Some reasons for spraying to control insect and mite enemies of citrus trees in Florida

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Contribution from the Bureau of Entomology
L. O. HOWARD, Chief

ashington, D. C. January 26, 1918

it SOME REASONS FOR SPRAYING TO CONTROL INSECT
4 AND MITE ENEMIES OF CITRUS TREES IN FLORIDA.

By W. W. YOTHERS,
Entomological Assistant, Tropical and Subtropical Fruit Insect Investigations.

CONTENTS.
Page Page
Sete s oeine'= se 1 | Better grades of fruit bring better prices. ...- 13
?P Baw Orimportance..-.-2------<s--2-.---=-%- 2 | Spraying scheme for controlling citrus pests- 15
- Injury totreesand fruit .........------------ FAINCOStOLSDEAVINGE S222 Saco cea saeicla les oisinin seein 16
Benherrading Of fruit. -..---.-.----+---+--+--- Be PRROnts and: PONEHUS=co~ cin 2.50 Sa a <moe = oe = 17
Re PGONCIUSION Gs eisace cco ceics tec ce cose ecw cence 18

Hi) §©Reductionin size caused by insects...-.-----
ie

GRADUAL ADOPTION OF SPRAYING.

‘Among Florida growers there have been developing during late
@ years what may be called two schools for the control of citrus
i pests. One of these favors dependence upon natural enemies; the
other, upon artificial methods, particularly spraying. The relative
merits of these two general methods of control are not discussed
| here, since, as time passes, it becomes more and more evident that
#4 there is room for both under the widely varying conditions sur-
fe rounding Florida groves. Enthusiastic supporters of control by
# natural agencies such as entomogenous fungi do not believe that the
Hi lowering of the grade and the reduction in the size of the fruits and
Hi of the yield, if any, are of sufficient importance to demand attention.
#4 Or perhaps the case may be stated more fairly by saying that they
ii believe that it is more profitable to use no measures for the control
of pests, contending that it pays better to grow the lower grades
f fruit without treatment than the better grades with treatment.
i It is interesting, however, and very encouraging to note the gradual
i adoption of a system of spraying for the improvement of orchard
# conditions by men who, only a few years before the Federal Bureau
Hf of Entomology began its demonstration work, believed in, and de-
Hf pended upon, natural agencies as the best all-round method of con-
Hi) trol. This change has come partly through a realization that fungi

21698°—18—Bull. 645 1

Monograph

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cSP~Yo
ie.

yd BULLETIN 645, U. 8S. DEPARTMENT OF AGRICULTURE. ~

parasitic on certain injurious insects, excellent as they are, have
fallen short of what was expected of them, but more as a result of a
spraying system developed by the writer, which, by taking all pests
into consideration instead of merely the white flies, has proved the
direct financial gain that will follow the intelligent application of
spray mixtures. It is to certain advantages of this system of spray-
ing that attention is called in this bulletin. Perhaps the best argu-
ment in favor of spraying is to be found in the difficulty experienced
in securing the same grove for demonstration purposes two or three
years in succession. Once the owner has seen with his own eyes the
benefits resulting from careful and well-timed spraying, he refuses
to accept the losses that he knows will come to him or his company
through the setting aside of blocks of trees to serve as checks in com-
munity demonstration work.

PESTS OF IMPORTANCE.

Of the total damage caused by insects and mites to citrus in
Florida, more than 95 per cent may be attributed to six species. In
the order of their destructiveness, these are the citrus white fly,’ the
purple scale,? the rust mite,? the red scale,* the cloudy-winged white
fly,> and the red spider. There are several other pests of secondary
importance, such as the woolly white fly,” the purple mite,® and the
chaff scale.2 The citrus white fly now infests nearly all the groves
in the State. The purple scale is found in greater or less numbers on
every citrus tree.

INJURY TO TREES AND FRUIT.

