THE TROPICAL AGRICULTURIST. 
[Dec, 1, 1900. 
the occurrence has been fixed by a 19th. century 
writer as "sometime during the last century." 
. The late Sir L. A. A. De Verteuil, k.c.m.g., m.d., 
in his book on Trinidad, page 431, states : — " The 
prosperity of the Colony had now reached its 
culminating point, Cacao selling at a high price. 
But in the year 1727 according to Guimilla, not a 
.disease exactly, but a blight attacking the pods 
under certain atmospheric influences, destroyed the 
crop." Later, he records that the Forastero variety 
was introduced and succeeded beyond expectation, 
and writes. " It is this quality which is cultivated 
in our days." 
In 1898 attention was specially called to a disease 
which attacked the pods of cacao destroying a large 
percentage of the crops in many districts in Trinidad; 
The matter was taken in hand by the Botanic 
Department and close investigation showed that the 
ods were destroyed by a parasitic fungus which could 
e speedily propagated by inoculation with spores taken 
from diseased fruit. Several cultures of the fanguB 
were made, and these, with other living materials, 
were sent to Kew for examination and report. 
The results of this examination were published 
" iii the '' Keio Bulletin" for January and February 
1899, as follows:— 
" Microscopic examination revealed the presence of 
two distinct fungus paratites; one being the well- 
known PJiytophthoi-a omnivo^a, De Bary, a species 
closely allied to Phijtophthora infestans, De Bary, 
the cause of the potato disease ; the other a Nectria, 
which proves to be new to science, and will be known 
as Nectria Dainii. The Phytoplitliora was present 
on all the pods sent and may be considered as the 
cause of the present epidemic in Trinidad. 
The same, or a closely allied species, appears to 
be the cause of the cacao-pod disease in Ceylon. 
PHYTOPHXHOEA OMNIVOEA. De Bar I/. 
" This fungus, as indicated by its specific name, 
is not fastidious in its choice of a victim, and has 
been recorded as attacking various species of plants 
belonging to the following genera: — 
Acer, Alonsoa, Abies, Cleome, Clarkia, Cereus, 
Epilohium, Fagus, Gilia, Larix, Lepidium, Melocactus, 
(Enothera, Picea, Pinus, Solanum, Senwervivum, Salpi- 
glossis. 
If the fungus is confined to the fruit of the cacao 
■ tree it is obvious that infection each season must 
necessarily be derived from some outside source, the 
■' spores for this purpose being iu all pi-obability often 
produced on diseased fruit or "shells" lying on 
the ground under the trees ; nevertheless, being able 
to leave on such a variety^of host-plants, infection of 
a plantation for the first time might every possibly 
be attributed to wind-borne spores produced on some 
' other kind of host-plant. This may appear to be 
poor consolation. However, it is well to be in 
possession of all known facts and possibilities in 
connection with the subject under consideration. 
' The life-bistory of the fungus is well known, having 
been carefully studied by De Bary, Hartig, and 
others, 
The conidial form of fruit appears as a very 
delicate white mould on the surface of the part 
attacked. The conidia or reproductive bodies are 
ovate or egg-shaped, being attached at the broad 
. end to a veiy slender stalk, which shrivels and liberates 
the conidium when mature. This condition of the 
fungus flourishes for a few weeks dui-ing the period 
of active growth of the host-plant ; and as the conidia 
are produced in immense numbers and in quick 
succession, and are dispersed by wind, insects, or 
rain, being washed from diseased parts of a tree 
to healthy parts, it can readily be understood why 
the pest spreads so quickly when once established. 
Conidia that happen to alight on young poda ger- 
■ minate at once, penetrate the tissues, and quickly 
■ produce a new centre of disease which furnishes 
more conidia in due time. 
Daring the period occupied in the production of 
the external form of fruit described above, the 
mycelium of the fungus spreads rapidly in the 
substance of the pod and gives origin to a second 
form of fruit imbedded iu the tissue of the pod. 
These reproductive bodies, known as resting-spores, 
remain for some months in a passive condition, 
and are eventually liberated by the decay of the 
pod : when they germinate, the bodies produced on 
germination being conveyed by wind to the young 
pods, germination in their turn, enter the tissue, and 
in a few days' time produce the conijial form of 
the fungus on the surface of the pod. 
Preventive Measures. — If it is ascertained that the 
fungus is not harboured by the other plants growing 
in the neighbourhood of the plantation, but is 
confined to the cacao trees, then prevention becomes 
an easy matter. It depends on having every diseased 
fruit collected and burned ; for the only possible 
cause of infection in the first instance must arise 
from the germination of resting spores developed in 
diseased pjds, and so Iook as these are allowed to 
remam on the ground under the trees the disease 
will continue to spread. But the fungus may also 
attack other wild plants, and thus become firmly 
established and defy extermination. 
The folio A'iog measures should be taken to combat 
the disease : — 
(1) Spray with Bordeaux mixture, commencing 
when the pods are quite young, and continuing at 
intervals of ten days. 
A dilute solution should first be used until its 
effect on the fruit and foliage is ascertained. A 
small quantity of dried blood should be dissolved 
and added to the mixture ; its adhesive property is 
much increased and fewer sprayings are required. 
(2) Remove all diseased fruit from the tree, if 
practicable, otherwise a continuous supply of conidia 
will be furnished until the fruit decays. Do not 
allow diseased fruit or " shells " to remain on the 
ground. All such should be collected and burned. 
(3) Endeavour to ascertain, by careful exami- 
nation, whether the fungus may not be also parasitic 
on other hosts ; it very frequently attacks seedlings, 
and would be recognised by the wilting of the 
attacked parts, and by the delicate white mould- 
like conidial form of reproduction." 
The disease had some years previously been observed 
in Trinidad, but no special study was made of it. 
It was detected by Professor Harrison in Surinam, 
and in Grenada by iilr. G. Whiifleld Srr)ith, but 
little notice however was taken of it until the end 
of the year 1898, when its rapid spread caused some 
alarm. 
The disease was observed to be most prevalent 
in places wheie the atmosphere was humid and where 
the pods had been allowed to rot beneath the trees, 
NECTRIA BAiNii, Massce- 
"This parasite causes semi-circular dark blotches 
to appear on the pods, the diseased portion becoming 
soft and watery. At a later stage the blotches be- 
come covered with a lovely interwoven layer o£ 
yellowish-rust coloured or orange mycelium which 
is studded over with the minute red perithecia or 
fruiting organs of the fungus. 
This parasite may possibly be quite rare, but 
great care should be taken to arrest any attempt 
on the part of the fungus to attack the trunk of the 
cacao tree, for as already stated the destructive 
canker disease of Ceylon is caused by a Nectria." 
" Nectria Bainii, iMassee — Perithecia gregaria. my- 
celio maculiformi flavo — ferrngineo vel aurantiaco 
insidentia, sphaeroidea. rubra, lanosa, denum supra 
calvescentia, 300-350 3licrons diam. A>,ci cylindraceo- 
clavati, breviter pedicellati, octospori, 80 — 90x7—9 
Microns Spores distichsB, oblongo-ellipticae, utrinque 
subacutEe, 1 septatee, 10 — 12 + 5 Microns hyalinae.' 
— Geo. Massee. 
" The Nectria appeared on two pods, and thia 
again possesses many points in common with the 
Nectria, which has caused such destruction to cacao 
trees in Ceylon by attacking the bark of the trunk 
and branches, as described b^ Mr. J. B, Can-atherB| 
