1.48 Isuaed May 8, 1911.
PORTO RICO AGRICULTURAL EXPERIMENT STATION
D. W. MAY, Special Agent in Charge.
Mayaguez, January, Ignx.
Bulletin No. 10.
INSECTS INJURIOUS TO CITRUS FRUITS
AND METHODS FOR COM-
W. V. TOWER,
Entomologist, Porto Rico Agricultural Experiment Station.
UNDER THE SUPERVISION OF
OFFICE OF EXPERIMENT STATIONS,
U. 8. DEPARTMENT OF AGRICULTURE.
GOVERNMENT PRINTING OFFICE.
PORTO RICO AGRICULTURAL EXPERIMENT STATION.
[Under the supervision of A. C. TRUE, Director of the Office of Experiment Stations,
United States Department of Agriculture.]
WALTER H. EVANS,
Chief of Division of Insular Stations, Office of Experiment Stations.
D. W. MAY, Special Agent in Charge.
J. W. VAN LEENIIOFF, Coffee Expert.
W. V. TOWER, Entomologist.
P. L. GILE, Chemist.
C. F. KINMAN, Horticilturist.
E. G. RIrzMAN, .Inimal Husbandmain.
G. L. FAWCETT, Plant Pathologist.
T. B. McCLELLAND, Assistant horticulturist.
W. E. HESS, Expert Gardener.
C. ALEMAR, Jr., Stenographer.
LETTER OF TRANSMITTAL.
PORT RIco AGRICULTURAL EXPERIMENT STATION,
Mayaguez, P. R., January 27, 1911.
SIR: I have the honor to transmit herewith a manuscript on the
subject of Insects Injurious to Citrus Fruits and Methods for Com-
As the growing of citrus fruits is rapidly forging ahead and
destined to be one of our leading industries, and as any information
looking to its betterment by the employment of the most intelligent
efforts in its promotion will be of value, the issuance of this bulletin
I respectfully recommend that this manuscript be issued as Bulletin
No. 10 of this station and that it be published in both English and
Respectfully, D. W. MAY,
Special Agent in Charge.
Dr. A. C. TRUE,
Director Office of Experiment Stations,
U. S. Department of Agriculture, Washington, D. C.
Recommended for publication.
A. C. TRUE, Director.
Secretary of Agriculture.
Relation of insecticides to insects ...........................-..........-... 8
Orange-leaf weevil (Diaprepes spengleri).................................. 8
Small orange-leaf weevil, or "green bug".............................. 9
May beetle (Lachnosterna sp.) ......................... .................. 10
Orange dog ..................................... ................ .... 10
Brown ant (Solenopsis geminata) ....................................... 11
White fly (Aleyrodes howardi) .......................................... 11
Red spider........ ................. ................. .... .............. 12
SRust mite ................................ ........ .............. 12
Purple scale (Lepidosaphes beckii) ........... ........................... 13
White scale (Chionaspis citri)............................................ 14
Florida red scale (Chrysoinphalus aonidum) .............................. 14
Hemispherical scale (Saissetia hemisphwrica)..................... ........ 15
Beneficial fungi ..................................... ................... . 15
Methods of introducing beneficial fungi................................. 15
W indbreaks .............................................................. 16
Scarred fruit ......................... .......... ............. ......... .. 18
Notes on spraying .................... .. ................. .... ............. 20
Covering for operators ................. ....................... ......... 20
Spraying machinery................................................... 21
Agitators................. .. .. .................... ........... 22
Extension rods ....................... ............... ....... .......... 22
Nozzles ...-...............------............... ... ....... -------------22
Insecticides and fungicides ................................................ 23
Insecticides for biting insects ................................ ........ 23
Paris green ...................................... .... ....... ..... 23
Arsenate of lead ..................... .. ...... ...................... 23
Arsenite of lime ................. ...... ........... .. ....... ..... 23
Insecticides for sucking insects ........................................ 24
Miscible oils...............................- ............... .-..... 24
Directions for making miscible oils .............-..........-... 26
Kerosene and crude-oil emulsions .................................. 27
Kerosene emulsion ................................... .............. 28
Kerosene and crude-oil emulsions with crude carbolic acid........... 28
Crude-petroleum emulsion with sal soda............................ 29
Lim e sulphur .......... ... .... ..... .... .... ........ ....... ...... 29
Caustic soda and sulphur wash ........................-.....-..: .. 30
Formula for emulsion for ants ............... .. .........- ....... 31
Bordeaux mixture.................... ........... ........... 31
Hints on purchase of ingredients ....................................... 32
Summary........---- ........--...........------ -...- ------- ------.........- 32
Emulsions--................-------------- ..... ----------- ........... 333
Time of spraying ................. .. .... ... ........ .... ............. 334
W indbreaks ................. ........ .......................... 35
Spray pumps .............. ..... ...... ................. ............... 35
PLATE I. Fig. 1.-Ants' nest at base of orange tree. Fig. 2.-Injuries to fruit
by ants and wind............................................ 10
II. Fig. 1.-Black fungus on white scale (Chionaspiiscitri). Fig. 2.-Red-
headed fungus (Spherostilbe coccophila) on purple scale........... 14
III. Fig. 1.-Hemispherical scale (Sassetia hemisphsrica). Fig. 2.-
White fungus (Sporotrichum sp.) on hemispherical scale.......... 16
IV. Fig. 1.-Permanent windbreak, timber. Fig. 2.-Permanent wind-
break, mango trees............................................. 16
V. Fig. 1.-Temporary windbreaks, pigeon peas and sugar cane. Fig.
2.-Temporary windbreaks, bananas and pigeon peas............ 18
INSECTS INJURIOUS TO CITRUS FRUITS AND
METHODS FOR COMBATING THEM.
The object of this bulletin is to describe the life history of some
of the various insects injurious to citrus trees, and also to give the
various insecticides which are being used and their effect on both
trees and insects.
For years the planters of Florida have been spraying their trees
with various emulsions to keep their fruit clean and trees healthy.
The time has arrived .for planters in Porto Rico to pay more atten-
tion to the appearance of their fruit if they desire to realize top-
market prices. In order to grow clean fruit more spraying at the
proper time is necessary. The experiment stations of the United
States have shown that beneficial results may be obtained by spray-
ing. Orchards that produced practically nothing but worthless fruit
have been sprayed, with the result that 90 to 95 per cent of their
fruit is perfect.
Previous to 1909 very little cultivated fruit had ieen shipped from
this island, as most of the groves were young and the fruit poor in
quality, little attention having been paid to its appearance. Now.
that the groves are maturing, more attention will have to be given
to the appearance of the fruit in order to obtain a higher market
standard. This can be done by carefully watching for the appear-
ance of insects. Spraying should be done as soon as the insects ap-
pear, so that they will not multiply and ruin the crop. Planters
should realize that systematic spraying is important, and that the
work must be done thoroughly. Thorough work not only implies the
use of specific kinds of insecticides, but also special care in their
There are a number of different kinds of insects which have become
troublesome to citrus trees. Their successful combating depends
largely on an intimate knowledge of their habits, life history, and
physical characteristics. Without such knowledge it is impossible
to anticipate an attack by them or to know the most effective means
for their immediate elimination without injury to the trees, and
frequently to the fruit itself. Parasitic factors are often more desir-
able in eliminating a pest than resort to treatment with insecticides,
provided the parasite itself does not become a pest.
RELATION OF INSECTICIDES TO INSECTS.
Various kinds of insecticides are used for the different classes of
insects because of structural differences in their mouth parts. There
are two types of mouth parts-in one type they are constructed for
chewing, while in the other they are drawn out into a tube which is
inserted into the plant tissue to remove the juices by sucking. In-
sects of the former are more easily killed by stomach poisons and of the
latter by contact poisons, while some of both may be kept away
from plants and trees by means of repelling agents.
Stomach poisons are generally used on insects with chewing mouth
parts, as, for example, the mole cricket and May beetle, although
there are exceptions to the rule. Paris green and arsenate of lead
are generally considered as the most efficient remedies of this class.
They are usually sprayed upon the leaves that they may be swallowed
with the food.
