THE DISEASES OF COFFEE.
Though coffee in Mysore is liable to two diseases, and to the attack of
one insect, these, when the cultivation is good, and the shade suitable in
kind and degree, are not likely to cause any uneasiness in the minds of
the planters. But it is, of course, necessary to go carefully into the
whole subject of these diseases and the insect attack, in order to bring
out fully the steps that should be taken so to cultivate and shade the
coffee as to render these evils as innocuous as possible, and I have
therefore, in addition to my own knowledge, taken pains specially to
procure from two planters of long practical experience their views. The
views, I may say, of Mr. Graham Anderson as regards leaf disease are
particularly valuable, as he has paid much attention to the subject.
Leaf disease is the common name given to the attack of _Hemeleïa
Vastatrix_, a fungoid plant which distributes its spores in the form of a
yellow powder. These alight on the leaves of coffee, and in weather
favourable to the fungus, will germinate in about a day, and the fungoid
plant then roots itself between the walls of the leaves. After the plant
has completed its growth, which it generally does in about three weeks,
more spores are produced to fly away with the wind, or be scattered by the
movements of the coolies amongst the coffee, and thus the disease spreads.
A great deal, of course, has been written about it, and those who desire
more particular information may refer to Mr. Marshall Ward's report on
coffee loaf disease in Ceylon. It is sufficient to say here that when the
attack is severe the tree is deprived of its leaves, or of a large number
of them; that much injury to the crop results; and that both the tree and
the soil are heavily taxed in replacing the foliage that has been
destroyed.
Leaf disease has probably existed[56] in Mysore as long as coffee has, but
was, from the small amount of it, so entirely unnoticed, that, when I
wrote my chapter on coffee in the "Experiences of a Planter," more than
twenty-two years ago, I had never heard of it, nor, I am sure, had any of
my neighbours. A trick, however, I once played on Mr. Graham Anderson's
cousin about thirty years ago, enables me to trace it backwards so far
with certainty. On coming through his plantation on one occasion, I picked
oft a very large yellow coffee leaf, and placed it below the first of
several plates with the aid of which he was helping his visitors. When the
servant lifted the first plate, there was the leaf, and I said to my
friend, "There are your golden prospects." Many years afterwards Mr.
Graham Anderson recalled the incident to my memory, and said, "That was
the leaf disease." But it was not till leaf disease appeared in Ceylon in
a severe form that our attention was called to the subject, and since then
leaf disease has undoubtedly increased, and, in the opinion of one of the
two experienced planters I have consulted, has caused much loss directly
and indirectly, while the other informs me it has caused much loss on some
estates. But I confess my own observation causes great doubts in my own
mind as to whether the losses of leaves which planters attribute to leaf
disease are entirely owing to that cause, and I was much struck with what
Mr. Reilly, of Hillgrove Estate, Coonoor, said to me on the subject; and
when we were discussing leaf disease in general, he observed that it was
often said to be the cause of leaves falling off, when their doing so was
really owing to an over heavy crop of coffee. Then with our dry east winds
many leaves become yellow and fall off, and some become so because they
have been injured by the pickers, others from rot, and others from old
age, and all these leaf losses are commonly put down to leaf disease, so
that, taking all these points into consideration, I find myself quite
unable to determine, even approximately, the amount of loss arising from
_Hemeleïa Vastatrix_.
