The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
UNIVERSITY OF FLORIDA
Agricultural Experiment Station
PRELIMINARY REPORT ON
O. F. BURGER, E. F. DEBUSK AND W. R. BRIGGS
FIG. 28.-Fruit showing severe melanose injury
Bulletins will be sent free upon application to the Experiment Station,
BOARD OF CONTROL
P. K. YONGE, Chairman, Pensacola
E. L. WARTMANN, Citra
J. B. SUTTON, Tampa
W. L. WEAVER, Perry
J. C. COOPER, JR., Jacksonville
J. T. DIAMOND, Secretary, Tallahassee
J. G. KELLUM, Auditor, Tallahassee
WILMON NEWELL, D. Sc., Director
JOHN M. SCOTT, B. S., Vice Director and Animal Industrialist
J. R. WATSON, A. M., Entomologist
R. W. RUPRECHT, Ph. D., Chemist
O. F. BURGER, D. Sc., Plant Pathologist
W. E. STOIES, M. S., Assistant Grass and Forage Crop Investi-
A. H. BEYER, M. S., Assistant Entomologist
C. E. BELL, B. S., Assistant Chemist
J. M. COLEMAN, B. S., Assistant Chemist
G. F. WEBER, Ph. D., Assistant Plant Pathologist
HAROLD MOWRY, Assistant Horticulturist
RUBY NEWHALL, Secretary
T. VAN HYNING, Librarian
RALPH STOUTAMIRE, B. S. A., Editor
MARY E. ROUX, Mailing Clerk
A. W. LELAND, Farm Foreman
K. H. GRAHAM, Auditor
RETTA MCQUARRIE, Assistant to Auditor
W. B. TISDALE, Ph. D., Assistant Plant Pathologist, Tobacco Ex-
periment Station (Quincy)
JESSE REEVES, Foreman, Tobacco Experiment Station (Quincy)
J. H. JEFFERIES, Superintendent Citrus Experiment Station
By 0. F. BURGER. E. F. DEBUSK' AND W. R. BRIGGS
Melanose is the most serious disease with which citrus growers
of Florida have to contend. It is responsible for a larger per-
centage of low-grade and unsightly fruit than any other one
thing. Stem-end rot, caused by the same fungus, is responsible
for perhaps more losses thru drops and decay in transit than all
other agencies combined. The alarming thing about stem-end rot
is that it attacks largely the choicest fruit of the tree in its toll
It is not the purpose of this bulletin to discuss stem-end rot
but, rather, melanose. However, the two diseases are inseparable
and one cannot be discussed without frequent reference to the
The fungus that causes melanose lives and reproduces in the
dead terminal twigs and branches and other dead wood of the
citrus tree. The spores (or seed-like bodies) are carried chiefly
by rain and dew to the fruit, foliage, tender twigs and dead
wood. The disease develops and spreads more rapidly during
rainy seasons. It can be distinguished by small, hard, brown,
To control melanose, the source of the disease must be re-
moved as far as is practical. Pruning out dead wood is highly
recommended and is effective as long as it can be done at a reason-
able expense. But it does not seem practical, in commercial fruit
growing, to keep trees free of all dead branches and terminal
twigs. Especially is this true of grapefruit and old seedlings.
Under present prices of labor and fruit, growers are very re-
luctant to spend more than 50 cents a tree for pruning, even in
the worst of cases. Many feel that they cannot afford to pay for
having ALL of the dead wood taken out. In fact, it is next to
impossible to prune out all dead terminal twigs. So, it seems
that to control melanose from a practical standpoint, pruning
must be supplemented by spraying.
'Mr. DeBusk is county agent of Lake County, and Mr. Briggs is county
agent of Manatee County.
124 Florida Agricultural Experiment Station
The Florida citrus grower is realizing more and more each
year the importance of producing bright fruit. The questions
being asked are: "How can I produce bright fruit?" "What
causes such a large percentage of russet in my fruit?" The fact
that the market is willing to pay a higher price for bright fruit,
proves to the grower that it is profitable to produce such fruit.
One of the greatest hindrances in selling Florida citrus fruit
is its appearance. Just as soon as the grower raises the quality
of his fruit, just that soon will he experience a greater demand
for his product.