Contact poisons are generally used on insects with sucking mouth
parts, of which the scale insects, plant lice, and the white fly are
examples. Stomach poisons are of no avail against such, because
they thrust their beaks into the tissues of the plant and thus avoid
the poison on the surface. Contact poisons, on the other hand, fill
up their breathing pores and smother them or cause death through
irritation. Various emulsions made with carbolic acid, kerosene,
crude oil, boiled lime sulphur, and miscible oils kill insects by
Repelling agents can be used to advantage on some insects. In
fact, some of the aforementioned agents, as carbolic acid and kerosene,
serve this purpose, but when used for repelling purposes their prepa-
ration is more simple than when used as emulsions. Ants are some-
times successfully kept away from plants and trees by means of
repellents, although their destruction is. more certain with contact
poisons applied in their nests.
The orange-leaf weevil appears during May, June, and July, and
again in November, there being two broods a year; but a few of these
insects can be found among the orange trees during the other months
of the year.
The larva of this insect is a white grub, which feeds on the roots of
the orange. In a few cases it was found damaging the trees to such
an extpet that the leaves turned yellow and dropped off. This insect,
however, is not so destructive as the May beetle or its larva, the
"caculo." The adult has other hosts, as the guava, avocado, mango,
The adult weevils vary in size and color markings. General color
black, with white and yellow markings; head and snout black, pitted
with white. The black markings on the elytra, or wing covers, are not
constant. The lines run together, in many cases producing an irregu-
lar black surface. The white markings on the thorax and abdomen
are also variable, many specimens of both sexes having been found in
which these markings were lost or greatly modified. The male, as a
rule, is much smaller than the female. They average about as fol-
lows: Female, length one-half to three-fourths inches; male, length
one-half to five-eighths inches.
When this insect appears, spraying should be resorted to with arse-
nate of lead, 4 pounds to 50 gallons of water. If there is a great deal
of scab in the groves it is recommended that a fungicide be applied
with the insecticide. Bordeaux mixture may be used as such with
arsenate of lead, since these two solutions mix readily and can be used
as one spray.
In using Bordeaux mixture and arsenate'of lead one should be sure
that the scale insects are well under control before applying this com-
bination insecticide and fungicide, as the Bordeaux kills all the bene-
ficial fungi that prey upon the purple scale.
SMALL ORANGE-LEAF WEEVIL, OR GREEN BUG."
The small orange-leaf weevil, or green bug," was first noticed
during the winter of 1908. It was found in the San Juan district and
near Arecibo. It has been observed only in groves planted in sandy
soils. Its life history has not been completely worked out.
In 1908 the insects appeared in January and February, and by the
1st of March all the beetles had disappeared. The eggs are laid in
clusters between leaves, although in the laboratory they have also
been found between a piece of paper and a leaf. The number of eggs
in a cluster varies from 6 to 24.
The grubs, or larvae, are footless. Color of head, brown; body,
white, covered with rows of white hairs. There are four hairs on
the last segment of the abdomen. The larve soon fall to the ground
and feed on the roots of orange trees.
During 1908 this insect appeared in June during the blossoming
period and was seen scarring the fruit.
The green adult beetle is a ravenous feeder, eating the orange
leaves, especially the new growth.
The treatment is the same as for the orange-leaf weevil. Some
have made it a practice to pick off the weevils by hand and find it
more satisfactory than spraying, especially in small groves.
This is a large brown beetle which works at night, coming up from
its burrow at the base of the tree soon after dusk. The burrows are
from 4 to 6 inches deep and usually under the trees that the beetles
feed upon. The eggs are laid in these burrows and soon after they
are hatched the young grubs commence to feed upon the roots of the
The work of the beetles is more noticeable in young groves, espe-
cially where ground has been broken for the first time, as all the
plants on which they feed have been destroyed and there is nothing
but the orange left for them to eat.
The adult insects are often gathered by hand, men and boys being
employed for that purpose. Arsenate of lead is used as a spray for
these beetles, and it can be mixed with kerosene emulsion or with
The May beetle is a voracious leaf feeder. It generally appears
during April, May, and June, or a little earlier than the orange leaf
The "caculo,"1 or larva, of this insect is a large, white grub and
feeds on the roots of the orange, sugar cane, and a number of the
common grasses, causing a great deal of destruction. Often as many
as 50 grubs have been taken from around the base of a single young
When the caculos are present in great numbers, especially in newly
planted groves, they eat the small roots, and sometimes girdle the
taproots. In such cases the tree gradually turns yellow and dies
unless it is promptly treated.
Remove the soil from the base of the tree, take out the grubs, and
cut off any roots that are girdled; replace the earth and fertilize
heavily, so that the tree may have plenty of nourishment for a fresh
This pest is the variegated caterpillar of a butterfly belonging to
the genus Papilio, which makes its appearance during the summer.
It has been found in the larval stage at the station during July and
October. The caterpillars feed on the leaves of the orange, and if
present in great numbers will cause a great deal of damage, as they
are ravenous eaters. Hand picking is recommended where there are
but few insects. At the station very satisfactory results were ob-
tained by spraying the trees on which they were feeding with arsenate
of lead, 3 pounds to 50 gallons of water.
1 Caculo is the common name under which the grub of the May beetle is known in
: rto Rico.
FIG. 1.-ANTS' NEST AT BASE OF ORANGE TREE.
FIG. 2.-INJURY TO FRUIT DUE TO ANTS.
Bul. 10, Porto Rico Agr. Expt. Station.
INJURY TO FRUIT DUE TO WIND.
Ants are always found where the white fly and the Lecanium scale
are present. They attend these two insects to obtain the honeydew
secreted by them. When their supply of food is suddenly cut off, ants
often attack the young, tender shoots of the orange, eating them at
the point where they join the branches. They also eat young, tender
leaves, and a few cases have been observed where they had cut holes
in ripe fruit. Under these conditions much damage is done. They
also carry sand up around the base of the trees, and when there is
scant food supply they gnaw the bark of the tree where it is covered
by their sand houses. (P1. I, fig. 1.) Often when pineapples have
been removed from between rows of orange trees the ants attack the
latter in great numbers, scarring the trees, eating young, tender
shoots, and cutting holes in the fruit.
When they appear in this way they must be killed by spraying.
The simplest and most inexpensive spray that has been used is car-
bolic acid and soap. The formula for this emulsion will be found in
the section under Formulas." In spraying for ants it is advisable
to locate the nests and destroy the ants by spraying down into them.
A second spraying is always necessary the following day, as many of
the ants are away from their nests at the first spraying. In spray-
ing large nests it is a good plan first to spray a circle around the
nest and then to spray directly into it, thus making it impossible for
the ants to crawl out and insuring their being killed by the emulsion.
WOOLLY WHITE FLY.
This white fly, found in Porto Rico, is not the common citrus white
fly of Florida, although the latter has recently become established
there. It feeds upon the guava and orange, and has been determined
through the kindness of Dr. L. 0. Howard as Aleyrodes howardi.
It appears on the underside of the leaf and is usually attended by
ants, which feed upon the honeydew which it secretes. The eggs
look like little spots of dust on the underside of the leaf. In a short
time these develop into larvre, which spin white, silky mats. It is
during this stage that the ants attend them. Later the larva trans-
forms into a pupa, which develops into a tiny insect resembling a
It is recommended that a strong emulsion of kerosene be applied,
about one part of stock emulsion to six of water, a second application
following in about two weeks.
There exists on the island a little red spider which feeds upon the
essential oils of the orange. The leaves and fruit become rusty in
appearance when this oil is removed. The spiders prefer the under
or shady side of a fruit or leaf on which to feed, and for this reason
oranges sometimes become rusty on one side only. The eggs are laid
on the underside of the leaves, along the midrib. They are pinkish-
white in color and the empty eggshells resemble minute pearls. The
young are light yellow, later turning red. The adults can be readily
seen with a magnifying glass crawling over the, leaves.
The adult is readily held in check with sulphur sprays or with
any soap or kerosene spray which will kill soft-bodied insects. The
eggs are not so easily killed, and it is therefore advisable to spray a
second time two weeks later.
Sulphur may be applied dry by throwing it into the trees or by the
use of blowers. This should be done in the morning, when trees are
wet with dew, or immediately after a rain.
These insects are most prevalent during extended periods of
drought. During the rainy seasons they are held in check'by the
rain, as they are washed to the ground and destroyed. They were
first observed in the station grove in 1908.
