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PORTO RICO AGRICULTURAL EXPERIMENT STATION,
D. W. MAY, Agronomist in Charge,
Mayaguez, P. R.
BULLETIN No. 28.
Under the supervision of the STATES RELATIONS SERVICE,
Office of Experiment Stations, U. S. Department of Agriculture.
THE COFFEE LEAF SPOT
IN PORTO RICO
T. B. McCLELLAND, Horticulturist.
Issued December 14, 1921.
GOVERNMENT PRINTING OFFICE
VWAILUrj n. jKVArl urnTvt, UV~;ssn uo l( suw fnl&U4w$ ':&Mv!-
Offce of Emperiment Stations.
.I" .. r .K ."
D. W. MAY, Agronomist in rkarge :
T. B. MCCLtELLAND, Horticulturist.
W. V. TOWER, Entomologist.
L. G. WILLIS, Chemist.
T. IEGGER, Plant Breeder.
H. C. HENRICKSEN, Specialist in Farm Management.
J. O. CARRERO, Assistant Chemist.
W. P. SNYDER, Assistant i Plant Breeding.
J. A. SALDANA, Scientific Assistant in Horticulture. '.
C. ALEMAR, Jr., Clerkc.
.. .. .
.i t.. .E
THE COFFEE LEAF SPOT (STILBELLA FLAVIDA)
IN PORTO RICO.
Introduction...---------------- 3 Numerous hosts------------------ 7
The leaf spot and what it does-... 3 Observations subsequent to clearing 8
A Stilbella-infected plantation-- 5 Recommendations f or eradicating
Cleaning out a diseased section-- 6 Stilbella ------------- ---- 11
The purpose of this bulletin is to indicate means of controlling in
the plantations of Porto Rico the coffee leaf spot (Stilbela flavida)
(PI. I), which is the cause of heavy and continuous losses to the
coffee growers in Porto Rico, few of whom know anything of its
nature, or are able to distinguish it from any other spotting of the
leaves. The suggestions given for combating the disease are so
simple that it is believed they may be easily carried out by any
planter. There are many abandoned coffee lands in Porto Rico that
doubtless can again be made to produce at a profit if the grower will
follow the method outlined. The work required can be done, too, at
a minimum cost and with very little effort. Many of the ravaged
lands are not adapted to any other money crop at present, and, while
the coffee industry is not in flourishing condition in Porto Rico, it is
the most promising one for certain areas.
THE LEAF SPOT AND WHAT IT DOES.
The climatic conditions which seem most favorable for the growth
of the coffee tree (Coffea arabica) also foster the development of the
coffee leaf spot disease.
The disease is described in part by Fawcett 1 as follows:
In Porto Rico it is found principally in the higher altitudes, where it is
favored by excessive rainfall. Lower down it is found near streams and where
it is sheltered from winds and afforded a moist atmosphere during part of the
year. It is more dependent on moisture than other coffee fungi, being unable to
infect new leaves or to form new fruits except under conditions of extreme
1Porto Rico Sta. Bul. 17 (1915), p. 11.
nairiue projecuuons irom .JL to i nmiunetern long oi a yeuowismn Cur, ol w
ing at the end a head so that they resembleninute pins. This is the
tive or fruiting stage of the fungus... a4t 4 pot produces a continuous c:m
these hairs so long as weather conditions are favorable. The total. n
any time is small, and in an entire seapon-but from 20 to 50 are pro
each spot, judging from the number of old filament bases ., "he=,l'T
observed was 70 in a spot of 7 min~i eters diameter.. As tbe,
older, growth having stopped:for any season, such as. thoe aGait t
season, the diseased tissue falls away, leaving numerous circular opening
leaf. In other leaf diseases the dead tissue remains.