The presence of these pests on the trees and fruit produces
blemishes which cause fruit to be placed in a much lower grade than
would be the case if these blemishes were not present. While the
excellent methods of washing the fruit remove nearly all the sooty
mold which follows attacks of the white fly, usually some of itis left
near the stem end. When this is present the fruit is placed in a grade
lower than if it were absent. The presence of scale insects on the fruit
lowers the grade, and, when these are abundant, makes the fruit
practically unmarketable unless the scales are removed by hand wash-
ing. Perhaps the greatest cause for lowering the grade of fruit is
the blemish following rust-mite injury. All these pests devitalize the
trees, and this type of injury is much more important than the low-
ering of the grade of the fruit, because the yield is reduced. This

1 Dialewrodes citri Ashmead. 6 Tetranychus sexmaculatus Riley.

2 Lepidosaphes beckii Newman. 7 Aleurothrivus howardi Quaintance.
* Briophyes oleivorus Ashmead. 8 Tetranychus citri McGregor.
4Chrysomphalus aonidum Lipneus. » Parlatoria pergandii Comstock

5 Aleyrodes nubifera Berger, now known
as Dialeurodes citrifoli Morgan.

= fda

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 3

devitalization is well known and admitted by the citrus growers,
but few really appreciate the magnitude of this type of damage.
Thousands of trees have been seen so injured by the purple scale that
all the inside foliage and small limbs had been killed, and only a
mere “shell” of foliage remained. In one small community in 1915
it was estimated that the damage amounted to $30,000. It cost four
times as much to remove the dead wood resulting from insect attack
as it would have cost to prevent the damage, and two crops of fruit
were lost in addition. At least 75 per cent of the total damage could
have been prevented for less than $2,000. Many citrus growers,
realizing that this injury to the trees follows severe scale infestation,
apply extra fertilizer so that the trees may have enough nourishment
not only for the production of a good crop of fruit, but also to meet
the demands made upon their vitality by the feeding scales. The be-
lief is general that more fertilizer is required to get results in a
grove heavily infested with scale insects and white flies than in one
that is comparatively free from these pests.

To express the extent of this devitalizing effect in a statistical way
or on a percentage basis is very difficult. In the two instances given
below the damage caused by insect pests and mites is most strikingly
shown. Although it is only proper to admit that these two cases rep-
resent extreme injury by pests, they indicate that the devitalizing
effect which results in diminished yield is much greater, on an aver-
age, than most growers have thought possible.

In one instance a row of 16 trees was left unsprayed for three sea-
sons, 1913, 1914, and 1915. The remainder of the grove was sprayed.
The citrus white fly was making its first appearance in the grove.
During the year 1913 there was little or no difference in the yields of
the sprayed trees and the unsprayed check trees. In 1914 the un-
sprayed row had about 5 boxes of fruit, dnd the adjoining row of
16 sprayed trees about 60 boxes. All common species of fungi para-
sitic on the white fly and scale insects were present in great abun-
dance. In 1915 the difference was not so great; the unsprayed row
had about 20 boxes of fruit, and the adjoining sprayed row about 50
boxes.

As another instance, in a grapefruit grove at Safety Harbor 84
trees left without treatment during the summer of 1914 averaged
two-thirds of a box per tree less than the trees adjoining which were
sprayed. The reduction in the yield due to failure to spray was
caused by the smaller size of the fruit resulting from rust-mite
attack. There seems to be no evidence that the actual number of
grapefruit on the unsprayed trees was less than on the sprayed trees.

During the year 1915 the same trees received the same, treatment
as during 1914. The sprayed trees had at least a good half crop,
or about four boxes per tree. The trees adjoining which were left

}

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A. BULLETIN 645, U. S. DEPARTMENT OF AGRICULTURE.

unsprayed during both years yielded only from one-half to one box
per tree. This difference was so marked that all the laborers in the
grove noticed it as early as August 1.

THE GRADING OF FRUIT.
PRESENT STATUS.

The percentage of first-grade fruit shipped out of Florida is not
as great as it should be. To illustrate this point several tables have
been prepared which give the percentages of the various grades
shipped. These data have been obtained with difficulty. At first it
was thought that information could be obtained from the growers.
As a matter of fact the growers, as a class, do not know the percent-
age of the fruit in the different grades or the price received for the
respective grades, for the reason that a large percentage of the citrus
crop is sold on the tree, and shipped by those commission firms own-
ing groves. |

No information regarding the percentages of the various grades
shipped could be obtained from the shipping companies: One im-
portant firm wrote that such large quantities of their fruit had been
sold at so much per box, regardless of grade and size, that they were
unable to give any information about grades and prices. The reports
of the New York auction and the Florida Citrus Exchange were
available.