During the spring of 1909 the rust mite was noticed for the first
time on the orange, grapefruit, and lemon. This mite closely re-
sembles the Florida species and probably is identical with it. It is
small, can not be seen with the naked eye, and it is only by careful
search with a strong glass that it can be found. Its habits are the
same as those of the red spider. The eggs of the rust mite are not
always laid on the underside of the leaves, but are often found on the
surface and on the fruit. They are silvery in appearance and, being
minute, are hard to distinguish from the oil cells. The leaves and
fruit of a tree infested with rust mites are of a dirty green color,
caused by the breaking down of the oil cells and the presence of the
cast-off skins of the insects, which are whitish.
The adult mite is of a lemon color; the head is three times as broad
as the body, there being a gradual tapering from the head backward.
The adult has two pairs of legs on the anterior portion. The rust
mite is not active like the red spider, it being very difficult to deter-
mine if they even change their position.
Treatment for the rust mite is the same as for the red spider.
The purple scale is present in all cultivated and wild groves of this
island, and is the most serious orange pest in Porto Rico. It appears
not only on the trunks and branches of the trees, but also on the
leaves and fruit. It is on the young branches and fruit that most
damage is done; the former are often killed and the latter so badly
spotted with scales that it has to be washed before shipment.
The life history is as follows: The eggs are very small, pearl white,
usually from 40 to 80 in number. The laying continues over a period
of 8 to 11 days; the first eggs hatch before the last are laid. Condi-
tions often so affect the hatching of the eggs that the hatching period
may extend to 16 or 18 days. Some eggs kept at the laboratory did
not hatch until the eighteenth day, whereas others hatched in 8 days
under the same conditions. This delay in hatching makes spraying
The young usually crawl from 12 to 24 hours before settling down;
after this they insert their sucking mouth parts into the epidermis of
the leaves and develop a covering consisting of white, waxy threads.
Under this coat or covering they remain for about two weeks, then
form a second covering; at the end of three weeks the male scales
can be distinguished from the females.
The adult male appears in five weeks and can be seen, with the aid
of a glass, crawling over the leaves and branches. At this period the
females are not full grown, as it takes seven weeks for them to de-
velop. At the end of this time they are often found with eggs. The
life cycle of the females requires from 8 to 9, and in some cases 10,
weeks. The adult male scale is much smaller than the adult female,
and both are reddish brown to dark purple in color. The adult fe-
male resembles a minute oyster shell. For this reason it is often
called the oyster-shell scale," but it should not be confused with the
oyster-shell scale of the North, as they are two distinct species.
The purple scale in the Tropics has no definite seasons for produc-
ing its young. At the station and in various groves of the island
crawling young have been found at all seasons of the year. On
account of its irregular appearance it is very difficult to eradicate
by spraying. The adult female scales and eggs are not killed by
any of the emulsions heretofore used by the planters. It is now
recommended that those who are using kerosene and crude-oil emul-
sions repeat their spraying in about 21 days; this leaves ample time
for the females which escape the first spraying to deposit their eggs
and for the young to hatch out.
These insects are generally found on the trunks and branches of old
trees. The infestation usually starts at the base of the trees and grad-
ually works up among the branches and often into the young twigs.
However, it very seldom spreads in this way on trees which have
been treated for the purple scale. The infestation is not so rapid
as with the purple scale, even though it is not attacked by as many
(or the same) fungi as prey upon the purple scale. There is, how-
ever, a black fungus that parasitizes the white scale, but in cultivated
groves this is rather slow in spreading. (P1. II, fig. 1.)
Life-history studies of this scale made at the station show that it
requires the same length of time to develop as does the purple scale.
The color of the male is white, with three parallel ridges extending
longitudinally. The female is reddish-brown in color and resembles
the purple scale in general appearance. The larve are yellowish-red
and when crushed leave a yellowish-red spot. The crawling young
are pinkish-red, and with a magnifying glass can be seen crawling
over the trunk and large branches of trees.
The most effective emulsions are kerosene with carbolic acid, 1 part
of the mixture to 5 of water, and crude oil with carbolic acid, 1 part
of the mixture to 15 or 18 of water. The directions for making these
emulsions will be found on page 28 of this bulletin.
In groves that have good windbreaks this scale is held in check
by fungi, and spraying is not necessary.
FLORIDA RED SCALE.
The Florida red scale is quite prevalent in the citrus groves and is
generally found on the leaves and fruit of the orange and lemon.
This insect does not spread as rapidly as the two scales previously
mentioned, but when found on the fruit it is very difficult to remove.
It develops in about eight or nine weeks. The crawling young are
yellow and settle down very soon after they come from under the
mother scale. Their first covering is of a slate color, which changes
in a few days to red. In about three weeks the sexes can be distin-
guished, and in five weeks the males are full grown and, with the aid
of a magnifying glass, can be seen crawling over the surface of the
leaves. At this period the females are not fully developed. The
young begin to come'forth in about 7 weeks and continue to appear
for from 9 to 11 days.
The adult male scale is much smaller than the female. It is round,
with a small flange on one side resembling a tiny red cap. The
FIG. 1.-BLACK FUNGUS ON WHITE SCALE (CHIONASPIS CITRI).
FIG. 2.-RED-HEADED FUNGUS (SPHAEROSTILBE COCCOPHILA) ON
female is red also. It is perfectly circular and without the flange.
The red-headed fungus (Sphcrostilbe coccophila) has been found
preying upon this scale.
Treatment for the red scale is the same as for the purple scale.
This insect, generally found on the small branches and leaves and
occasionally on the fruit, is attended by ants, which distribute the
young from place to place (PI. III, fig. 1). It attacks many of the
ornamental plants also, but is not considered a serious pest, as it is
readily held in check by one or two sprayings of kerosene emulsion.
This species is preyed upon during the rainy season by a white fun-
gus (Sporotrichum sp.) (P1. III, fig. 2). The adult is brown and
almost hemispherical, while the young is yellowish, flat, and ridged.
Several species of beneficial fungi have been found preying upon
the purple and white scales, namely, the red-headed, the white-headed,
and the black fungi.
The red-headed fungus (Spherostilbe coccophila) appears in the
Bayam6n district, and is more prevalent there than the white-headed
The white-headed fungus (Ophionectria coccicola) has been ob-
served in a great number of groves in the Pueblo Viejo district, where
it appears in greater numbers than the red-headed fungus. Both
these fungi prey upon the purple scale.
There are several species of black fungi that prey upon both the
purple and white scales. The species that prey upon the purple
scale spread very rapidly, whereas those that prey upon the white
scale spread very slowly.
The fungi should be carefully watched and may be taken as an
indication as to whether the grove is sufficiently protected by wind-
breaks. It must be remembered that fungi thrive only under moist
conditions, as the spores can not reproduce in exposed groves which
are constantly being dried and beaten by the winds.
METHODS OF INTRODUCING BENEFICIAL FUNGI.
In Florida, for the past few years, a great deal of attention has
been paid to the work of beneficial fungi. It has been demonstrated
that such fungi can be introduced into groves if they have a reason-
able amount of wind protection.
Porto Rico has the same beneficial fungi that occur in Florida, and
although the planters have never made special effort to introduce
them, there are certain groves in which the scale is held in check
thereby. The following methods for introducing fungi are taken
from Bulletin 94 of the Florida Station:
First method.-Select a tree which is thoroughly infested with scale and
tie a twig in it which has fruiting spores of the red-headed or the white-
headed fungus. The twig should be tied well up in the tree, but not so high
that the wind will dry out the fungus. If there is plenty of fungus three or
four twigs may be put in the tree so that the infection will be more rapid.
The rain and dew wash the spores down the trunk and branches which are
covered with scale and infect them. Fungi do not work as rapidly in young
trees as in old ones on account of the lack of moisture.
Second method.-By this method the leaves containing fungi are introduced
into trees which are infested with scale. The leaves should be tied or pinned
to the infested parts so that the rain and dew can distribute the spores.
Where plenty of material can be obtained it is better to use the first method,
as the twigs do not dry out as quickly as the leaves.
Third method.-This method consists of the introduction of trees which are
infected with beneficial fungi. The method is practical, but the infection is
not so rapid in the groves as when twigs are used in individual trees.
Fourth method.-Make a culture by placing a number of fruiting spores in
water and use as a spray for the scale-infested trees.
This spraying should not be done with a pump which has previously been
used for spraying Bordeaux mixture or lime sulphur, as these fungicides will
destroy the beneficial fungi. It is also well to use a pump which does not have
brass fittings; a galvanied-iron sprayer is best.