But of one thing, however, I do feel absolutely certain, and that is, that
when the land is well cultivated, manured, and judiciously shaded with
good caste trees, leaf disease may be reduced to such a degree that we
need not trouble ourselves about it, and I feel equally sure that the most
important of all the agents for controlling and limiting the disease is
the shade of good caste trees. And as to the effect of shade upon
_Hemeleïa Vastatrix_, I made particular inquiries when visiting estates in
1891 on the slopes of the Nilgiris, and conversing with planters on the
subject. One manager went so far as to say that there was no leaf disease
under the shade trees. Mr. Reilly, of Hillgrove Estate, said there was
much less leaf disease under the shade trees. Another planter of great
experience told me that leaf disease begins on the coffee in the open, and
then spreads into even the finest trees under shade, but that those are
affected in less degree. "In the end," he said, "You see the estate all
yellow, but with green patches of coffee under the shade trees." In short,
I found that all the planters I consulted were agreed in saying that there
was but a small amount of leaf disease under the shade trees. The estates
on the Nilgiri slopes have been originally all in the open, but latterly
shade has been encouraged on some estates, but not to a degree which in
Mysore would be called shade. However, the shade was quite sufficient, as
we have seen, to illustrate the important fact that shade can control leaf
disease. And as shade can control leaf disease, I need hardly say that it
is of the utmost importance (just as it is as regards Borer), to carefully
fill up at once all spots where shade is deficient, because this
deficiency encourages leaf disease, and forms a breeding ground for spores
to fly into the surrounding coffee. Open spots here and there may not
strike one at first sight as being of much importance, but if they are all
added together, the planter will see that they will amount to a
considerable area of land, and quite sufficient, at any rate, to inoculate
his plantation with leaf disease.
The reader will observe that I have said that leaf disease may be reduced
within practically speaking harmless limits if the coffee is judiciously
shaded with good caste shade trees, and I would call particular attention
to the term good caste trees, because bad caste shade trees will not
control leaf disease. On the contrary, Mr. Graham Anderson informs me that
he has seen worse leaf disease under a dense covering of bad shade trees
than he has in the open, and he also informs me that, though shade is the
backbone of our success in Mysore, he has had more misfortune from all
causes when his estate was under the heavy shade of bad caste trees than
he has ever had since, though many places are not yet properly covered
with the good kind of shade trees which he had planted to take the place
of the bad ones he had removed. I am much indebted to Mr. Graham Anderson
for information on the subject of leaf disease, and he has been kind
enough to enumerate the following conditions under which leaf disease is
liable to occur in the cases of good soils under good shade:
"In the case of good soils under good shade trees," writes Mr. Graham
Anderson, "leaf disease is liable to occur under the following
circumstances, or at the following times:
"1. From the soil being saturated at some critical period of growth,
particularly just when secondary growth commences in September.
"2. During the time when the plants are maturing a heavy crop.
"3. After the plants have been exhausted by ripening a heavy crop.
"4. After heavy weeds--particularly if late in the season.
"5. After a heavy digging where roots have been cut.
"6. After pruning without manure having been applied, or from want of
digging.[57]
"7. Even after manuring when the trees have large succulent roots in an
immature condition--generally a sign that fibrous surface roots are
deficient, and that large, deep-feeding roots are present in excess.
"8. After large quantities of green or rotting weeds have been deeply
buried, or large quantities of acid, unrotted, or forcing manures have
been applied.
"Leaf disease is also liable to occur:
"1. In poor gravelly soils, and on land which has caked in the hot
weather, or become unmanageable during rain.
"2. On land where ill-balanced manurial preparations have been used.
"3. In soils suffering from a deficiency of the available supply of
phosphates and alkalies.
"4. Under unsuitable shade trees."
Now it is to be observed that these are preventable causes, or
aggravations of leaf disease, and, if carefully attended to, the planter
will have little to apprehend from leaf disease. Mr. Anderson, in his
communication to me, lays, and very rightly, particular stress on the
maintenance of the physical condition of the land and its state of
fertility. And it is satisfactory to find that he is exactly confirmed by
Mr. H. Marshall Ward in his third report (dated 1881) on coffee leaf
disease in Ceylon, and he points out (p. 3) that "Leaf disease appears to
affect different estates in different degrees on account of varieties in
soil, climate, and other physical peculiarities."
"But," he continues, "I would draw particular attention to this. Careful
cultivation and natural advantages of soil, climate, etc., enable certain
estates to stand forth prominently, as though leaf disease did not affect
them, or only to a slight extent, while poor nutrition, the ravages of
insects, etc., have in other cases their effects as well as leaf disease."
Or, in other words, he states that, as was suggested to me by Mr.
Reilly--a planter of long experience near Coonoor on the Nilgiris--that
much loss of leaves, which has been attributed to leaf disease, is often
due to other causes.