Sometimes the fungus attackia yoag ste&as4tr wlre it causes conspicuous
and so weakens the points affected that they are easily broken by the wind."|.
berries also are attacked, a slight discoloration f their grai i bifF'*
caused. ..... :
The microscope shows the filaments, which are soli4, nota l hAllUfSo
stated, to be made up of the fine fungus threads which, arp tmi g
in the upper part to form the head. The ends of the threat are wo
have sometimes been mistaken for spores when seen in'cross sdtiod 0.
scribed as such. No real spores have ever been found in An:y f tIi a nr
specimens examined. The fungus is distributed by the heads at the esi' a
filaments being caught by the wind or raindrops and piarrii to gmr--bl4pp
a process facilitated by the heads becoming loosened in: the older
through the formation of cavities or lacune" near the point of atta
The head is soon fastened to the leaf on which it happens :t ftAl
numerous threads which it sends out at the point of contact. Withhn leiki l
a week a dark circular spot is formed and new filaments appear,, and sew Aolo y
attached heads are formed on these by means of which the spread of thelp
is continued. Apparently this fungus has no other way of. propagtizgi
and the writer has not found any other stage of StilbeRi flwda, all inolu
tions into coffee with suspected forms resulting negatively. *
The injury to the trees is not so much in the actual amount of the leaf tisb
destroyed, although this may amount to one-fifth or even more of the
amount of the worst cases, but in the defoliations which take place
time. The diseased leaves drop sooner than those not affected, and
the weakened condition of the tree 'are not soon replaced.' After the f
attack the base of each tree may be seen to be' surrounded by a pile
leaves several inches deep. The disease never kills. the trees. :They
with scanty foliage and are able to put forth some new growth an i
small amount of berries each year. 'i' 4.......
The decrease in yield following an attack of the leaf spot Is n maiet '
experimental plat, where a record of the yield had been kept for komDt ..
it was found to be 75 per cent. .In this case the difference between ta
before and after the attack was such as accompanies the loss of the grete
of the foliage. *
Bul. 28, Porto Rico Agr. Expt. Station
FIG. I.-A SPOT OF STILBELLA FLAVIDA ON COFFEE LEAF, SHOWING FRUITING
BODIES. MAGNIFIED ABOUT FOUR TIMES.
FIG. 2.-A SPOT
ON LEAF, SHOWING FRUITING BODIES OF STILBELLA
HEAD OF FRUITING BODY OF STILBELLA FLAVIDA.
Bul. 28, Porto Rico Agr. Expt. Station.
FIG. I.-STILBELLA-SPOTTED LEAVES DROPPED PREMATURELY.
=. !X?.. :" ...=m== "
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DEFOLIATION CAUSED BY STILBELLA, LEAVES REMAINING
NEAR THE TIPS OF THE BRANCHES ONLY.
I I. 'W*f
q )Va., ve be.c.qbtained would indicate that the disease might
J on bated by removing the diseased leaves. No doubt the de-
2i pi ed Is as bad for the tree as that caused by the fungus,
6kk. i ee carefully done the newly formed leaves would remain free
except as they might be gradually reached from trees outside
lrea, The fact that the disease spreads comparatively slowly and
leaseded leaves are readily recognized make this treatment more easily
It would seem that this slow and apparently impracticable method
~I17r y of value in combating the disease where the cheaper labor used
a the6 plantations is available.
.| with Blordeaux mixture will exterminate the fungus if weather
pWappen to be favorable, but it is almost useless where the disease is
S prevalent because of the frequent rains. The fungus can not infect leaves
not moist much of the time; and when the leaves are dry, the time
SWould be most effective by adhering -best, the disease is at a
M i4:la:ny of the heads which happen to fall on such leaves do not
..ren if they adhere. The violent downpours soon wash the fungicide
th smooth upper surfaces of the leaves, where it must adhere to be of
Mt, Moreover, the hillsides are so steep in many places that only
sprayers could be used, and these only with difficulty. In case spray-
ei d to, it will be of most value when applied to the healthy trees
i"te'ased ones or to those less severely attacked, for the reason that
ilfl y will prevent the infection of the leaves to which it adheres, though
C: ioct in preventing the formation of new propagative bodies on the
St is .f.iterest to note that, although the coffee plant is the principal host
@e iiigus, numerous other plants are also affected to some extent. The
Wi i.tthrF fboad it on such unrelated host plants as the orange, mango, Begonia,
fVilrsi eras, several of the coitres (Commelina spp.), and guava (Inga vera),
a Wi b co de carro '(Veli sicyoides), and have noticed the spots, but not fruits,
on the yautia, banana, and also on several wild plants.2 The coitres, which
are perhaps most affected, and the ferns and other plants of low habit of
growth form in many places a continuous ground covering and catch the
greater part of the falling propagative bodies which escape the coffee leaves,
bpa ate hence peculiarly subject to the disease. They are apparently able to
# munuiicate it to unaffected plants of the same kind and doubtless also to
,healthy coffee plants. There were noticed places where the coffee was not
ed until several weeks after the ground plants had become infected.