The black fungi which prey upon the purple and white scales can also be
introduced by tying branches containing them into trees infected by scale.
Three important questions must be considered when purchasing
land for planting: (1) Suitable soil; (2) shipping facilities; and
(3) protection from wind.
This last question is by no means the least important, owing to the
prevailing strong winds from the northeast. These winds are so con-
stant that it is almost impossible to start a grove unless it is protected.
If there are no natural windbreaks, artificial ones will have to be
Wind-swept groves can be easily distinguished from protected
ones. The trees in the former have a peculiar tired appearance; the
branches are blown to one side and covered with scale; the bark looks
dead and new growth becomes twisted out of shape, and in a few
months looks like the old.
As all fungi thrive only under moist conditions, the beneficial kinds,
therefore, never appear in these groves on account of the constant
action of the wind on the trees.
There are certain groves on the island which have been planted
for three years and even yet look as if they had just been set out.
Almost adjoining these groves are others, planted at the same time
FIG. 1.-HEMISPHERICAL SCALE (SASSETIA HEMISPHAERICA).
FIG. 2.-WHITE FUNGUS (SPOROTRICHUM SP.) ON HEMISPHERICAL
B~I 10 Pouo R o Agr Exp Sv n PLATE
FIG. 1.-PERMANENT WINDBREAK, TIMBER.
FIG. 2.-PERMANENT WINDBREAK, MANGO TREES.
Bul. 10, Porto Rico Agr Exp, Sta',ion
and in the same kind of soil, which look healthy and are producing
fruit. There is only one explanation for this difference and that is
that on one side of the road brush has been allowed to grow which
acted as a windbreak.
One of the best examples of the effect of a natural timber wind-
break is the Plantaje grove at Palo Seco. (P1. IV, fig. 1.) This
grove until 1908 did not need to be sprayed for the purple or white
scale. Since then some of the breaks have been taken out and the
scale has begun to come in.
Another grove near Manati shows the effects of wind protection
from the prevailing winds by hills, and spraying has not been neces-
sary for two years.
Many planters think that the first row of trees on the windward
side will soon protect the other trees, and give this as a reason for not
planting windbreaks. This is sometimes true, but a great deal of
time is lost in waiting for these trees to grow enough to afford pro-
There is not a grove on the island that does not need in some part
more protection from wind than it has at the present time. There are
always certain parts of the orchard which appear older than others,
though if the grower will examine his notes he will find that the trees
are all the same age and that there are windbreaks in localities where
the trees are more fully developed; furthermore, that not as much
spraying is required as in the unprotected parts.
There are two classes of windbreaks: Natural, such as hills and for-
ests, and artificial, such as bamboo, mango, brush, sugar cane, pigeon
peas, and bananas. There are two kinds of artificial windbreaks, the
permanent break and the temporary. Permanent breaks are set out
along the outer edges of groves for a permanent protection to them.
The temporary breaks are set out between the rows of trees and are
removed as soon as the trees afford protection for themselves.
Bamboo is one of the best quick-growing permanent windbreaks.
One year after planting it serves as a good protection for young trees.
It should be planted during the wet season, using cuttings about 2
feet long. Good results have been obtained by laying whole sticks in
a foot trench, burying them with 4 inches of earth and covering with
a little trash to keep the soil from drying out.
The mango is usually set out as a permanent break, but on account
of its slow growth it yields very little protection for the first three or
four years. (P1. IV, fig. 2.) In planting mangoes it is best to omit
at least one row of citrus trees and cut a deep ditch between them and
the mangoes, so that the roots of the latter will not extend into the
grove. It is advisable to head the mangoes low, so that it will act as
a break as soon as possible. Some varieties of Indian mangoes are
excellent and far superior to the native fruit. There is no fiber and
the turpentine taste is wholly absent.
Permanent windbreaks of native mangoes can be planted and
then inarched or topworked to the Indian. The best success has been
had at the station with inarching. Some of the 4-year-old inarches
are now bearing their first crop of fruit. If the mango is set out
and grafted, it not only affords a fine windbreak, but may become a
source of revenue.
In planting brush land in sections where the winds are strong it is
advisable to leave a strip of uncut timber 20 feet wide every 300 to
400 feet to act as natural windbreaks. The distance between the
strips should vary according to the land. When the land slopes
away from the wind the breaks should be farther apart.
Pigeon peas are used with success in young citrus groves as tem-
porary windbreaks. (PI. V, fig. 1.) This plant gathers nitrogen
and thus answers two purposes-acting as a windbreak and return-
ing nitrogen to the soil. The plant lasts about two years and then
dies. However, the old stocks may be cut back and new sprouts
allowed to come up. The trash made by the leaves and small branches
adds a great deal of humus to the soil. It is not as ravenous a feeder
as the banana.
Bananas are also usea as temporary breaks. (P1. V, fig. 2.) They
are very quick growing and afford excellent protection to young trees.
Sometimes they are a good investment, as the crops often pay for the
cultivation. There is one disadvantage in the banana as a windbreak.
It is a gross feeder, and if not watched sends its roots into the grove
and robs the young trees of their nourishment, and unless they are
very heavily fertilized their growth will be retarded after the first
year and a half. This may be overcome by heavy application of
fertilizers or by plowing a deep furrow along the row of bananas,
thus cutting the roots so that they will not extend into the grove.
Temporary windbreaks should not be removed from young groves
all at once. It is best to remove them gradually, especially those of
banana and pigeon pea. Alternate rows should be removed, leaving
some protection, especially when the permanent break is not suffi-
ciently large to protect the whole grove. When it is found that some
areas still need protection, they should be left with a windbreak, even
if the uniform appearance of the grove is marred. The trees thus
protected will soon attain the size of the other trees.
Insects are not wholly to blame for all disfigured and discolored
fruit. The constant chafing of a young orange, when a week or two
old, against a leaf will produce a scar in the mature fruit; scars are
also produced by the fruit hitting thorns. Many fruits, especially
Bul. 10, Porto Rico Agr. Expt Station.
FIG. 1.-TEMPORARY WINDBREAKS, PIGEON PEAS AND SUGAR CANE.
FIG. 2.-TEMPORARY WINDBREAKS, BANANAS AND PIGEON PEAS.
those on the lower branches, are injured by animals or by cultivators,
as it takes only a very slight knock to bruise a young orange.
A number of observations were made of scars caused by the chafing
of the wind, and it was found that there was a marked difference in
the amount of scarring on the two opposite sides of the tree. In one
case the windy side showed 23 scarred to 234 unscarred fruits, while
the lee side of the same tree showed 7 scarred to 210 unscarred. This
scarring was caused by the constant rubbing of the fruit against
leaves or small branches. The scars appeared on the very young
fruit and looked dark, more like a bruise. As the fruit ripened the
bruise hardened, lost its green color, and appeared silvery. (P1. I,
The scars made by ants are altogether different from those pro-
duced by the wind, the former being deep-seated and caused by the
insects removing some of the epidermis and eating into the fruit.
(P1. I, fig. 2.)
There are several species of ants which feed upon the nectar
secreted by the orange blossoms. The brown ant and the little black
ant are especially fond of the nectar. These two species have been
seen working in the blossoms in the early morning, sipping the nectar,
and toward noon, when it has been exhausted, attacking the unopened
blossoms, or young fruit. Some cases have been observed where the
green calyx leaves were eaten so badly that the fruit dropped. In
other cases the pistil was chewed off and the fruit never developed.
Again, the brown ant sometimes cuts holes in the young fruit.
Ants do more damage during years when there is a scanty bloom or
when the bloom extends'over a prolonged period, as they eat the
fruit when not supplied with sufficient nectar.
Scars made by the small orange-leaf weevil are of the same char-
acter as those made by the ants, only they are much larger.
Mites and spiders produce discolored fruit. They pierce the oil
cells with their beaks and remove the oil, causing the fruit to turn to
a brown or russet color.
Fruit rust is also caused by a fungus which destroys the oil cells.
During the bloom of February, 1909, it was found in one grove that
from 13 to 45 per cent of the young fruit which had just formed
was scarred by ants and other insects. A few experiments were car-
ried on to see whether this scarring could be stopped by spraying.