The grading of fruit in Florida is in a most chaotic state. Certain
grades marked “fancy” bring less money than third or fourth-
grade brands. There are no standards for the various grades of
fruit; the different grades vary as the season advances, and from
year to year. It is very difficult to place each brand of fruit in its
proper place. Attempt, however, was made to place it just as the
shipper had intended. The Citrus Exchange key to the various
brands was followed for all Exchange fruit. Wherever the word
“ fancy” occurred, this was placed in the first grade, “ bright ” in
the second, and so on. This was strictly adhered-to. The follow-
ing table will explain this more fully:

First grade. Second grade. Third grade. Fourth grade. Fifth grade.
ancy se opce nace Bright. 2s .c.- assets Goldenten esas sme cs Russetjze2eeseeee Plain.
Stripes Nom scene prLapes Bits ieseeass she Stripes wR secaes-ssene - SiripesYe- Gece Big Cypress.
Blue. 252s. ese seers PROGE 2 Peer titers Bees ene Yellowsos-25 2" Plain.
Deerfield F_. DeerfisldsBe ees. 1s Deerfield Gis: -2c02.. .a|$i5 ec sees ee eee
Deeks Fancy... Je R. We Choice: ----- DR We Golden’ 220." scenes eee
Ballsiof Jesseese = -2215- Florida Sunshine... ADOX. aaa eapeeee

In order to arrive at the best estimate of the grades of fruit shipped
from Florida at present it seemed best to adopt two fairly distinct
methods to determine this for New York City and compare the re-
sults with those obtained from other sources.

i

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 5

By the first method the records of fruit sold on four days of each
month in New York City were taken into consideration. Usually
the days selected were the 3d, 10th, 20th, and 28th or 30th of each
month, but other days might have been chosen just as well. The per-
centages of the various grades of fruit shipped, based upon the rec-
ords for these representative days, are given in Table 1.

TaBLE 1.—Percentages of various grades of oranges and grapefruit shipped
from Florida to New York City during the season of 1915-16.

Oranges. Grapefruit.
_ Month.
First |Second| Third | Fourth] Fifth | First |Second| Third | Fourth! Fifth
grade. | grade. | grade. | grade. | grade. | grade. | grade. | grade. | grade. | grade.
November.......-.- 8.17 | 48.55 | 37.14 5. 63 0.5 13.85 | 55.6 26. 61 4. 43 | 0.0
December. 29-6 0... 13.93 | 48.79 | 40.18 1.87 -20 | 20.02} 33.68 | 39.55 6.73 | .0
JANUALY. esos 12.26 | 38.30] 40.89 7.58 -95 9.44 | 46.72) 35.31 Soe, | -0
HEDTUALY oe kas oe 2.60 | 32.28 | 47.07 14. 66 2.38 2.58 | 21.46 | 48.90} 18.77 | 8.3
Marche som (4252.5: -25 25.89 | 52.64 17.39 3.81 -6 9.7 50.6 33.4 5.65
Je\j 0) il Le iss eee 1.16 20. 91 50.80 | 25.51 1.60 -0 17.0 58.57 | 20.36 4.33
Entire season. 6.68 | 34.82 | 45.07 11.80 1.62 | 6.92 | 29.86 | 44.74 15. 24 3:25

The data in Table 1 are based upon the sale of 128,487 boxes of
oranges and 31,479 boxes of grapefruit. In the second method for
determining the percentage of fruit shipped to New York City in
the various grades, the fruit was placed in only three grades instead
of five. The fruit was classified by the same method used for Table
1, except that fruit marked “fancy” and “ No. 1” was placed in the
first grade, and all “plain,” fourth and fifth grade fruit was left
out. The results, based upon a study of the auction sales, including
400,806 boxes of oranges and 126,193 boxes of grapefruit, showed
that the percentages of fruit in the three grades were 35.56, 44.33,
and 20.10 for oranges, and 34.43, 45.61, and 20 for grapefruit.

These data and those of Table 1 show that the two methods for
determining the grades shipped give about the same results. The
better grades are shipped during November and December; the
poorer grades, toward the close of the season. To a considerable
extent this due to the demand of the holiday trade, which calls for
the best fruit obtainable. This demand causes such a keen competi-
tion among packers that it is difficult for any but the better grades
to find a market until after Christmas.