Mr. Brooke Mockett--one of the planters previously alluded to--informs me
that "Leaf disease is certainly worst (1) on trees that are cropping
heavily, (2) on trees that have been severely pruned (heavy pruning being
ruination in my opinion), (3) on plants under bad caste shade trees (these
plants it seems to cripple), and (4) on plants in the open."
It is worthy of note that the Coorg plant is not nearly so liable to
attacks of leaf disease as the original Mysore Chick plant. I have seen a
tall plant of the latter variety heavily attacked, while a Coorg plant
partly under it was only slightly attacked on the side next the Chick
plant, and hardly at all on the side not under the Chick plant. I observe,
too, from the Planting Correspondent's Notes in the "Madras Mail" of
January 30th, 1892, that the same thing has been observed in Coorg, and
that occasional Mysore plants, which had by some accident found their way
into the Coorg coffee, got the disease first, and that it then spread into
the surrounding coffee.
It should be borne in mind that leaf disease does not kill the tree, but
only injures it, and diminishes its powers by depriving it of much of its
foliage, so that there is nothing alarming in leaf disease when it is
controlled by good management of the tree, and good shade, cultivation of
the soil, and manuring; and the only case I can hear of where anything
like permanent injury has occurred, is where the disease has existed under
the shade of bad caste trees. But it is far otherwise with the justly
dreaded Borer insect, which, however, can, as we shall see, be effectively
controlled by good shade. To the attacks of this insect I now propose to
direct the attention of the reader.
The too well-known coffee Borer is a beetle, about as large as a horsefly,
which lays its eggs in any convenient crevice, and generally, it is
supposed, near the head of the tree, in the bark, or wood of the coffee
tree. After the larvæ are hatched they at once burrow their way into the
tree, where they live on the dead matter of the inner or heart-wood of the
stem, and there they reside from, it is supposed, three to five months,
till their transformation into winged beetles. Then they bore their way
out of the tree, and fly away to carry on their mischievous work. This
insect has been declared to be, by Mr. John Keast Lord, "a beetle of the
second family of the Coleoptera Cerambycidæ, and to be closely allied to a
somewhat common species known as the wasp-beetle (_Clytus avietis_),
which usually undergoes its changes in old dry palings." And in a
collection made by M. Chevrolat in Southern India, and now in the British
Museum (at least it was so in 1867, when Mr. Lord investigated the point),
a specimen was found, to which the name of _Xylotrechus quadrupes_ was
attached. This Borer, like the leaf disease, has probably always attacked
coffee, but the earliest probable notice of it is to be found in Mr.
Stokes's Report on the Nuggur Division of Mysore, in about 1835, where he
observes that coffee trees in dry seasons often wither and snap off
suddenly at the root. The cause, or probable cause of this he does not
state, but there can be little doubt that the Borer had attacked the trees
alluded to. Since then the Borer seems to have attracted little or no
attention till towards the end of 1866, but about that time, and during
the three following years, an alarming attack of Borer took place, and
inflicted immense injury on plantations, and there can be no doubt that
this was in a great measure owing partly to insufficient shade, and partly
to bad caste shade trees, accompanied by dry, hot seasons, which were
favourable to the hatching of the eggs of this destructive insect. But
since then much attention has been paid to shade, both as to quantity and
kind, and the Borer may now be regarded as an insect which can with
certainty be held in check if the land is properly shaded with good caste
trees. And I say good caste trees, because bad caste trees encourage
Borers, and Mr. Graham Anderson, who has had a very large and disagreeable
experience of the effects of bad caste trees, informs me that he has "seen
worse Borer under dense _bad_ caste shade than in open places in good soil
on northern slopes." "Some bad shade trees," he continues, in his
communication to me on the subject, "keep the coffee in a debilitated
state. They allow it to be parched up in the dry weather, and they smother
it in the monsoon. They rob it of moisture and manure with their myriads
of surface-feeding roots, and prevent dew and light showers benefiting the
plant. I do not fear Borer under well-regulated shade of approved
descriptions. Renovation pits left open in the hot weather, large
clod-digging in a light soil even under fair shade, weeds left standing in
dry weather; all these, by increasing evaporation, tend to cause increase
of damage from Borer. A hard caked surface, or a compact, undug soil is
equally bad. Rubbing and cleaning the stems is a valuable operation,
because it removes rough bark in which eggs may be deposited, and
contributes to the health of the tree. The prompt removal and burning of
all affected trees, properly arranged shade of selected varieties,
frequent light stirring of the surface soil, having well arranged shoots
distributed all over the coffee trees, not opening the centre of the trees
too much, and keeping the trees succulent and vigorous by culture and
manure, may be at present classed among the best remedies for the Borer
pest." In other words, he would say that the Borer loves dry wood. Keep
your coffee tree green and succulent and well shaded, and you have little
to fear from it.