Kerosene emulsion made with crude carbolic acid, 1 part to 17 parts
of water, was applied to trees in full bloom; the spray was forced
down into the blossoms. Four days later the new fruit which had
just formed was examined and showed only 5 per cent scarred, while
fruit taken from the check rows adjoining showed from 45 to 55 per
The second lot of scars was caused by sucking insects and ap-
peared as if a sharp pin had been drawn across the fruit. The skin
was broken and the oil cells were destroyed. The scars were prob-
ably caused by thrips, which were present in these trees in great
NOTES ON SPRAYING.
Spraying not well done is but little better than no spraying at all.
Every part of the tree must be covered with the emulsion, as the
parts left untouched become sources of immediate infection. In
spraying for scale, for example, it is not the amount of emulsion used
that does the work, but the emulsion that actually covers the scale
and penetrates its covering.
Trees can be sprayed more easily and much better work can be
done immediately after pruning, as the operator of the nozzle can
hold the extension rod into the center of the tree and direct the spray
outward and at the same time cover the underside of the leaves. If
the trees are headed low and the centers are well opened not so much
of the emulsion is wasted, and the work can be done more quickly
In spraying trees it is best to commence at the base and work up,
spraying the underside of the branches and leaves first, gradually
working toward the top. If the trees are not too large with open
centers, and the operator has a long extension with a one-fourth
elbow connection for the nozzle, all the spraying may be done from
one side of the tree. The one-fourth elbow is very useful in' this
work, as it not only enables the operator to reach the underside of the
trees, but also to spray the tops by raising the rod above the tree,
thus directing the spray downward without adjusting the nozzle.
Pains should be taken to cover every spot, especially the underside of
every leaf, as many of the insects are found there.
Where strong oil emulsions are used it is recommended to hill up
the earth around the trees previous to spraying, and afterwards to
clear the earth away so that the oil will not remain around the trunk
and soak down to the roots. In sandy soils the earth may be thrown
up quickly by the operator immediately preceding spraying, but
where the soil is firm a man or boy should precede the sprayer to do
this, as it will save time. The soil should be removed as soon as the
spray stops running down around the base of the tree.
COVERING FOR OPERATORS.
Operators of sprayers need something to protect their clothing,
as it is impossible to spray trees against the wind without getting
wet, and furthermore, it is not likely that the work will be done
thoroughly under such conditions. The spraying apparatus should,
therefore, be provided with a long extension rod which permits the
operator to stand at one side and direct the spray into the tree. He
can also protect himself with a coat made by cutting three holes into
some light-weight cloth, such as flour sacking or gunny cloth from
sacks, which answers the arpose -very well.
Sprayers are divided into two classes, hand and power sprayers.
At the present time there is only one power sprayer on the island,
all work being done by barrel and knapsack pumps. The most com-
mon sprayer in use is the barrel pump, mounted on a two-wheel cart
and drawn by hand or by a mule. Barrel pumps are more satis-
factory when fitted with extension rods and two hose each from 25
to 30 feet long. Much time and labor are saved by using long hose,
as it is much easier to draw a line of hose around a tree than it is
to haul a spray cart around it; and as spraying has to be suspended
while moving the cart, much time is lost. A two-wheel cart drawn
by a mule is a good arrangement for orange spraying, as it does not
take up much room and the driver does the pumping.
The knapsack and small compressed-air pumps are very useful in
spraying trees for ants or pineapples for mealy bugs; also for use in
gardens and on trees up to the age of 1 years. As the trees become
larger they require a greater amount of emulsion to wet them thor-
oughly and a great deal of time is consumed in filling a knapsack or
small compressed-air pump, therefore a barrel pump at this stage is
Extension rods and hose attachments are also a great addition to
hand pumps. One objection to the small compressed-air pump is the
lack of an agitator, and under these conditions the ingredients of the
spray are liable to separate from each other; this is especially true in
using emulsions which contain arsenate of lead.
Power sprayers are classed according to the kind of power used in
running the pumps, such as gasoline, steam, compressed-air, and
Geared sprayers are those which receive their power from a series
of gears and chains -which connect the pump with the running gear
of the wagon. These sprayers are used for garden truck, cotton,
grain, and grapes, where the wagon can move along continuously.
This arrangement is not as satisfactory for spraying in orange groves,
as the trees are planted so close together that sufficient power would
not be generated by passing from one tree to the next. It might be
possible to obtain sufficient power to spray alternate trees, but as all
spraying in Porto Rico is done with trees in foliage, it requires much
more liquid than for trees of the same size which have shed the
Of the various power sprayers on the market the gasoline engine
type appears to be most practical, especially for spraying fruit trees.
Every pump should be supplied with a good, strong agitator to
give the best results.
There are two classes of agitators for barrel pumps; the most satis-
factory kind is the one which consists of two paddles attached to an
iron rod, which is connected with the pump handle; thus at every
stroke of the pump the paddles are in action keeping the emulsion
The best agitators for power sprayers are of the rotary type.
They are made in the form of a propeller and connected with the
engine. As soon as the engine is started the emulsion is being thor-
oughly mixed. Dasher agitators are not as satisfactory as the pro-
peller type. They are more liable to give out, as there is a jerking
motion caused by their imperfect connections with the engine.
Extension rods enable the sprayer to do much better work. They
are generally used on barrel sprayers and power outfits, but are also
practical when used with knapsack or bucket pumps.
The length of the extension rods to be used should vary according
to the kind of spraying to be done. Bucket and knapsack pumps for
spraying young trees 5 to 6 feet high should be fitted with extension
rods 3 feet long. Barrel pumps should be equipped with extension
rods and the length should depend upon the size of the trees to be
sprayed. For trees 10 to 12 feet high use a 6 to 8 foot extension rod,
while trees larger than this should be sprayed with a 10-foot rod.
Extension rods made of one-fourth inch brass tubing covered with
bamboo are very light and not cumbersome. All rods should be sup-
plied with stopcocks, which enable the sprayer to shut off the stream
and examine his work. Homemade extension rods can be made with
a piece of one-fqurth inch pipe threaded at both ends so that one end
will fit the stopcock and the other the nozzle.
For very large trees spraying towers are recommended. These are
often built on top of a tank wagon. They are usually supplied with
power outfits and are made in sections, so that they may be removed
when not in use.
There are two general types of nozzles, the Bordeaux nozzle, which
produces a fan-shaped spray, and the Vermorel, which produces a
conical spray that breaks up into mist. The spray from a Bordeaux
nozzle carries much farther than the Vermorel before breaking up.
Both types are used on the island, but the Vermorel is used almost
exclusively for spraying with oil emulsions. The fine mist produced
by this nozzle is preferred when using oil, as it takes only a small
amount of it to cover the insects. In the form of a fine mist the
emulsion is more evenly distributed.
Vermorel nozzles are made in two sizes; the small size is made with
disgorgers whereas the large size is made without them. The large
nozzles are more suitable for barrel pumps and power sprayers, and
the smaller ones for knapsack pumps. In spraying small trees the
small nozzle is more satisfactory, as little emulsion is lost. Large
nozzles should be used only where there is sufficient power in the
pump to produce a fine mist.
Drench spraying is not as satisfactory as mist spraying, as a great
deal of the solution is lost.
INSECTICIDES AND FUNGICIDES.
INSECTICIDES FOR BITING INSECTS.
Paris green can not be used as effectively here as in the United
States, on account of the heavy tropical showers which occur nearly
every day during the rainy season. In some of the drier parts of the
island this insecticide with air-slaked lime can be used with good
results as a dust spray.
ARSENATE OF LEAD.
Arsenate of lead has been introduced, and at the present time it is
taking the place of Paris green; it is not readily washed off by the
rains, and it can also be used without any danger of burning the
foliage. The formula is as follows:
Arsenate of soda (50 per cent strength) ------ounces- 4
Acetate of lead------------------------------do-- 11
Dissolve the arsenate of soda in 2 quarts of water and the acetate of lead
in 4 quarts of water, using wooden vessels. Pour the solutions together and
add 10 to 50 gallons of water. The white precipitate formed is arsenate of
lead, which remains in very fine particles and is held in suspension much longer
than Paris green. It can also be used with Bordeaux mixture or with kero-
ARSENITE OF LIME.
Formula for preparing white arsenite of lime is as follows:
White arsenic ------------------------ --pound 1
Crystal sal soda ------------------------------- do 4
Water ----- ------- -------- gallon- 1
SU. S. Dept. Agr., Farmers' Bul. 127 (rev. Pd. 1908).