There are three disease and one animal pest of Florida citrus
fruit which cause it to russet. The worst, and th6 one causing 60
percent of the russets, is melanose. The other two diseases may
be classed as ammoniation and scab. The pest is rust mite and
it causes considerable russeting.
Melanose is sometimes called "rust," owing to the color, pro-
duced by it, on the fruit and leaves. The disease makes its ap-
pearance on the surface of leaves, twigs and fruit as small, hard,
raised, reddish-brown spots or specks scattered over the surface.
The spots are gen-
erally round with
ia smooth glazed
Surface. In slight
W 7 attacks the spots
are scattered and
give a sandpaper-
like feeling to the
touch. Where the
I Idisease is severe
the spots often run
S;. together to form
4 ". large hard glazed
patches (see fig.
., .28). Sometimes the
FIG. 29.-Grapefruit with melanose streaking.
(From Bul. 145, Fla. Agri. Exp. Sta.) ing a tear-stained
Bulletin 167, Controlling Melanose
appearance. In many groves the disease is so severe that the
fruit is dwarfed, the leaves drop off and the young stems are
covered with a hard brown crust. Some fruit, when it approaches
maturity, is so badly scarred that it cracks open.
The symptoms of the disease appear on the leaves as cir-
cular markings (see fig. 30). These markings may also occur
on fruit, but are more gen-
eral on the leaves. The
circles vary in diameter
from an eighth to a quar- 0' -
ter of an inch. The out-
line may be a continuous f '-
raised line, but more fre- ,r
quently it is composed of
a series of small raised 4 '
dots. These circles are
supposed to be formed in '
the following manner:
Many spores are held in
a drop of water; on ac- "
count of the surface ten-
sion of the drop of water
f the drop of waterFIG. 30.-Melanose, showing looped rows of
the spores soon lodge on markings. (From Bul. 108, Fla. Agri.
its edge; when the water Exp. Sta.)
evaporates the spores remain deposited in a circle where they
cause the peculiar markings described above (see fig. 31).
The surface cells of the fruit or leaf are soon killed and at
first the dead area is somewhat sunken. Later the living cells
beneath this area, becoming stimulated, grow and push the dead
area above the surface, thus forming the characteristic markings
DISTRIBUTION OF MELANOSE
Melanose is distributed thruout Florida. It seems, however,
from a questionnaire sent out that the disease is more prevalent
along the West Coast and thru the middle of the peninsula than
on the East Coast.
From data gathered, grapefruit and seedling oranges ap-
parently are more affected by melanose than any other variety.
In all, 4,000 letters were sent out from the Experiment Station
to ascertain the prevalence of melanose, but only 500 were
Florida Agricultural Experiment Station
From those letters the average percentages of melanose in the
various counties were obtained. This, of course, may be some-
what inaccurate, but it is believed that it is approximately cor-
rect. Certainly it approximates the conditions in the state. There
was a great variation in the answers received. Some reported
1 percent of their fruit russeted by melanose, while others com-
plained of having 95 percent so affected. Counts were made last
fall in a certain packing house and it was found that 60 percent
of the russets were caused by melanose.
According to the answers to the questionnaire and the counts
made at the packing houses, the following figures are given
to indicate the amount of melanose-affected fruit passing thru
the packing houses in various counties:
County Melanose County Melanose
Brevard ............ --.......-......... 15 Orange .................... ... .. 15
Citrus .......... --...... .............-- .... 6 Osceola ............ .. ......--- 40
Dade ........................................ 8 Palm Beach ......- ............. 8
DeSoto ................- ..-........-.. .... 13.5 Pasco .-......... ... ..- --- --- 11
H illsboro ............................... 15 Pinellas ......... ................. .13
Lake ..............----.....--...--.......--11 Polk .....................-----. 10
Lee .--.....-......... ..........-......--- 19 Putnam -...- ... ... ............. 24
Manatee ......................-....- 10 St. Johns --. ..............-- 4
M arion ................----....... ............19 St. Lucie ..............-................ 6
Okeechobee ...... .................... 8 Sem inole .......... ...........16
Volusia -........-- ..... 7
CAUSE OF MELANOSE
Melanose is caused by the fungus known as Phomopsis citri
Faw. This fungus is also responsible, as previously said, for the
disease known as stem-end rot. It lives in the dead wood of the
trees where it produces its spores which ooze out to be washed
down to the young leaves, twigs and fruit, thus causing the
For melanose to be severe in a grove there must be several
contributing factors. Dead wood is necessary, and this may be
formed by the killing of young twigs and branches by freezes,
by severe infestations of scale and by diseases. A slight freeze
may be only sufficient to cause the tree to drop its leaves. The
spores in being washed down the twigs find their way into an
old leaf scar. The fungus then will grow thru the twig and kill it.