Since the fruit sold in New York City grades much higher than
that sold in other markets, and, in fact, better than the average fruit
of the State, the percentages of the different grades of fruit of this
market and those of other markets must be compared, in order to
arrive at a just conclusion as to the amount of fruit in the different
grades shipped from the entire State. Such a comparison of grades
sold in New York City and other markets, including Baltimore,
Boston, Chicago, Cleveland, Philadelphia, Pittsburgh, and St. Louis,
is made in Table 2.

f

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6 BULLETIN 645, U. S. DEPARTMENT OF AGRICULTURE.
TABLE 2.—Vlercentages of various grades of oranges and grapefruit shipped

from Florida to New York City and other markets during the season of
1915-16.

Oranges. Grapefruit.
Market. i

First |Second} Third | Total First |Second| Third | Total

grade. | grade. | grade. | boxes. | grade. | grade. | grade. | boxes.
New. Mork Gityeseccen ack eee 35.56 | 44.33 | 20.10 | 868,541 | 34.43] 45.61] 20.00 272, 621
Other mankatsseeece ea soe eee 8.30 | 44.57] 47.13 |5,096,817] 885] 36.2 | 54.9 | 1,544,929

Totals and weighted per-
CONtages arte sete cera ces 12.39 | 44.53 | 43.08 |5,965,358 | 12.67 | 37.62 49.69 | 1,817,550
|

Taking into consideration all sources of information regarding.
oranges and grapefruit shipped out of Florida, the conclusion is
reached that for the purpose of this bulletin the percentages of fruit
in the first, second, and third grades approximate 13, 41, and 46,
respectively.

\

RAISING THE GRADE OF FRUIT BY SPRAYING.

Since by no means all Florida fruit is graded so well as that
shipped to New York, the problem of raising the standard is an im-
portant one. Is it worth while? Will it pay? From the results of
work in Florida it may be asserted confidently that it is worth while
and that it will pay in a very large number of Florida groves. Table
3 gives the percentages of the grades of fruit shipped from the same
erove during 1914, 1915, 1916 and during 1917, up to January 15.
In 1914 the small amount of spraying done came too late to prevent
blemishes caused by rust mites. In 1915 and 1917 the spraying was
done at the proper time, but in 1916 the application was made a little
too late to produce the best results. The data resulting from this
experimental work are so striking that comment is unnecessary.

TABLE 38.—Result of spraying upon the percentages of grapefruit in the various

grades.
2
Year and treatment.
1914 1915 1916 1917
Grade of fruit.
Sprayed
Not Well too late Well
sprayed. | sprayed. | for best | sprayed.
results.
Brits HU ee De SOL Fe Oe ees are OSA ae er 2.7 34.3 15.8 33. 7
DECOM ce Ae PERE RN Seb Aas Aa ae ae ears a eat 15.8 Slap 51.6 46.3
Gl Mot ogg Seen eg MR oe a os Ge APS RUC Son cinson os toot seat 50.0 10. 2 17.3 14.2
Botirth: [S509 Pee ee Oe ear a eles Sek eee eran ee ae see 31.5 3.7 15.3 5.9

In a second grapefruit grove during the season of 1913-14, when
no spraying was done, the percentages of fruit in the four grades
ran 0, 18.8, 65.5, and 20.8, respectively. During the season of 1914-15

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 7

the fruit from the same trees after having been sprayed ran for the
same grades 12.4, 73.1, 14.5 and 0 per cent, respectively. These data,
presented by Mr. S. F. Poole before the Florida Horticultural So-
ciety, show that spraying raised the percentages of fruit in the
first two grades from about 14 to 85.5 per cent, while the same treat-
ment lowered the percentage in the inferior third and fourth grades
from 86.37 to 14.5 per cent and raised all fruit above the fourth grade.

In a third grove the grapefruit of the season of 1913-14, which
had developed without protection by spraying, gave 0.6, 24, 59,
and 16.4 per cent, respectively, in the four grades. The same trees,
properly sprayed during 1914, yielded fruits during the 1914-15
season which graded for the same grades 27.4, 67.5, 5, and 0 per
cent, respectively. In other words, spraying increased the amount of
fruit in the first two grades from 24.6 to 94.9 per cent and reduced
that in the lower grades from 75.4 to 5 per cent; increased the first
grade from 0.6 to 27.4 per cent and reduced the fourth grade from
16.4 per cent to zero. The fruit in the two groves upon which data
have been given were graded by the Winter Haven Citrus Growers’
Association, and the spraying was done under the direction of Mr. S.
F. Poole, of Winter Haven.