Mr. Marlatt says:
Place the above ingredients in an iron vessel, which is to be kept exclusively
for this purpose, and boil for 20 minutes or until dissolved. To 40 or 50 gallons
of water a pint of this stock solution and 3 to 4 pounds of freshly slaked ikue
are added. This excess of lime not only takes up any free arsenic but by Atp
distribution on the foliage enables one to determine how well the spraying has
been done. This formula has been thoroughly tested and used now for many
years, and is fully as efficient as any other arsenical and far cheaper. ChemiC-
ally it4s arsenite of lime. The soda is used to hasten the process and to insure
the combination of all the arsenic with the lime. The greatest care should bI
exercised in preparing the stock mixture, and afterwards it should be plainly
labeled to prevent its being mistaken for some other substance. The only objec-
tion to its use is the necessity of handling the poisons in its home preparation.
INSECTICIDES FOR SUCKING INSECTS.
A great number of contact poisons are being used in the island for
destroying the various scale insects. Among the most promising are
the miscible oils, crude petroleum, kerosene emulsion, and lime-sul-
Many of the best emulsions have been condemned because they were
not made exactly according to the formula. This has been especially
true of the crude petroleum and kerosene emulsions. Not enough
attention has been paid to the making of these emulsions. Often in
ordering the ingredients the specifications are not clear, and as a con-
sequence the goods that arrived are not just what was desired. Im-
perfect emulsions, in which the oil separates again from the water
after being diluted, result from the use of hard water and from
shortening the time required in mixing. Rain water should be used
in making emulsions.
Miscible oils are concentrated solutions of ingredients which have
insecticidal properties to which it is simply necessary to add water
to form the emulsion. They are usually handled commercially and
have become one of the most promising scale destroyers. A manu-
factured miscible oil is used by some of the fruit growers with good
results, having proved itself to be one of the best scale remedies that
has yet been tried. The large growers can not use it, however, as it is
too expensive. Tests made here show that a strength of 1 to 25 not
only destroys all the crawling young and those bearing the first cov-
ering, but also a great number of females with eggs. This emulsion
has been used with good results on orange and grapefruit. At a
strength of 1 to 20 some leaves dropped, but these were incrusted
with scale or from badly infested branches. Homemade miscible
oils were experimented with during 1908 and a number of formulas
have been tried. The most promising are those made with crude
petroleum and rosin oil. These give very stable emulsions and their
destructive power is very high.
WMiscible oils have many advantages over the kerosene and crude-
oil emulsions. After the soap is once made no more heat is required
to make the stock emulsion or the various dilutions of the stock
emulsion. Only one-third of the soap is heated and the other two-
thirds is made up of kerosene and water. The time required for
making the soap is about an hour.
If properly made they should not have any free oil on the surface
when mixed with water. Erlsions made with kerosene do not re-
quire as much attention as those made with the heavier oils, such as
rosin, paraffin, or crude oil.
On April 21, 1908, a number of experiments were made with the
formula recommended in Bulletin 79 of the Delaware Agricultural
Experiment Station. The trees were incrusted with scale at that
time, but by March, 1909, they were absolutely free from scale. The
scale did not immediately drop, but the trees have been cleaned by
the rains and do not appear as if they would need .spraying during
the coming season. No ill effects from these sprayings can be seen.
The trees have had their usual amount of new growth and blossoms.
There is always a small percentage of leaves that drop, but they are
usually the ones which have been covered with scale and have become
weakened by the constant action of it. The loss of such leaves is not
detrimental, as it is better that they be removed. Healthy, vigorous
leaves are not injured. Similar results have been obtained with
paraffin and crude oils.
These sprays should be applied with a nozzle that gives a very fine
mist. The oils are very penetrating, and for this reason a smaller
amount of emulsion is needed than of the old kerosene emulsion
Before the stock emulsion is taken from the barrel the whole
mixture must be thoroughly stirred, as the oils are liable to separate
For stirring the emulsion a piece of board about 4 feet long and
4 inches wide, to the base of which has been nailed a strip of board
10 inches long by 4 inches wide, has been found convenient. By using
such a paddle the emulsion at the bottom of the barrel, which is
thicker than that at the top, is raised and the whole mass becomes
uniform. It is always advisable to test the stock emulsion before
taking any out for spraying. If any free oil is found, add a little
water and after thoroughly stirring test it again. Continue this until
a perfect emulsion is obtained. If this testing is not done, an emul-
sion with free oil is liable to be sprayed upon the trees, which will
kill some of them. These emulsions are rather stable, and after one
has determined the amount of water necessary to make a complete
emulsion it very seldom varies. Where spraying is being done on an
extensive scale the stock emulsion may be placed in the bottom of the
spray tank and the water slowly added, stirring the whole until about
half of the amount of water has been added, then the rest of the
water may be added and the spraying begun.
The dilutions of all formulas have had to be changed, as all spray-
ing in Porto Rico is done on trees with foliage. The dilution of
crude oil formula set forth in Bulletin 49 of the Connecticut Storrs
Agricultural Experiment Station was ganged from 1 to 15 to 1 to 25,
the latter strength having exceptional killing powers. It not only
kills the young purple scale, but also the females with eggs.
The same can be said of emulsions in which paraffin and kerosene
oil are substituted for the crude oil. The miscible emulsions made
with heavier oils do not evaporate as quickly as those made with
lighter oils, and for this reason their killing power is extended over
a longer period. It has often been observed that the old scales seem
to retain a certain amount of oil which is later on set free by the
rains. This seems to be sufficiently strong to kill any crawling young
whose mother has escaped being killed. The oil particles of these
emulsions made with kerosene were so finely divided that they could
not be seen with low powers of a compound microscope.
All the work done with these emulsions has been on young-trees
which were not fruiting. They will be tested on trees with fruit to
determine whether they cause the young furit to drop or whether
they produce any discoloration.
Directions for making miscible oils.-There are three steps to be
taken in making miscible oil emulsions before the emulsion for spray-
ing is obtained. First, the cooking of the soap and the adding of
the kerosene and water. Second, making the stock emulsion out of
the soap solution and various oils. Third, diluting the stock emul-
sion for spraying.
The soap solution should be made in the open air or under an open
shed, as the mixture is inflammable when it reaches 3000 F. It is
also advisable to make the soap solution in a receptacle that is large
enough to allow plenty of room for boiling. When the soap reaches
2400 F. it begins to boil and continues to boil very violently until it
reaches about 2800 F. During this time the mixture foams and in-
creases to at least double its volume. It is, therefore, very necessary
that the receptacle be sufficiently large. When the soap reaches 3000
F. it should be removed from the fire and the kerosene and water
added. First, pour the kerosene in slowly, thoroughly stirring the
mixture; allow this to cool a little, then add the water. It is better
to let it cool until the soap plus the kerosene is below 2120 F. The
following formula is used in making the soap solution: 1
Menhaden oil --------------------- gallons-- 10
Carbolic acid ---- ----------------- do--. 8
Caustic potash __- _.----- ------pounds- 15
Heat to 3000 F., and then add:
Kerosene ----------------------------- gallons--_ 14
Water ------------------------------------ do-- 22
In making the soap it is well to have the kettle covered with boards
with a hole in the center through which a thermometer can be placed to
take the readings. It does no harm if the soap reaches 310 or 3150 F.,
but it is not safe to continue the boiling after the soap has reached
3000 F., as it is more liable to take fire. After the soap solution is
completed the fire can be drawn and the mixture placed in a barrel,
after which the kerosene and water are added. The soap should be
slightly ropy, but should run readily and not separate upon standing.
A half barrel of this soap has been left standing for six months with-
out undergoing any change.
Stock emulsions are made by the following formula:2
Soap solution-------------------- -----gallons 8
Crude oil --------------------- ------ ------ do 18
Rosin oil ------ --------------------- do- 4
Water -------------------- ------- --------- --do.- 3
Or more if needed.
This formula does not state definitely the quantity of water neces-
sary to obtain an emulsion free from oil, as the amount to be used
often varies. After the stock emulsion has been thoroughly mixed
try a few drops in a glass of water, and if no oil appears the emulsion
is ready to be diluted with the water for spraying. It is recom-
mended to use 1 gallon of the stock emulsion to 25 gallons of water
for trees without fruit.
KEROSENE AND CRUDE-OIL EMULSIONS.