Or, the spores may enter a ripe fruit at the stem end, and the
fungus will grow up the stem, away from the fruit, killing the
twig for a distance of several inches. Perhaps the killed twig is
Bulletin 167, Controlling Melanose.
only an inch long, but that is sufficient to harbor the fungus and
produce millions of spores.
The fungus cannot go thru the healthy bark and kill the twig.
It must have some wound or natural opening thru which to enter.
It causes stem-end rot only after the forming of the abscission
layer, the layer that separates the fruit from the twig. The small
cracks in this layer are sufficient to give the fungus entrance.
Many trees were examined where stem-end rot was present,
FIG. 31.-Melanose on grapefruit. Rows of spots. (Magnified.) (From 1911
An. Rpt. Fla. Agri. Exp. Sta.)
but the disease was found only on those trees which were ripen-
ing their fruit and where the abscission layer had been formed.
A bad attack of scale kills many small twigs, into which the
fungus finds a ready entrance. Soon the twigs become filled with
the reproductive bodies of the fungus which are formed in the
bark. Of course, this also happens in the case of all wood killed
by dieback or other diseases.
Another great factor necessary for the spread of the disease
is rain or heavy dew. The spores of the fungus are imbedded
in a gelatinous-like substance which swells when moist; this
Florida Agricultural Experiment Station
pushes the spores out of the reproductive body bearing them.
Then the rains wash the spores down to the young leaves, twigs
and fruit, and soon disease is the result (see fig. 32).
Only young and growing tissues are susceptible to melanose.
In the experiments forming the basis of the conclusions drawn
in this experiment young trees were placed in a moist chamber
and spores from a pure culture sprayed onto the young leaves.
FIG. 32.-Typical melanose injury to citrus leaves, stems, and fruit. (From
Bul. 145, Fla. Agri. Exp. Sta.)
Small spots began to develop in from three to seven days. A
spot at first is brown and sunken but later becomes raised. It
was found that leaves from four to six weeks old became immune
and, when sprayed with the spores of the fungus, did not develop
WHEN DOES FRUIT BECOME IMMUNE?
The question then arose, when does the fruit become immune?
Young citrus fruits were picked at various times and brought
Bulletin 167, Cnitr, ;linl Melanose
into the laboratory and placed in a moist chamber. They were
sprayed with a water containing the spores, and. the dis~' 'M
developed in from three to seven days. Young fruits for this
purpose were picked weekly from April 22 to May 20. All were
infected. With each lot a check was kept. Other fruits were
placed in a moist chamber and sprayed with distilled water;
these did not develop the disease. On May 20, specimens of
Duncan grapefruit and Pineapple oranges were gathered. These
were sprayed with spores as in the previous experiments, but
melanose did not develop. This would indicate that the fruit
becomes immune to melanose about the last of May.
It has been noticed that fruit sprayed in the field with bor-
deaux-oil in the early spring remained free from melanose after
June rains began, even tho the spray material had been washed
off. On the other hand, June bloom was noticed to become badly
affected with the disease. Hence, the conclusion may be drawn
that the fruit becomes immune about June 1.
H. J. Webber, of the United States Department of Agriculture,
was the first person to describe this disease. He found it at
Citra, Florida, in 1892. Dr. Webber immediately began spraying
experiments to control it. His first spray was 6-31/-50 bor-
deaux mixture, which he applied one month after the tree began
to bloom, repeating once a week for ten weeks. His second spray
was ammoniacal copper carbonate, 5 ounces to 50 gallons of
water. This spray was repeated once a week for eight weeks.
