272 
THE TROPICAL AGRICULTURIST 
[Oct. 1 , 1897 . 
Department by informing the Director of important 
occurrences, such as the opening of new cultivations, 
the abandonment of old ones, outbreaks of disease, 
results of trials and experiments made, and so on. 
All information thus obtained will, if desired, be treated 
as. conftdential. 
In publishing these papers of instructions, sugges- 
tions, criticisms, &c., we do not intend to speak dog- 
matically, nor is it our desire that our instructions 
should be blindly followed. Our aim is rather to offer 
suggestions or criticisms which the individual cultivator 
may apply as he thinks best to his own case. In purely 
horticultural work, it is indeed possible that the most 
skilful men employed in these Gardens may be the 
equals or even superiors of any in the Island, but in 
the larger agricultural enterprises this cannot well be 
so. The practical knowledge of a skilled planter of 
tea, rice, or other such produce ought to be much 
greater than that which we possess in the same 
line. On the other hand, their scientific knowledge 
and acquaintance with cultivations of all kinds of 
plants in the Botanic Gardens and in different parts 
of Ceylon and elsewhere places the members of this 
staff in a good position to criticize methods in use, 
to suggest new or better ones, to try experiments in 
all directions with the best chance of obtaining good 
and reliable results, to advise in cases of doubt, 
difficulty, or disease, and so on. Thus, in the in- 
troduction of new cultivations into Ceylon — c.</., of 
cinchona in the past and of Para rubber in the 
present — this Department may prove of signal service, 
not only by providing plants, but by instruction in 
their cultivation and preparation for market. But when 
once the cultivation is fully established its function be- 
comes more confined to advice and criticism, the study of 
diseases, &c. Expenditure on this Department (which 
at most amounts to about one-fortieth per cent, of the 
value of the produce annually grown in the Colony) 
should be regarded by cultivators rather as an in- 
surance than as a directly remunerative invest- 
ment. The successful introduction of such cultiva- 
tions as cinchona, Liberian, coffee, cacao, rubber, and 
many others is alone sufficient to have amply re- 
paid all the cost of the gardens. The experimental 
cultivations and other scientific work carried on in 
the gardens cannot by their very nature be 
directly remunerative, but may indirectly repay their 
cost many times by establishing new industries, 
by saving old ones from losses by disease or otherwise, 
by introducing improved methods, and so on. 
The next Circular issued will probably deal with the 
disease now attacking cacao, and others to follow 
shortly will treat of the cultivation of Para rubber in 
Ceylon, of the chocho as a useful vegetable, of new 
ornamental plants, and many other questions. 
John C. Willis, Director, Eoyal Botanic Gardens. 
THE CACAO CANKER. 
EXTEACTS (with additions) FEOM HEPORT OF THE 
DIRECTOR OF THE EOYAL BOTANIC GARDENS AND THE 
honorary GOVERNMENT ENTOMOLOGIST. 
Official and public attention was first called to this 
disease in February, 1897, by planters in the Matale 
District. 
2. We have visited numerous estates in the districts 
of Matale East and West, Kurunegala, Hunasgiriya, 
Wattegama, Alagalla, Hantane, Badulla, and Veyan- 
goda, and have found the disease in nearly all of these 
districts, but especially in Matale. 
3. The date of the original appearance of the 
disease is uncertain, but most cacao planters are 
agreed that it has been prevalent since 1892 or 1893, 
increasing in extent every year. Certain experienced 
planters state that they have observed the disease 
upon cacao for the last twenty years. The area now 
affected is a very large one, and the disease is causing 
death or serious loss of crop in many thousands of trees. 
4 . The disease is practically confined to the variety 
known as the “ old red ” cacao of Ceylon (GrioUo), 
the hardier Forastero variety being usually unaffected, 
Many estates are steadily replacing the former by 
the latter. 
5. The disease appears to spread to new trees only 
or chiefly during the wet weather of the north-eas* 
monsoon, and we have therefore not been able t° 
find any of the very early stages of its action or t<^ 
determine its exact nature. 
6 . The recognition of the disease by external ex- 
amination is often difficult. In the earliest stage 
which we have been able to find there is usually a 
darkening of the surface of the bark. This appearance 
however does not necessarily indicate the presence of 
the disease : darkening of the bark is often a result 
of other causes. When the disease is more pronounced 
a pinkish gummy matter exudes from the diseased 
surface. This is known among cacao planters as 
the “ bleeding” stage, and is often considered as 
indicating the first appearance of the disease, whereas 
at this period it is in reality well established. On 
shaving away the surface irregular discoloured 
patches are observed. The tissues of these, instead 
of being of the normal whitish or yellowish appear- 
ance, are usually of a claret or brownish red colour. 
The diseased patches are usually surrounded by a 
definite cork-cambium layer, visible as a narrow 
dark line. The diseased parts may remain living 
for a long time, but ultimately become dead and 
shrivelled. The disease appears to begin at the 
surface and Work inwards. Sometimes in vigorous trees 
it is found that the diseased parts are being thrown off 
by new growth from below. Most commonly, however, 
the disease has worked inwards to the cambium 
layer (at the outer limit of the wood), which is found 
dead and decayed and of a brownish colour. This 
discolouration was often found to extend upwards in 
the tissues of the newly-formed wood into otherwise 
healthy parts of the stem. Even at this stage growth 
from below may cut off the diseased part. In some 
cases of vigorously groiviug trees it has been 
found that if the diseased parts be completely 
cut out the tree may recover unless infected in 
new places. The branches of diseased trees die 
off from above, but are not themselves affected 
by the canker. When a diseased patch is im- 
mediately below any branch that branch usually 
dies. Frequently the disease spreads completely round 
the stem, and the whole tree dies above that point, 
but may be replaced by the growth of suckers below it. 
The roots and young branches are apparently un- 
affected by the disease, which seems to be confined 
to the bark of the older and mature stems. 
7. In the diseased parts of the bark are fre- 
quently found the small tunnels of a boring beetle 
{Tomicus sp.). The farther advanced the stage of 
the disease, the larger the number of these tunnels. 
The presence of these tunnels and of the insects that 
form them has led to a very general opinion amongst 
cacao planters that the disease has been caused by 
these insects. Extended examination has however 
shown that the insects are a consequence, not the 
cause, of the disease. In a large number of cases the 
disease is found to be well established without any 
indication of insect attack. In such cases small irre- 
gular canals in the substance of the bark, caused by 
the death and breaking up of some of the cells, are 
often mistaken for the work of boring insects. But 
these irregular openings are very distinct from the 
cylindrical tunnels formed by the Tomicus. 
8 . It seems therefore probable that the disease 
is of a fungus nature, but no definite fungus 
has as yet been found in the diseased parts. 
It has been stated above that the disease 
spreads at a particular time of the year, and the 
fungus if present is now (July) probably in a resting 
condition. 
9 Like most other diseases, this one appears to 
especially attack debilitated trees. Care should 
therefore be taken to keep the trees in as healthy a 
condition as possible. Among the causes which may 
weaken the tree (and which we have observed in 
operation on many diseased estates) are unsuitable 
soil, want of manure or injudicious manuring, too 
sudden or violent reduction of shade, bad drainage, 
the attacks of boring and other insects, inattention 
to selection of seed, and careless mutilation of trees 
in removing suckers or cutting out boring insects. 