Kerosene emulsion was one of the first sprays to be used by the
fruit growers on the island. The results from one spraying with a
solution 1 to 5 parts of water have not been satisfactory, only the
crawling young and those bearing the first covering being killed.
Crude oils have given better results. This oil does not evaporate
as readily as the refined or lighter oils, therefore remaining on the
trees for a longer period and killing more scale. A smaller per-
centage of oil is required in the crude-oil formula. These emulsions
break down more quickly than the kerosene emulsions, and for this
SDelaware Sta. Bul. 79.
2 Connecticut (Storrs) Sta. Bul. 49. Modified by increasing the amount of water used.
reason are not used to so great an extent. It has been shown by
experiments that the destructive power of crude-oil emulsion, 1 to 15
or 18 parts of water, is equal to that of kerosene emulsion 1 to 5.
While the price of these two oils is the same, the kerosene makes a
more expensive emulsion than the crude oil, as it is not so highly
diluted, this difference in the cost of the two emulsions being about
1 cent per gallon.
Kerosene emulsion made with whale-oil soap is one of the oldest
insecticides in use. It is not as difficult to make as the crude and
miscible oil emulsions. It is not, however, as effective in controlling
scale, but as it is easily made and does not separate it is still used
by many fruit growers. The formula is as follows:
Kerosene ------------------ gallons-_ 2
Water -------do--.. 1
Whale-oil soap-- --------------------------- ounces-. 8
Put the kerosene oil in a spray pump. Dissolve the soap in the water by
boiling and pour the solution' into the oil; mix the whole by pumping for about
10 minutes, directing the stream back into the pump. If a large quantity of
the emulsion is being made, it should be pumped longer. A creamy mixture
should be obtained, which will hold up from two to three weeks.
KEROSENE AND CRUDE-OIL EMULSIONS WITH CRUDE CARBOLIC ACID.
During 1908 crude carbolic acid was used in combination with both
crude-oil and kerosene emulsions. These emulsions were tested micro-
scopically and appeared very different from the emulsions made
without the crude carbolic acid. The oil particles are more finely
divided, in some cases their diameter being only one-third to one-
fourth the size of those in emulsions made without the carbolic acid.
The killing power of these emulsions is greater than those made
without carbolic acid, and'they are more stable. Very little, if any,
free oil could be found, even after the emulsion was allowed to stand
It seems quite possible that the carbolic acid will prove beneficial
as a fungicide, but not to such an extent as the sulphur in the lime-
sulphur mixture. Crude carbolic acid varies greatly in strength.
The formula for kerosene emulsion containing crude carbolic acid,
100 per cent (dark), is as follows:
Kerosene ------------- --------------- gallons- 2
Water -------------------------------------------do 1
Whale-oil soap (hard) ---------------------------pound__
Whale-oil soap (soft)--------------------- quart- 1
Crude carbolic acid, 100 per cent (dark) --------------pint-- 1
This emulsion should be made the same as kerosene emulsion. The
carbolic acid is emulsified in the hot water with the soap.
Crude carbolic acid has been used in the various crude-oil sprays
for ants, and the tests show that the amount of free oil which usually
appears on these emulsions is practically eliminated.
CRUDE-PETROLEUM EMULSION WITH SAL SODA.
This formula has been used on trees which were infested with
purple and white scales and sooty mold.
Crude petroleum ______________gallons- 5
Water ---------------------- ------ do-- 5 5
Whale-oil soap -- -- ------ pounds- 2j
Sal soda -------------------- ----------------do 2
Place the oil in a barrel. Dissolve the soap and sal soda in boiling water.
Mix the two by pumping back into the barrel for 15 to 20 minutes. Stock
emulsions made according to this formula have given satisfactory results. Use
1 part stock solution to 15 parts of water.
Lime sulphur is one of the few simple sprays which we have that
has insecticidal and fungicidal properties, and for this reason it is
becoming more and more popular. The only objectionable feature
is the boiling, which takes from 40 to 60 minutes. The formula is as
Fresh lime ------- -- --------------- pounds- 20
Flowers of sulphur _----- ------_----- -- do ..- 15
Water ----------------------------------- gallons 60
Place thfe sulphur in an iron kettle and add 1 or 2 gallons of water, mak-
ing the whole into a thick paste; heat, and when the mixture reaches the boil-
ing point add the lime. Sufficient water must be added from time to time to
slake the lime, after which the mixture is left to boil until it becomes a dark
olive green; this generally takes from 40 to 60 minutes. After the mixture has
been thoroughly boiled, sufficient water is added to make 1 gallons, then it
is strained and the remaining 45 gallons of water are added. This water does
not need to be heated, as the boiled portion of the spray contains sufficient heat
to keep the mixture warm while it is being put on the trees. It should be
applied warm, although good results have been obtained with cold lime-sulphur
spray. In making large quantities of this mixture steam should be used for
Lime-sulphur spray was applied to two rows of orange, grapefruit,
and lemon trees in the experimental grove to compare the result with
that from other sprays. This spray was made of 20 pounds of un-
slaked lime, 15 pounds sulphur, and 60 gallons water. All the crawl-
ing young scale and full-grown male scale and also a high percentage
of females with eggs were found dead. This spraying was done on
January 16, 1907, and eight days later no crawling young were found.
The results with lime sulphur are not equal to those obtained with
the miscible oils made with kerosene, paraffin, or crude oil, but they
are far superior to the results obtained with the kerosene emulsion.
The cost of the lime-sulphur wash is about the same as that of misci-
ble oils 1 to 20, but as it is advisable to use the oil 1 to 25, or in some
cases 1 to 30, it makes the cost of the latter less than that of lime
Lime sulphur is not only a good insecticide, but it also has fungi-
cidal properties. In groves where lime sulphur has been used there
is practically no scale and very little rusty fruit. While this spray
was used for the purple scale, it also held the rust mite in check.
Great care should be taken in applying a fungicide unless it con-
tains some insecticidal properties. The various scales are preyed
upon by beneficial fungi, which are sure to be killed by the fungi-
cides; therefore it is recommended to apply an insecticide before or
just after using a fungicide, so that the scale will not get too vigor-
ous a start and injure the fruit; or it is still more practical to apply
a spray which is in itself a fungicide and an insecticide. Lime sul-
phur seems to meet these two qualifications. This spray has at least
two advantages over the oil emulsions; it remains on the trees and
fruit for three to four months and during this time seems to retain
some of its beneficial properties. When it dries it is white, and
thus one can readily see what part of the tree has been left un-
The fungicidal properties of lime sulphur do not remain on the
trees as long as Bordeaux mixture. This has been observed in a
grove where Bordeaux mixture was used, and the beneficial fungi
did not begin to control the scale until after the first year. Lime
sulphur was applied in the same grove, and at the end of six months
beneficial fungi had established themselves and were checking the
work of the scale.
CAUSTIC SODA AND SULPHUR WASH.
The following formula has been used extensively for red-spider
and rust mite in Florida:'
Flowers of sulphur --------------------pounds 20
Caustic soda, 98 per cent----------------------- do.--- 10
Water -------------------------- -------gallons 20
For spraying use 2 gallons stock emulsion to 50 gallons of water.
This strength kills the mite and spider, but not their eggs. Sulphur
may be added to kerosene and crue-oil emulsions as a remedy for
mite and red spider.
U. S. Dept. Agr., Farmers' Bul. No. 127 (rev. ed.).
FORMULA FOR EMULSION FOR ANTS.
Although the ant is a biting insect, very unsatisfactory results
have been obtained by the use of stomach poisons, as ants will only
eat the bait for a little while. By the use of contact poisons ants
can, however, be combated. The following formula has been used
with great success:
Water ------- ---------quart__ 1
Soap (Good's caustic potash or whale-oil soap or Fairbank's
blue cloud soap) ------------- ---------pound-_ j
Crude carbolic acid, 100 per cent (dark) ----------- pint-_ 1
Dissolve the soap in water and add the crude carbolic acid, then add suffi-
cient water to make 2 quarts. This should be used as a stock solution, using
1 pint of the stock to 6 gallons of water.
Bordeaux mixture is used in combination with arsenate of lead.