His records show that melanose was effectively controlled but
that the trees and fruit were seriously injured by scale.
B. F. Floyd, in the 1911 annual report of the Florida Agricul-
tural Experiment Station, says that the pruning out of dead
wood lessens the disease.
H. E. Stevens, in Bulletin 145 of the same station, recommends
pruning for the control of melanose. He believes, according tc
that bulletin, that if all dead wood is pruned out of the tree, there
will be no melanose. It is believed that Prof. Stevens is right
on this point, but it is contended that in the large, commercial
grove, it is impractical to remove all dead wood by pruning.
There are many small twigs, only an inch or two long, that are
Florida Agriciultral Experiment Station
A SPRAY SCHEDULE FOR CITRUS
1 Grapefruit Sabh
2 Grapefruit Rust Mites
7 and Scale Insects
Oranges Rust Mites
Grapefruit Rust Mites
8 and Tearstain
__-- i_ ---
9 and Whitefly
Oranges Scale Insects
10 and Rust Mites
(32 Baume); 21/ gals. in
100 gals. water
21/2 gals., and 13 ozs.
nicotine sulphate to 100 gals.
of the spray solution
2%1 gals. in 100 gals. water
TIME OF APPLICANT
JUST BEFORE THE FIRST
FLUSH OF GROWTH
JUST BEFORE THE PETAL
WHEN 1/3 TO '/2 THE
PETALS ARE OFF
7 TO 10 DAYS AFTER
TO /2 THE PETALS
21/2 gals. in 100 gals. water 14 T 20 DAYS AFTER 1/
THE PETALS ARE OFF
1%1 to 2 gals. in 100 gals. APRIL 5TH TO 15TH
Oil emulsion, 1% plus 21/ lbs. IN MAY WHEN THE
dry soda-sulphur in 100 gals. FRUIT IS AT LEAST 1
water INCH IN DIAMETER
11/2 to 2 gals. in 100 gals.
Oil emulsion 1%
PREFERABLY IN SEPT.
OR OCT., BUT CERTAINLY
BEFORE FEB. 1st.
,1/ to 2 gals. in 100 gals. NOVEMBER TO JANUARY
Bordeaux mixture plus 1% of oil in the form
of an oil emulsion stock solution. (See remarks
under No. 7.)
5s To be applied, if scab infections appear on the
new growth, or, if rainy weather favorable for
scab follows No. 1.
Add the nicotine, if 25 or more thrips to the
bloom are present. If thrips are abundant but
no scab, use 1'/ gallons lime-sulphur and 2
pounds nicotine-sulphate solution to 100 gal-
Lime-sulphur will also kill rust mite and red
Spiders, and for thrips 12 ounces nicotine-sul-
phate are added. Bordeaux-oil is not as effec-
tive as lime-sulphur for above insects.
TO /z To be given if rainy weather favorable for
scab or melanose follows No. 4.
If any two lime-sulphur sprays out of Nos. 3,
4, and 5 have been given, this can be omitted;
otherwise, this is the critical spraying for rust
mite on grapefruit.
The oil emulsion should be used so that the di-
luted spray material will contain I 7' oil; that
is, if the emulsion contains 669r oil, 11/, gal-
lons would be required for 100 gallons water.
On oranges this is the critical rust mite spray,
if the fruit has not received any previous lime-
To be given, if scale insects or whitefly are
To be given only if rust mites are noticeable.
The accompanying spray schedule
represents the combined judgment of
W. W. Others, entomologist, and J.
R. Winston, pathologist, U. S. Depart-
ment of Agriculture; O. F. Burger,
pathologist, H. E. Stevens, former
pathologist, and J. R. Watson, ento-
mologist, Florida Experiment Sta-
tion; and E. W. Berger, entomologist,
Florida State Plant Board.
This combined schedule is based on
the work to date of state and federal
investigators and represents their
composite judgment regarding the
control of certain citrus insects and
diseases by spraying. The five appli-
cations in heavy type (Nos. 3, 4, 7, 8
and 9) are recommended as sufficient
for the control of the enemies usually
destructive on grapefruit in an aver-
age season, provided the spraying is
done thoroly. Oranges will ordinarily
require only four applications (Nos.