.::; A STILBELLA-INFECTED PLANTATION.
In 1916 the station was consulted in regard to a plantation which
i as said to have produced in former times between 300 and 400
i:-intals of coffee. For some unknown reason, however, its produc-
tion became considerably smaller until in some years it did not ex-
ceed 10 or 12 quintals. A peon on the plantation reported the 1916
crop as 48 quintals and the 1917 crop as 28 quintals. The plantation,
which is located in the heart of the coffee country on the slopes of
one of the highest peaks of the island, was visited by the writer and
fomd to be in an almost abandoned state; in fact, the condition was
,pil rt. Rico Sta. Bul. 17 (1915), p. 13.
" ...... .... :. ...
takes many hours in the saddle tb reach the plantation, cons
he seldom, if ever, visits it, even to make an annuiul inspei
the plantation is accessible by mountain trails ,poz:l aid :4iq
hours distant from the nearest town and a, day's journey t
experiment station; and (4) that only a few of the cheapest tlae
laborers are employed on the plantation, and they ar:e'
CLEANING OUT A DISEASED SECTION. ,
The initial work in eradicating the leaf disease from the 1t
plat of this coffee plantation was done under the joint"
W. A. Mace, formerly agricultural technologist of th s
the writer, both of whom remained on the plantation e
30 to February 8, 1917. It was thought that the p1t seI ...ii
approximately 3,400 or 3,600 feet above sea level, the
estimated from a near-by point of known altitude.
The plat, while not an isolated one, offered so-m:
barriers against reinfection. The surface was s
two of the sides formed low convergent ridge
and 350 feet along the ridges, 90 feet along thei bo
313 feet along the lower boundary. Mida: lop
was crossed by .a footpath. .
The stand of coffee trees in some parts of ts plt was R8
in others it was very sparse. Above the footpath most of
had been abandoned and. was covered with underbrush .which a.
COFFEE LEAF SPOT IN PORTO RICO.
the process of clearing difficult and slow. Clearance was absolutely
itiCessary, however, because the upper stand of coffee overhung
Sthe better stand. No regular coffee planting was found above
V the plat, but coffee trees were scattered among the wild growth.
As a first step in the work of eradicating the disease, the coffee
Streets within the plat were cut to stumps approximately 6 or 9 inches
high, the larger wild growth was chopped down, and all the cut
material was either burned or removed from the field. The ground
was cleared as completely as possible of all miscellaneous living plants
and the shade trees were cleaned of vines and epiphytic plants so
that only the coffee stumps and the shade trees would be left in the
plat. The clearing was made to overlap the ridges in order that these
natural barriers might serve as much as possible to prevent rein-
.fection. Personal supervision of the completion of the work was
prevented by a labor strike, and it became necessary to leave to the
Speon in charge bf the plantation the removal of scattered banana
rootstocks and a large amount of the already cut growth from the
central lower part of the plat. He was also instructed to set closely
around the whole border three rows of banana trees to act as a barrier
against the adjacent diseased coffee trees.