In this way two sprays are applied at once-a stomach poison and a
fungicide. This is far more.economical and fully as good results are
obtained as when the two sprays are used separately. The formula
for Bordeaux mixture is as follows:
Copper sulphate --- -----------------pounds- 4
Quicklime -------------------------------- do-_ 0
Water --------- _________gallons 50
Dissolve the copper sulphate in 25 gallons of water. This is very easily done
by putting the copper sulphate in a bag which is suspended by a rope in a
barrel; this enables one to determine if all the sulphate is dissolved. Slake
the lime in a small amount of water, then add sufficient water to make 25
gallons. The two ingredients, copper sulphate and lime, may be used as a
stock solution. For making Bordeaux, use equal parts of the two, pouring them
into the spray tank at the same time.
Wooden vessels should be used for the mixing of the above, as
Bordeaux mixture corrodes iron.
Stock solutions of Bordeaux mixture may be made by slaking 50
pounds of lime in a barrel and adding sufficient water to make 25
gallons, then for each barrel of spray use 3 gallons of the lime
mixture. In the same way dissolve 50 pounds copper sulphate in
25 gallons of water and use for each barrel of Bordeaux 2 gallons
of this solution. To obtain the best results each of these solutions
should be prepared separately with 25 gallons of water and then
In spraying with Bordeaux mixture a pump with a good agitator
is necessary, as the precipitate, which is a chemical union of the lime
and copper, has a tendency to settle. All parts of the pump should
be made of brass, not iron.
HINTS ON PURCHASE OF INGREDIENTS.
Extreme care should be used in purchasing the ingredients for the
soap and for the stock emulsions. There are a number of different
grades of the various ingredients on the market, but from experi-
ence at this station and in the United States it is best to obtain the
ingredients direct from large dealers and according to exact speci-
fications. The following specifications and prices are quoted by
New York firms:
Pure menhaden, or fish oil, in barrel lots costs from 30 to 37 cents
Caustic potash, 92 per cent, ground, can be purchased at 8 to 9
cents per pound by the hundredweight.
There are a number of grades of carbolic acid on the market which
range from 20 to 100 per cent. The lower grades are not suitable for
making the soap as they have a tendency to produce thick soaps,
which do not emulsify the oils. The high-grade 100 per cent crude
carbolic acid, of straw color, can be obtained for 40 to 45 cents per
gallon in barrel lots. A 100 per cent crude carbolic acid, dark, has
also been obtained, which has given equally good results. This costs
a few cents less per gallon than the straw color.
Rosin oil is a vegetable oil obtained from the turpentine distilleries
and costs from 23 to 26 cents per gallon in barrel lots.
The present condition of the citrus industry in Porto Rico is very
promising. No insects are found in the groves that can not be held
in check by thorough treatment.
For biting insects, arsenate of lead is the best spray for the condi-
tions that exist on the island. Paris green does not have the adhesive
power of the arsenate of lead.
Sprays containing oils are used for scale insects, but they will also
keep the rust mite and red spider in check. However, where spray-
ing is being done for the rust mite and red spider alone, it would be
better to use sulphur sprays.
The purple scale has been the worst enemy, but since windbreaks
have been introduced the beneficial fungi play a very important part
in checking it
The hemispherical scale and the Florida red scale are both held in
check by the sprays used for the purple and white scales, and so is
the white fly. It is very seldom that these insects need special treat-
It is considered advisable to pick all the fruit before the new blos-
som growth starts, so that the sprayers may clean the trees well for
the new crop. If the trees are thoroughly cleaned in this way, there
is very little chance for the fruit to become scaly.
A great deal of the cultivated fruit has been disfigured either by
fungi, mechanical bruises, or by insects. Special attention is called
to the last two causes of disfigured fruit. The insects causing tdw
worst scars on fruit are the ants, small orange-leaf weevil, rust mitt
and red spiders. The two last mentioned rust the fruit.
All these insects, however, are held in check by sprays describeddAw
Mechanical injuries are caused by the fruit rubbing or hitting
against some foreign object, as the leaves or branches.
Of the various oil emulsions which have been introduced the most
promising are the miscible oils and the crude-petroleum and kerosene
emulsions, the last two being made with crude carbolic acid, 100 per
At the present time miscible oils are recommended only for trees
which have not come into bearing. No test has been made on trees
with fruit. It may be possible to use these emulsions on trees with
fruit by changing the formula, but when this is done a second and
perhaps a third spraying will be necessary, as the highly diluted spray
kills only the young.
In purchasing materials for homemade miscible oils great care
should be exercised to obtain the exact ingredients called for in this
bulletin. Homemade miscible oils will not be practical for small
planters, as the ingredients in small lots are more expensive. They
may be purchased, however, by an association, or a number of small
planters may club together to purchase them.
For trees without fruit it is recommended that the small planters
use kerosene or crude-oil emulsions made with 100 per cent crude car-
bolic acid (either straw colored or dark) ; use 1 to 5 for kerosene emul-
sion and 1 to 16 or 18 parts of water for crude oil for the purple and
white scales, and repeat spraying in three weeks.
For trees in fruit use kerosene or crude-oil emulsions made with 100
per cent crude carbolic acid (either straw colored or dark); dilute
them 1 to 8 or 1 to 25 parts of water, respectively, repeating the spray-
ing every two weeks for four or five times.
Kerosene and crude-oil emulsions are greatly improved by the
addition of a small amount of crude carbolic acid. When carbolic
acid is used the oil particles are more finely divided and the emulsions
are more uniform. This is especially true of crude-oil emulsion.
Emulsions made with sal soda are especially adapted to groves
having an abundance of sooty mold. This fungus accompanies the
Lecanium scale and the white fly.
Lime sulphur wash is the best combination fungicide and insecti-
cide. As an insecticide it is very valuable in combating the purple
scale, red spider, and rust mite, and as a fungicide it is used for scab.
Great care should be exercised inapplying fungicides, as they kill
all the beneficial fungi which prey upon the various scales. At times
fungicides have to be applied, but before using them the scale should
be well under control; if not, an insecticide should be used imme-
diately after the fungicide.
TIME OF SPRAYING.
Spraying conditions in Porto Rico are very different from those
in the United States. Many insects have no" definite season of ap-
pearance. This is especially true of the scale insects. The constant
appearing of the young makes the work of spraying more difficult.
It is only by careful study and constant observation that one learns
to recognize the condition of trees and is able to determine at what
time spraying is necessary.
Sometimes it is necessary to spray a crop of nearly mature fruit;
this complicates matters, as a much weaker solution will have to be
used than for trees without fruit.
There is no distinct blossoming season of the orange over the
island, and the same may be said of the trees in individual groves.
Some years there is a very scattering bloom, some trees being in full
bloom, while others have not begun to show the blossom growth.
The same trees will bloom one year in February and the next year in
May or June. There are generally two periods of blooming, one in
January and one in July.
The rainy and dry seasons occur at different times in different parts
of the island. The Mayaguez district may be having its dry season
while the Rio Piedras and Pueblo Viejo districts are having their
These varying conditions make it impossible to give hard and fast
rules regarding the time of spraying.
When the fruit is the size of a pea almost any spray will injure
the crop; thus spraying should be deferred until the fruit has reached
the size of a walnut, as the fruits are then less liable to be injured by
emulsions. A weak emulsion of kerosene, 1 to 8 or 9, or crude oil,
1 to 25, should be used. As these are weak sprays, at least three to
five sprayings will have to be given at intervals of two weeks in order
to kill all the insects.
Windbreaks (Pls. IV and V) are as essential to a grove as a break-
water is to an open harbor. In groves which are thoroughly pro-
tected little, if any, spraying is needed for the purple and white
scales, as the beneficial fungi, which thrive under moist conditions,
hold the scale in check.
The mango gives the best permanent windbreak, and next to it
comes the bamboo, which grows somewhat faster, but has no com-
Temporary windbreaks are numerous, and among the best are
those afforded by the pigeon pea and the various classes of bananas.
Bananas produce a very thick break in one year, and in this they
excel the pigeon peas. Where trees are planted very close together
the pigeon pea, which is a legume, should be used as a break.
The knapsack pump is the most convenient size for spraying very
young trees. The barrel pump is the most popular among the
planters of Porto Rico. As the groves are developing and more
spraying becomes necessary, it will soon be more practical to use
With these more spray can be applied and at a less expense. At the
present time some of the planters can not cover their groves in less
.than three to four weeks, and where sulphur sprays are being used,
with a repetition at intervals of two weeks, it is almost impossible
to do thorough work, as the spraying outfits are inadequate.