4, 7, 8 and 9). Under conditions es-
pecially favorable for disease or in-
sect increase some of the remaining
applications may be required also.
The scab applications indicated for
grapefruit also may be required on
highly susceptible varieties of or-
anges, especially of the kid glove type.
Application No. 3 will be required
on oranges only when thrips are
Be cautious about using lime-sul-
phur solution when the temperature
is above 900 F. If applied under this
condition, use the weaker strength and
be sure of the accuracy of the Baume
test and of the diluting.
Bordeaux mixture requires 3 pounds
bluestone and 3 pounds lime in 50 gal-
lons water. Get the best grade of
fresh stone lime obtainable. Never use
air-slaked lime. If hydrated lime or
an inferior grade of quick lime must
be used, make it 4 pounds.
Copies of this spray schedule may be obtained free by writing to the Agricultural Extension Division, University of Florida, Gainesville,
Bulletinz 167r, Controlling72 MelanLose
and asking for Extension Bulletin 30
Bulletin 167, Controlling Melanose
TABLE 14.-THIS SHOWS THE PERCENTAGES OF FRUIT AFFECTED BY
Block sprayed Block sprayed Percentage
with bordeaux-oil with oil only difference
Russets caused by melanose.... 9.4% 19.3% 9.9
Culls caused by melanose........ .6% 1.2% .6
Drops caused by melanose
and stem-end rot................ 1.5%, 2.4% .9
Based on last year's percentages of the different grades and
on the prices received for Florida fruit in the four leading mar-
kets of the United States, this increase in the saving from culls
and in the quality of the fruit, as the result of spraying with
bordeaux-oil, means an increased return for the fruit of 16 4/5
cents a box. Spraying costs 13 cents to the tree, or approximately
3 1/4 cents a box, there being four boxes to the tree. This would
leave a net profit from spraying of 13 1/2 cents a box, or 450
percent on the investment.
A second grove, situated in a hammock, was selected for
further experiments. This grove was heavily infested with scale.
It was divided into the following plots:
Plot 1: Trees pruned, not sprayed.
Plot 2: Trees pruned, sprayed once.
Plot 3: Trees pruned, sprayed twice.
Plot 4: Trees not pruned, sprayed once.
Plot 5: Trees not pruned, sprayed twice.
Plot 6: Trees not pruned, not sprayed.
The spraying was done on March 20 and April 5 with 3-3-50
bordeaux-oil. Notes were taken at various intervals during the
season. A few weeks after the rains began it was noticed that
the sprayed trees were nearly free from melanose, while Plot 1
was badly affected with melanose. No difference could be seen
between Plots 1 and 6, as regards the amount of melanose.
After the rains were over, scale began increasing to such an
extent on the sprayed trees as to become very noticeable. The
grower was urged to spray with oil, but he neglected to do so and
the fruit was badly infested with scale at picking time. How-
ever, it was seen that there was no more melanose on the plot
sprayed once than on the plot sprayed twice. At picking time
the fruit was run thru the packing house where two grades,
brights and golden, were made. In reading the following data,'
Florida Agricultural Experiment Station
are capable of producing melanose and stem-end rot.
should be pruned of its dead
wood; but it is believed that from
BORDEAUX-OIL KILLS FRIENDLY FUNGI
The greatest objection to bordeaux mixture as
citrus trees is that it kills friendly
which many growers
use to combat scale and whitefly
Therefore, if the grower wishes
to use bordeaux-oil to control melanose, he cannot depend upon
to control scale and whitefly,
spray with oil emulsion for this purpose.
SPRAYING EXPERIMENTS OF 1921
In the spring of 1921 an experiment to control
in a grove
four-box crop of
contained about as much dead wood as is found in the average
The grove had been fairly well cultivated and
Prior to the beginning of the demonstration on March
14, the grove was sprayed with Black leaf
40 and lime-sulphur
(1 to 40)
to control thrips, rust mites and scab.
On May 7, a part of the grove
sprayed with bordeaux-oil
emulsion, 3-3-50 bordeaux and 1-percent oil, to control melanose
and the other part was sprayed with only a 1-percent oil emulsion
to control scale and whitefly.