A thorough destruction of the miscellaneous growth in the plat
was necessitated by the presence of a great number of plants which
act as hosts to Stilbella flavida. Many of these plants were un-
known to the men on the plantation.3 Those found and examined
included achiotilla, balsamo, bejuco de mono, bejuco de paloma,
berugillo, bruja, cadillos, camasey blanco, camasey cimarron, china,
helecho, guasabara, guayaro, guava, higiierillo, lechecillo, lengua
de vaca, moca, nuez moscada cimarrona, palo de cucubano, palo de
hueso, tostado, vinagrera, yerba hedionda. Coffee seemed to be
the favorite host, although there were several close seconds. It was
found that a great many fruiting bodies developed from a single
spot on the host plant bruja (Bryophyllum calycinum); and that
moca (Andira inermis) should be avoided as shade for coffee, where
the infection is to be cleaned out, because this tree may be a means
of distributing the disease. The danger of infection from orange
or guava (Inga vera) trees seemed slight. The orange trees were
almost clean, and the guava trees, though showing numerous spots,
bore only one fruiting body. Guama (Inga laurina) seemed en-
tirely free from infection and looked more vigorous than guava,
SThe plants are, however, well known in Porto Rico and mention is made of them in
order that the plantation owners may more readily know the host plants to be removed so
that the disease can be combated.
fwtboy- absolutOY e*yre ath 0W
*e trees olI d nthbaas lteron
1 shqvould be de0 lqW qeues" theWy *Me~the, mp 4Vngp
p~bbly be difficulQ nmprepss o the 'overiseer t4. telu
_Fw.ing Up. -,he- gycpti9 0ay~he
-lt, which 4owe4 doubflsoebtn.ri
box pots were S hoots. or renw rae4
ohr request was mde that the, plag b cleappujxL awar
dn, and on Augs 21 the plat was inspected. The sheo
cofe stumps wer thn froin 11 to WN41 Mg h. More thanWA'*
carefully eamined,. but they. showed o inwhave
in Septemb ter station sait to' i4e plntt o mA
NWch -the, oversee w as instructed to 1 ave p'lantdo
Va -nt 'laces. I 'ad Of -dbing as dificted, the over40 a 1o
obescattere closel6y in a small ariea.
insection was nad on January 6 Tepltw
m bleein recently cean'ed. more than '350 466fre'e t
nethe wh 16-. patiurl th6 perijhep"
Scarefully. nly, 1tree trees,. wih 0&e''r6f
wetern bcr e were lound& oigafw9i
ves' At the ei a year less6 thalq I p6rcent'of fh
infection; tha 'Was. bny sigh and ert
pltwhere inflec 6WOA6:tUbex e6t11 ThIs hoi ed
neswith which 6.dise'as'e .ha b;en lenid u
on August 1 DIN a keiist. *is nDuEd~eth l pd
l:-ned, and on I embep-1 th orhiseas,9i
pli hadntbe dad ndd it lvij tinib. ITs
rws appeared in llex, cjn.ooditi in ,484c W
FIG. I.-ONE YEAR'S GROWTH FROM COFFEE STUMP.
FIa. 2.-Two YEARS' GROWTH FROM COFFEE STUMP.
THREE YEARS' GROWTH FROM COFFEE STUMP.
COFFEE LEAF SPOT IN PORTO RICO.
; qp e;.han 400 trees were examined and only 7, or less than 2 per
qqat, showed any infection. These seven were all near the south-
wastern border and the infections were slight. Where only several
leaves were infected, they were removed; where a number were in-
fected, the tree was cut down. As in little more than 19 months from
the time of clearing absolutely no infection was found, except near
tbxe border where its reentry was to be expected because badly in-
fected trees were near by, the elimination of disease through the
oqaga clearing of the plat was considered to be all that could be
; When the fifth inspection was made on November 12, 1919, the
plat was found to need cleaning. The renews were in splendid shape
and averaged approximately 6 feet high (P1. III, fig. 2). Some of
them were 9 feet or more in height. About four months prior to this
date the overseer on his own initiative set some 600 or more young
pfee trees throughout the plat below the path and a few above it
at the west side. Many of these had been brought in from the dis-
Seased coffee outside the plat, and their leaves were riddled with Stil-
bella spots. Inasmuch as these trees had not only been carried
Through the planted area with every chance for thousands of fruiting
bodies to drop and establish themselves on all sides but were allowed
to remain there for some months as centers of infection, no further
control over the disease could be expected to result from the original
The renews of more than a hundred coffee trees were examined
with great care. Most of these were above the path where the over-
seer's replanting would not affect them, and some were below the
path. With the exception of a single spot on one leaf, no other in-
fection was seen on any of these. This tree was just below the path,
into which its branches extended. Near it on both sides were young
trees which the overseer had set. Below it was a small volunteer
seedling which had one spot on one leaf. Some infection was ob-
served in the V-shaped corner at the south where the wind was evi-
dently bringing in fruiting bodies from the diseased plants outside.