The foregoing data, secured in the same grove two or more years in
succession, may raise the question whether the relative abundance
of pests, or more favorable climatic conditions, may not have been
an important factor in the better crops secured after spraying.
Without discussing this point at length the data secured in various
groves are given below:

Grove 1.—During 1913, 900 boxes of fruit picked from unsprayed
orange trees in the community graded 32.6 per cent “bright” and
67.3 per cent “russet,’” while 914 boxes picked from a sprayed grove
and apparently equally well cared for in other respects graded 90.4
per cent “bright ” and 9.5 per cent “ russet.”

Grove 2.—In the Hill grove at Winter Haven, which was sprayed
during 1914, the oranges shipped 60 per cent first, 35 per cent second,
and 5 per cent third grade; and the grapefruit, 30 per cent first,
67 per cent second, and 3 per cent third grade. The general run of
fruit grown in the same vicinity, upon trees in the same general state
of culture except that many had not been sprayed at all and others
sprayed only indifferently, and packed by the same packing house,
may be taken as a fairly good index to the grade of fruit produced
during the same season. This fruit shipped 10 per cent first, 62
per cent second, and 28 per cent third.

Grove 3.—In this grapefruit grove one block of trees was sprayed,
a second block was left unsprayed after June, while a third block
was kept as a check. Aside from spraying, the trees received practi-

1Florida Horticultural Society Report, 1915, pp. 130-132.

8 BULLETIN 645, U. S. DEPARTMENT OF AGRICULTURE.

cally the same treatment as regards cultivation and fertilization.
The fruit in the sprayed and unsprayed blocks grew on trees about
30 feet apart, or in adjoining rows, and was picked and packed
on the same day. The carload of sprayed fruit shipped 87.4 per
cent first and second and 12.6 per cent third and fourth grades;
the unsprayed carload shipped no first, 3.8 per cent second, and 96.6
per cent third and fourth grades. A more striking example of what
a maximum infestation of rust mites will do and the benefits derived
from spraying can scarcely be conceived. The carload of fruit left
unsprayed after June shipped 80.3 per cent first and second and 19.6
per cent third and fourth grades, thus indicating that if rust mites
are controlled thoroughly until the 1st of July on grapefruit little
damage will result. In other groves russeting has been observed in
January and February.

Grove 4.—In this grapefruit grove, 1 mile distant from grove 3,
sprayed and unsprayed fruit was grown during 1914 in adjoining
rows. The fruit from the sprayed trees shipped 18.8, 58.1, 15.1, and
7.9 per cent, respectively, in the four grades known as “ fancy,”
“bright,” “russet,” and “plain.” The fruits from the unsprayed
trees shipped 6,6, 43.6, 49.7 and 6 per cent, respectively, in the same
four grades. The percentage of second grade, or “bright,” fruit
from the unsprayed trees is much greater than from unsprayed trees
of grove 3, since the rust mites did not do so much damage in this
grove. It will be noticed that 15.1 per cent of the fruit from sprayed
trees was russeted, whereas 49.7 per cent was russeted on the un-
sprayed trees. In grove 4 the poorer results were due to the inefli-
ciency of the spray solution.

The foregoing data, under the general head of grades of fruit,
should convince any grower that it is possible to raise the grade
of fruit by killing pests so that the fruit will grade at least 35 per
cent first, 50 per cent second, and 15 per cent third, instead of the
present average for the State, which is 13 per cent first, 41 per cent
second, and 46 per cent third. Fruit usually will grow to a remark-
able state of perfection on healthy trees if only the insects and mites
are controlled. One grove, the fruit of which was packed by an asso-
ciation noted for its high-class work, produced 90 per cent “ Blue,”
or A No. 1 grade. The writer has seen 120,000 boxes of grapefruit
from sprayed trees that graded 60 per cent first and 25 per cent
second.

REDUCTION IN SIZE CAUSED BY INSECTS.

Insects and mites not only lower the grades of the fruit by the
blemishes they cause, but reduce the size to a considerable extent.
In raising the grades of the fruit by spraying, large benefits are
obtained in preventing the pests from reducing the size. In com-
mercial grading it is very difficult to show the difference in size of

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 9

oranges that have been damaged by mites and those that have not,
since in commercial houses all large, coarse fruits, as well as more
or less fruit that is inferior, are always placed in the second or third
grades with the “russets.” This reduction in size is so great, how-
ever, that even in commercial grading the difference in size in the
respective grades is considerable. Thus, in 941 boxes of oranges
of the first grade, 7,111 boxes of the second, and 3,376 boxes of the
third there were, on an average, 184.2, 197.9, and 200.4 oranges per
box; a difference of 7 per cent in the number of fruits per box in the
first and second grades, and of 8.8 per cent of those in the first and
third grades.