This spraying was preceded by a
long dry spell and followed by a heavy rain on May 10.
fall up to May
10 was far below normal.
No other sprayings,
up to that time, had been made in this grove in 1921.
The Increased Returns from Spraying
Careful counting and grading of the fruit as closely
sible at this stage of
development, on October
Florida Agricultural Experiment Station
it should be borne in mind that the golden from the plots Which
were pruned and sprayed were classed as such on account of scale
infestation, while the golden from the pruned and the check
plots were classed as such on account of melanose.
TABLE 15.-RESULTS FROM SPRAYING GRAPEFRUIT GROVE NO. 2
Percentage of Percentage of
Pruned ... ... ... .. .... .... ... .. .. 64.38 35.64
Pruned and sprayed................ .... 69.08 30.87
Sprayed -............. .......... ....... ...........I 58.58 41.41
Check: No pruning; no spraying........... 33.35 66.64
From the above results one can see that it pays to spray, while
the pruned plot also shows up better than the plot that was only
sprayed. Yet it must be remembered that, as said above, the
golden in the sprayed plot were caused mostly by scale infesta-
tion. For this reason it was decided to spray again during the
spring of 1922 and on a bigger scale. It was known that growers
could be found who were controlling scale and whitefly by spray-
ing and who knew it could be done When bordeaux-oil was used
in the groves.
SPRAYING EXPERIMENTS OF 1922
In the spring of 1922 eleven experiments were started, ex-
periments in which 3-3-50 bordeaux spray, plus 1 percent of oil
emulsion, was used for the control of melanose. Eight experi-
ments were in Lake County, two in Manatee and one in Brevard
on the East Coast. The total acreage under experimentation was
1,255, approximately. The largest single acreage was in Manatee
County, where about fifteen thousand trees were sprayed.
The data were gathered in two ways. In most of the groves
the fruit on the trees had to be counted and classified into brights,
golden and russets. Fortunately, in the largest experiment
the fruit was classified in the packing house. In the field, only
those fruits were counted which could be reached easily and in-
spected as the counters stood on the ground.
All growers know that melanose is worse at the base of a tree
than at the top. This is so because generally there is less dead
wood near the top of the tree than lower down. In all the experi-
mental groves oil spray was used in 1921 for scale and whitefly;
and in 1922, sometime between July and September, depending
upon the need of the grove and the convenience of the grower,
TABLE 16.-HERE IS SHOWN THE RESULTS OF SEVERAL EXPERIMENTS IN SPRAYING ORANGES AND GRAPEFRUIT WITH BOR-
DEAUX TO ONTOTR, MELANOSE
SPRAYED WITI BORDEAUX
Kind of No. of grove
fruit and county
Time of Percentage Iercentagoe
.spraying of brights of goldlens
NOT SPRAYED WITH BORDEAUX
PIerceLntag)e I'Percentage'llt I'cerce ntiage P 'rcentagft'i
of f russeth of brights of goldens of russ.ts
Florida Agricultural Experiment Station
another spraying was made for the same purpose. The rust mite
was also kept in check by either the lime-sulphur spray or sulphur
dust. In all the experiments the check plots were treated in the
same manner as the plots sprayed with bordeaux-oil. All groves
were pruned, that is as much of the dead wood was pruned out
as was commercially practical. As was stated previously, only
groves badly affected with melanose were selected, but in these
the growers were doing all they could to produce bright fruit.
In Table 16 is given the kind of fruit sprayed, whether grape-
fruit or oranges, the number and place of the grove, time of
spraying, and percentages of the different grades of fruit in the
sprayed and unsprayed plots. It is seen that the average per-
centages differ very little between the oranges and grapefruit.
In Experiment 1, carried out in 1921, the cost of spraying was
13 cents a tree. That was in an ordinary grove. In Experiment
9, running water would be secured in the grove and, the item of
hauling therefore being eliminated, the cost was reduced to 8
cents a tree. Cost figures are given below for spraying a grove
of 15,000 trees.