I have also obtained the opinion of Mr. Brooke Mockett, who informs me
that "Borer is certainly as destructive under bad caste trees as in the
open." "Borer," he continues, in his communication to me on the subject,
"is always much worse in land where there has been a burn than in unburnt
land. It is also bad in rocky and stony places. In good soil, where there
has been no burn, I have never had Borer severely, even though for a time
there has been no shade whatever. I do not fear Borer now that such an
excellent system of shade raising has been discovered. Rubbing stems once
in about three years I look upon as of great use."
I too have had great experience of Borer, and agree with what my friends
have written on the subject, with the exception of what Mr. Graham
Anderson has said as to the advisability of promptly removing and burning
all bored trees. This I am aware is the common practice, but I have never
carried it out on my property, and yet, though the trees were riddled with
Borer in the great Borer years, and I have had since then a fair
proportion of it on some part of my property, I believe that no estate has
less Borer now. Instead of removing the bored trees I removed the Borer
itself with the aid of the shade of good caste trees, and especially, I
believe, by paying strict attention to what I have particularly enforced
in my shade section--the prompt filling up of every spot in the plantation
that called for more shade. For it is in such spots that the Borer first
locates itself, and then it spreads to other dried up trees in the
plantation. There is little use, I think, in removing the affected trees.
You must remove the cause of their being affected, because, if you do not,
the _sound_ trees that are insufficiently shaded will in time be affected:
and then it must be remembered that the Borer is a winged insect which, as
long as you leave suitable ground for it, will be sure to make its
appearance. Out of curiosity I lately cut down and carefully examined a
coffee tree which I could see, from the appearance of the bark, had once
been heavily bored, but which I felt certain had no Borer now, nor any
recent attack of it. The tree I found, after a careful dissection, had not
a sign of Borer present in it, nor any sign of a recent attack, and yet in
years gone by it had been heavily attacked and bored literally from end to
end of the stem. The explanation was that the land had formerly not been
sufficiently shaded, while now the shade is ample. The Borers had then
left the trees, and their descendants had either not thought it worth
while to lay any eggs on them, or the eggs had, from the lowered
temperature caused by the shade, become addled. Many years ago I remember
cutting down a fine coffee tree, when the round gimlet-made looking hole
through which the insect makes its escape was plainly to be seen, when I
found that a single Borer had drilled a hole down a part of the centre of
the tree, then passed into the fly state and left the tree. It was a fine
succulent and nourishing tree, and would, in all probability, have not
again been attacked. To remove, then, all attacked trees, as some planters
do, seems to me to be a great waste. To do so will not prevent other
Borers arriving from some quarter or other to continue the deadly work;
but shade, if it does not prevent their arrival, either prevents the
insect from laying its eggs, from instinctively feeling that the ground is
unsuitable for their being hatched, or causes the eggs to become addled.
But whatever the cause may be, it is certain that succulent trees in well
shaded land will not suffer from Borer, while it is equally certain that
coffee trees in a dried up state, and with either insufficient shade, or
shade of bad caste trees over them, are certain to be attacked by Borer
again and again, and will eventually be killed.