During the first week in December, 1919, an attempt was made to
clean out such disease as was visible, and a laborer who had worked
for some years with the station pathologist was sent to the plantation.
He reported 829 old trees in all. Of these, 695, or 83.8 per cent,
showed no Stilbella spots; 75 trees, or 9 per cent, showed not more
than two spotted leaves; and 59 trees, or 7.1 per cent, showed three
or more spotted leaves. Of this last group, 12 trees were within 2
to 4 feet of the border of the plat. Above the path he found but
two old trees which showed any infection and these were near the
no infection. However, on other 'trees cattereldlri'
Stilbella-spotted leaves wmere fdutnd. In some inst Aiiee t
leaves out of many hundred showed disesee- spots; iOeriA.st.9tI
approximately a third of the branches boi sp6ttd l~dit ik~A
reinfestation was to be expected as the result ofth' ha bM i
tion given by the overseer some 16nidnthsi befoe.. eid-ebt LaA 8
also furthered through the ptesenfe on thb 46d6&covel 4d lif00 iiaf
host plants, which conveyed the leaf disease from ond'~$4bM ail
COFFEE LEAF SPOT IN PORTO RICO. 11
RECOMMENDATIONS FOR CONTROLLING STIBELLA.
S Tho degree of control which was maintained over this disease under
very adverse circumstances demonstrated that it could be handled
easily by destroying the host plants and after that by maintaining a
If Stilbella is to be controlled on an infected area the work will
be simplified by first establishing clean cultivation. This can be done
by weeding the area frequently. There should be little or no diffi-
culty in keeping weeded a section that is heavily shaded by the coffee
and shade trees. After the grass and weeds have been killed, the
coffee trees should be cut away 6 inches above ground and the stump
Left with a clean diagonal cut which will shed the rain. This should
be done as soon as the crop has been removed, so that full advantage
Scan be taken of the dry season. The felled trees may be chopped up
S just where they fall. The control of the disease depends on the thor-
oughness with which the host plants are destroyed. Any careless
overlooking of diseased plants may mean speedy reinfection of the
Coffee. Subsequent work consists in keeping the coffee and adjacent
areas free from weeds which may harbor the disease, and also in
maintaining a sharp lookout for reinfection in order to remove any
disease as soon as it appears.
In vicinities where conditions are favorable to Stilbella, coffee trees
that have long been severely affected would be greatly improved were
they cut to a low stump and forced to develop a new trunk. In the
S experiment discussed in this bulletin two entire crops, most of a third,
Sand possibly part of a fourth crop were lost through felling the
coffee trees. If maintained free from disease the new growth should
soon yield more than enough to compensate for this loss of crop from
Sthe old diseased trees.
Good results are much more certain to follow where all Stilbella-
infected sections of a plantation-are cleared in the same season than
where some sections are left to be worked over later. On many plan-
tations this can be done. Where, for economic reasons, it is imprac-
ticable to work over the whole diseased area in one season, the most
isolated and the most elevated sections affected should be cleaned first
in order to leave no diseased tracts overhanging the cleaned ones. All
natural barriers, such as ridges, uninfected plantings of food crops,
or pasture land, should be taken advantage of; and where no natural
barriers exist, a strip of coffee may be destroyed along the edge of the
section to be cleaned and rows of bananas planted closely enough to
offer a barrier against the diseased plants outside. Care should be
exercised to reduce to a minimum the passing of pickers and laborers
From diseased into disease-free sections.
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UNIVERSITY OF FLORIDA
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