Labor ................ ............. .................. $436.00
Lim e ........ ....... ... .. ....... .... ...................... 85.00
Bluestone ............. ............... .. ........ ... 160.00
Oil emulsion ..... -....... ............ ............... 442.00
Overhead ............ ...... ............ ...... 100.00
Total...................... ....... ...... ......$1,223.00
Cost to the tree........................- -........-.. .0816
Cost to the box....................... --....... ............ ... .016
This is a grapefruit grove and the trees averaged five boxes
each. This grove was so large it took about thirty working days
to spray it.
Suppose one had 1000 boxes of oranges which had been sprayed
and would sell on the market for the following prices:
665 boxes of brights @ $5.79..........--............. ...$3,860.25
285 boxes of golden @ 5.30.............................. 1,510.50
50 boxes of russets @ 4.07......................... ...... 203.50
Total net receipts..... ............ .... ......... .. ..$5,574.25
According to the results shown in Table 15 of sprayed and un-
sprayed fruit, he would receive for the unsprayed fruit at the
255 boxes of brights @ $5.79...................... ..... $1,476.45
304 boxes of golden @ 5.30-..................-...... 1,611.20
441 boxes of russets @ 4.07................................ 1,794.87
Total net receipts.............. ................. $4,882.52
Bulletin 167, Controlling Melanose 137
This would mean that he would have gained $691.73 by spraying.
In like manner, determine the difference obtained by spraying
grapefruit, figuring on the basis of 1000 boxes as in the preceding
690 boxes of brights @ $5.80...................................$4,002.00
240 boxes of golden @ 5.35...................... .............. 1,284.00
70 boxes of russets @ 4.06....................... ........... 284.20
Total receipts ............. ......... ... ............$5,570.20
246 boxes of brights @ $5.80.................................$1,426.80
333 boxes of golden @ 5.35................................ 1,781.55
421 boxes of russets @ 4.06.................................. .. 1,709.26
Total receipts ...... ............... ....................$4,917.61
The gain by spraying would in this case be $652.39, or more
than 50 cents a box. The selling price of the fruit used in these
calculations was the average price received by a certain organi-
zation in the state for the season of 1920-21.
HOW TO MAKE BORDEAUX-OIL EMULSION
The success of spraying with bordeaux-oil emulsion depends
largely upon the method of making it. While the homemade bor-
deaux is more or less troublesome to prepare, it is recommended
for this work. The oil emulsion used may be the cold-stirred or
the government-formula boiled emulsion, or any of the good
proprietary oil emulsions.
In making bordeaux mixture observe the following directions:
Dilute the required amount of bluestone in a container which
contains water to half the amount of spray to be made. Dilute
the required amount of lime in a separate container which also
contains water to half the amount of spray to be made. Then,
and at the same time, run the contents of the two containers into
a third container, stirring the combined mixture as the two are
being poured together. Now add the oil emulsion before the
stirring is stopped.
For convenience the bluestone and lime can be made into stock
solutions containing one pound to each gallon of water.
Stock A, Bluestone: Dissolve at the rate of 1 pound to the
gallon. Put 50 pounds of bluestone into a clean feed or fertilizer
bag and suspend it at the top of a 50-gallon barrel of water. It
will dissolve over night as a rule. Dissolving can be hastened by
using hot water or by letting the water run into the barrel thru
Florida Agricultural Experiment Station
the bag of bluestone. Never use a metal container for this. AL-
WAYS STIR THIS STOCK SOLUTION BEFORE TAKING ANY
Stock B, Lime: Quicklime should be used in making bordeaux.
Slake 50 pounds of lime and dilute it to 50 gallons. Be careful not
to drown or burn the lime while slaking. ALWAYS STIR THIS
STOCK SOLUTION BEFORE TAKING ANY OUT.
FOR DIFFERENT AMOUNTS OF EMULSION
In making 200 gallons of the mixture, use 12 gallons of stock
A, diluted to 100 gallons, and 12 gallons of stock B, diluted to
100 gallons. Run both of these into the sprayer at the same time
with the agitator going. Then add 3 1/3 gallons of oil emulsion,
and the spray material-bordeaux-oil emulsion-is made.
To make 50 gallons of spray, use 3 gallons of stock A, diluted to
25 gallons, and 3 gallons of stock B, diluted to 25 gallons. Mix
as above and add 3 quarts of oil emulsion.
