot microscopically, 
we shall find all the cells from the cortex to the old wood 
Dsrmoatcd by their strands (Fig. 2)— almost colourless. 
The mycelium of the fungus and these are more 
massed at the points whire they have forced their 
way through the cortex and produced their spore, 
pustules. The cortex of parts of a tree some eight 
or ten years old is as a rule slightly cracked iu 
places and it is at these weaker parts that tho spora 
masses are found protruding. As was muutiouecj 