I turn, lastly, to the consideration of a disease in coffee which is
popularly known by the name of rot, and scientifically as _pellicularia
koleroga_, a fungoid plant which crawls over the leaves and seals up their
breathing pores, till at last the leaf dies, as man does, from want of
breath. On one of my estates we have had a considerable experience of it,
and, whatever may cause rot, I feel sure that what aggravates it, and
causes it to be very injurious, is the want of free circulation of air
over the land, and through the coffee trees; and I am the more convinced
of this because we have found rot worse in the open, and where there was
little undecayed vegetable matter present in the soil, than in rather
thick shade with abundance of undecayed vegetable matter on the surface.
But in the latter case the land is on a rather high ridge exposed to the
constant winds of the south-west monsoon, while in the former case the
land was in a hollow under a hill which lies between it and the west--a
hollow completely sheltered from the wind. And it is in such sheltered
spots that we find rot worse, and quite independently of the presence or
absence of shade or of vegetable matter lying on the land. To check rot,
then, the free circulation of air is necessary both over the land and
through the plant. Much may be done in the first case by judiciously
opening channels for air through the shade trees so as to admit a free
circulation of air into hollows, and much in the latter by freely handling
out the centres of the trees which, in the monsoon, and especially in
hollows, are apt to grow a superabundance of young wood, which chokes up
the centre of the tree and thus hinders the free circulation of air. The
soil, too, is often excessively saturated in these hollows, and, where
this is the case, the land should be surface drained. Though I have not as
yet adopted the plan of sweeping up and putting into the manure heap, or
burying with a little lime added, the numerous dead leaves that are apt to
drift into hollows, I feel sure that either of these plans would be
attended with advantage, by lessening damp, and allowing a free
circulation of air over the land. I am confident, I may add here, that the
removal of the lower branches of the coffee trees, branches which in any
case bear hardly anything in well-shaded land, would be of great advantage
in lessening the damp in the plantation, and so diminishing the causes
that promote rot.
With reference to rot, it is of great importance to thin out young wood as
early as possible, so that, when the rot season arrives, the trees may
have a moderate amount of well-matured young wood, with fully-developed
hardened leaves, instead of a largo number of small succulent shoots
covered with succulent leaves, which are very apt to be rotted bodily
away. And the importance of this is equally great with reference to leaf
disease, and Mr. Ward, in his "Report" (p. 15), points out that pruning
and manuring should be so timed that the tree may have, at the beginning
of the wet weather, mature wood and leaves, and the whole of his
observations on this head point to the conclusion that manuring ought to
be carried out at the close of the monsoon, and that pruning, which
encourages the growth of much young wood, should be limited as much as
possible to the removal of utterly useless, worn-out wood. Under the head
of pruning and handling, the reader will find some remarks with reference
to the important subject of the best time for pruning so as to limit rot
and leaf disease.
I am glad to say that I have no other pests to chronicle as regard Mysore
estates, but as estates on the Nilgiris sometimes suffer from green-bugs,
I give the following treatment, which was discovered, and has been
effectually used by Mr. Reilly of Hill Grove Estate, Coonoor, who has
kindly permitted me to publish the recipe.
For every 30 or 35 gallons of water take a bundle of wild merang (_Leucas
zeylanica_ or (Kanarese) Thumba Soppu) plants about two feet in diameter,
and, after removing the roots, boil it for about four or five hours, and
let it cool all night, and in the morning apply the decoction to the
coffee trees affected, with the aid of a garden syringe. The trees should
be well syringed, and it is advisable to give the tree a second
application. The refuse of the boiled plant should be scattered on the
ground around the stem of the tree.
This prescription might probably be useful in the case of garden plants or
shrubs which have been attacked by insects.
FOOTNOTES:
[56] Mr. Reilly, of Hillgrove Estate, Coonoor, told me that he had first
noticed leaf disease about twenty-six years ago. It commenced low down on
the coffee on the Coonoor Ghaut, and then came gradually up the Ghaut.
[57] A planter on the slopes of the Nilgiris gave me a well marked
instance of leaf disease being increased from want of digging, when there
was a good opportunity of contrasting the dug with the undug soil.