To make 100 gallons of spray, use 6 gallons of stock A, diluted
to 50 gallons, and 6 gallons of stock B, diluted to 50 gallons. Mix
as above and add 1 2/3 gallons of oil emulsion.
To make 150 gallons of spray, use 9 gallons of stock A, diluted
to 75 gallons, and 9 gallons of stock B, diluted to 75 gallons. Mix
as above and add 2 1/2 gallons of oil emulsion.
To make 250 gallons of spray, use 15 gallons of stock A, diluted
to 125 gallons, and 15 gallons of stock B, diluted to 125 gallons.
Mix as above and add 4 1/6 gallons of oil emulsion.
To make 300 gallons of spray, use 18 gallons of stock A, diluted
to 150 gallons, and 18 gallons of stock B, diluted to 150 gallons.
Mix as above and add 5 gallons of oil emulsion.
When it is not practical to use a central filling station and the
sprayer is filled from pipelines in the field, the stock solutions
may be made at the rate of two pounds to the gallon in place of
one, and used accordingly. This is a little harder to do than using
one pound to the gallon, but it can be done. The stock can be
carried on an extra wagon together with empty barrels for mix-
ing. The tank can then be filled by the suction hose or by bucket.
THE CENTRAL STATION
For convenience in filling the sprayer, one should have a plat-
form for the barrels high enough so that the mixtures can run
from the barrels into the sprayer. This does away with the
Bulletin 167, Controlling Melanose
hard work of lifting it in by buckets. This platform should be
large enough to hold the two barrels of stock solution and the
number of barrels needed for diluting. For the 200-gallon tank
the platform would have to hold six 50-gallon barrels.
If it is impractical to use the above method of mixing the
bordeaux, the following method may be used: Pour the amount
of diluted lime solution into the spray tank, set the agitator to
going and add slowly the dilute bluestone solution. After the two
solutions have been mixed, add the required amount of oil-emul-
sion while the agitator is still going.
The damage done by the fungus which causes melanose is
when the leaves, twigs and fruit are young. If one waits to spray
until melanose is already on the fruit, the damage will be done
and spraying will be of no avail in controlling the disease.
Leaves and twigs can be infected only while very young;
after the leaves are from three to five weeks old they cannot be
infected. Hence, the time to spray is when the fruit is young.
The spray makes a coating over the fruit and leaves so that the
fungus cannot infect them. Experiments conducted last season
showed that, if the trees are sprayed from ten to twenty days
after the bloom has dropped, the fruit will be protected from this
WHAT SPRAY TO USE
Bordeaux-oil spray has been used for experimental purposes
and has given good results. The following formula was used:
Bluestone 3 pounds, rock lime 3 pounds (use only a good grade of
lime), water 50 gallons, and some good oil emulsion 3 quarts.
Mix the ingredients of the above formula in the following man-
ner: Slake 50 pounds of rock lime in a barrel and add enough
water to make 50 gallons of the solution. Hence, one gallon will
contain one pound of lime. Suspend a sack containing 50 pounds
of bluestone into the top of a barrel of water. After the bluestone
has dissolved, take out the sack and add enough water to make
50 gallons of this second solution. Hence, one gallon of bluestone
solution will contain one pound of bluestone.
Now take 3 gallons of the lime solution, pour it into a third
barrel and add 22 gallons of water. Take 3 gallons of bluestone
140 Florida Agricultfraal Experiment Station
solution, pour it into a fourth barrel and add 22 gallons of water.
Pour thru a strainer the contents of the third and fourth barrels
into the sjiray tank, at the same time stirring the two mixtures.
After these solutions are well mixed and while the agitator is
still going, add 3 quarts of an oil emulsion. Always mix the solu-
tion in the above proportions regardless of the size of the spray
tank. The solutions, when mixed in the tank, should be used the
same day. The lime and bluestone solutions, kept separate in
the barrels, will keep thru the spraying season.
HOW TO APPLY THE SPRAY
A power sprayer must be used and the pressure should not be
less than 200 pounds. If the spray gun is used, the pressure
should not fall below 250 pounds. To do good and thoro work,
the use of spray rods is recommended.