Fhb. 1, im.] THE TROrSCAL 
AaRICULTURIST. 
517 
CACAO CANKER IN CEYLON. 
(Continued Jrompage Hi.) 
Spoke Distbibution, 
The spreading of the spores over an estate is a 
most interesting, and the most impotant, question 
in relation to the canker, and has received a great 
deal of thought and attention from me, as it is by 
means of the spores that all the increase of the 
disease comes aboat. Though I have seen oases 
of iufection from pod to stem and vice versa by 
actual contact, these cases are so rare that we 
can neglect tnem and consider that the spores 
are responsible for all the extension of the disease. 
The methods of infection of different trees are 
very various, but we can distinctly point to three 
or four chief means of attack which have been 
constantly observed. In the first place, the wind 
has no doubt the largest share in spreading the 
spores, especially over large distances, and it is the 
wind which enables the disease to spread from 
estate to estate. Instances of this may be 
mentioned. In one case an estate was chiefly 
and first attacked at the point nearest to a native 
garden which had been entirely killed out by canker, 
and the trees allowed to remain after they were 
dead, a prevalent wind blowing from this direction. 
Cases similar to this are numerous. On the other 
hand, the disease is often absent from sheltered 
hollows, even though there were present all the 
conditions which favour it, because the wind passed 
right over and not through the cacao. 
The next and nearly as important an agent is 
water — both rain and river. Kain washing down 
the trees and dripping off the pods on to other 
pods or parts of branches and sterna carries with 
It the spores from infected places, and leaving 
them causes fresh spots. I have seen a tree covered 
with a mass of small fresh diseased places, all in- 
dependent of each other, below an old patch of 
cauker which was covered with spores. There have 
been many and clear proofs of rivers spreading the 
disease, in some cases, I fear, by the dead timber 
being thrown into the stream and conveying its 
deadly cargo to other places lower down ; and also 
a number of instances of cases of flood washing the 
spores over a flat area of cacao and infecting the 
trees. A very clear case of this was found in one 
young clearing, where practically every tree was 
cankered just above the surface of the ground, 
where a few inches of water had stood for a short 
time during a flood, 
But, in addition to both wind and water, ants and 
other small animals are the means of spreading 
the disease to an extent tl;at I think is hardly re- 
cognized. Any one who has watched the ceaseless 
activity of ants in running over stem, branch, and 
pods of cacao tree cannot fail to see how they 
must be the means of carrying from one place to 
another the spores when they pass over them. I 
have examined the legs and bodies of some ants 
which had been travelling over a tree having spores 
on Its bark, but without discovering these spores 
on them. But, considering the extremely small size 
of the spores, this does not materially weaken the 
contention, and, indeed, I should have been sur- 
prised if in any of the few cases I examined I 
had discovered any spores. The fact that the ants 
frequent the pods, where they feed on the secretion 
from the backs of the white Coccidcc that live on 
the juices of the pod, alone makes it probable that 
in the case of the pods the ants are responsible 
for a good deal of damage in carrying infection. 
How much part the pods take in spreading the 
canker in comparison to the stem and branches it 
in very hard to determine, but the rapidity with 
which the fungus grows in the pods, produces its 
Bpores, and spreads to other pods and to the bark 
leads to the supposition that in many cases the 
p>^9ntjr qI \h9 i^awEigQ is tlue t9 the ^i^e^»e it) 
the pods. It is unfortunate that in most estates 
the time when the largest nnmber of pods are on 
the trees is the wet season, which ia most favour- 
able to the fungus, and a suggestion may be offered 
in this connection. It is well known to cacao 
planters that the amount of fruit produced by each 
tree at the different crop times varies, that one 
tree produces a bigger spring crop uud not so big 
an autumn one as another; this is an individual 
characteristic, which is in many cases quite pro- 
nounced. If such characteristics are carefully selected 
in propagating (as has been done to produce the 
early and late varieties of cereals and many other 
cultivated plants), a plantation may be formed 
which will, in normal seasons, habitually produce 
its largest yield of fruit in the spring, when the 
dangers of sttaoks of fungi are much less, and when 
the planter has the advantages of sun in ripening 
his pods and curing his seeds. By continually 
using seed which has been produced in the spring, 
no doubt this would be graclu lly done; but it 
would be more effectually and quickly brought about if 
the planter would observe for a year or two those 
individual trees which bear their fruit more in the 
spring, and by using the seed from them get in 
time a spring crop variety. The attention of planters 
might also with reason be drawn to the practice of 
grafting, which Mr. Hart of Trinidad has' shown to 
be practicable in cacao, and which would, without 
doubt, lead to most interesting results. 
Tbeatment OF Cankered Trees; cl'tting 
OUT Cankbk. 
Before proceeding to discuss methods of preven- 
tiou and cure — which are in this paper the most 
important matters to be dealt with aud laid down 
—it is necessary to understand under what condi- 
tions fungi of the nature of this canker fungus grow 
and spread. 
The fungus grows in the stem, branches, and fruit 
of living cacao trees, and canuot grow for any length 
of time on dead portions or on the leaves or roots 
of the tree. 
For the growth of a spore of a fungus certain con- 
ditions are necessary : heat, moisture, and air. In 
Ceylon there ia always enough heat, at any rate in 
the cacao-growing areas: air is present, .but moistute 
enough is not always found. In dry weather there ia 
not enough moisture, unless under a heavy shade, 
for spores to grow, consequently they dry up aud in 
a majority of cases perish. In wet weather and 
under heavy shade spores alighting on cacao stem, 
branch, or pod will grow and produce an infected 
patch. The fungus growing in the bark takes some 
months before it produces its spores and can affect 
other trees on the pods; these are formed in two 
or three days. We therefore have to direct our 
efl'orts for prevention and cure to removing diseased 
tissue before the spores are produced on it, and 
to reducing aa far as possible the conditions under 
which the spores of fungi can germinate on the surface 
of the bark. 
In my last report published in the end of 18&8, 
nearly three years ago, certain rules were laid down 
for prevention and cure. These have been carefully 
and continuously carried out on one or two estates, 
partially on a good many others, very spasmodically 
and half-heartedly on others, and in a large number- 
in unfortunately the largest number— of cases, es- 
pecially those estates in native hands, no meana 
whatever have been adopted to stop the canker or 
prevent it producing spores to the danger of all othef 
cacao. 
If this Circular has no other effect than to in- 
duce cacao growers, as a whole, to take concerted 
measures against the spread of the disease, it will 
have fulfilled a useful purpose. Some three yeara 
have therefore passed— a sufficient time to juoge of 
the benefit of the measures adopted. 
The fiist rule laid down for treatment of the can. 
ber in stew and branch was "She whole of th^ 