The difference in size of the fruit of the various grades ranges
from 4 to 14 per cent. In one community the general run of “ bright ”
fruit (unaffected by mites) averaged 203.8 oranges per box, and the
russeted fruit 222.2, or a difference of 9.28 per cent in favor of un-
affected fruit. In another near-by grove that was sprayed the
“bright ” fruit averaged 214 and the “russets” 228 fruits per box,
which is a difference of 6.6 per cent.

The number of grapefruit in 360 first, 970 second, and 279 third-
grade boxes of fruit averaged 53.2, 57.5, and 51.9, respectively. In
this instance the difference in number of fruits per box in the first
and second grades is 8.2 per cent. Undoubtedly so many large,
coarse fruits were placed in the third grade that these made the
average number of fruits per box less than even in the first grade.

It is much better, however, to make comparison of fruit of the
same variety from the same grove, and data are given here for this
purpose. Table 4 shows the numbers of grapefruit per box for the
various grades in a car of sprayed and of unsprayed fruit and of
fruit which was not sprayed after June. These are the same car-
loads of fruit referred to on page 7, grove 3.

TaBLe 4.—Numober of grapefruit per box from trees sprayed and unsprayed and
from trees unsprayed after June.

Number of grapefruit per box.

Grade. Not Re

xe spraye fe)
Sprayed.| “after | sprayed.

June.

1. TO aoa peooe ReBEse COED OC OCOD BEBE Be See Soo Bc Cae SEED ora 42.2 46.6 0.0
Su. LBSTSTED amg esi ta i RA a NT PRS ee 43.6 49.7 48.4
BL, JERE a rae Bee eae en SOO a ea a Le EERE RO Rene is Us at Beer | 45.2 52.3 49.3
Mh TIE ee eee a eee ee cca Senn eC Sor Eon o re Scene on cocce ppm: supe Coo sare | 38.8 43.2 46.1
(OLS Ti Cor Ler ay gts See ee ee secre 4 uC Sane ode: ¢ aes See cennctee 42.8 49.0 49.1

It will be seen that the sprayed fruit averaged 42.8 and the un-
sprayed fruit 49.1 fruits per box. This difference may not appear to
be very great at first sight, but if the unsprayed fruit had been as

21698°—18—Bull. 645—2.

10 BULLETIN 645, U. S. DEPARTMENT OF AGRICULTURE.

large as the sprayed, there would have been 344.1 boxes of fruit in-
stead of 300, or again of 14.7 per cent. The “russet” grade is smaller
in all cars than either the “fancy” or “bright.” All large, coarse
fruits, were packed in the “ plain,” although they might be classed as
“brights.” Table 4, although it contains the data given by a com-
mercial concern, does not indicate as great a difference as really
existed. On the unsprayed trees there were many fruits so small and
of such poor quality that they were never sent through the packing
house.

Grapefruit grown about 1 mile from that discussed in Table 4 was
sprayed with a different material, soda-sulphur. The sprayed and
unsprayed fruit was picked on the same day. The number of fruits
per box from the sprayed trees averaged, for the same grades given in
Table 4, 47.8, 51.7, 56, and 53.4 per box, respectively ; from the un-
sprayed trees, 52.3, 56.7, 59.5, and 0, respectively. The “russet”
fruit in both cases was much smaller than any of the other grades.
Taken as a whole, the fruit from the sprayed and unsprayed trees
averaged 51.5 and 57.8 fruits per box, respectively, which gives a
percentage difference of 12.3 in the number of fruits in favor of
spraying. In another instance grapefruit from sprayed trees aver-
aged 50.2 fruits per box as compared with 57.8 fruits from un-
sprayed trees in adjoining rows; a difference of 15.2 per cent in
favor of sprayed fruits.

The reduction in size following rust-mite attack accounts, to a
certain extent, for the small number of boxes produced in 1911, when
practically all the unsprayed citrus fruit was “russet,” and about
half was “ black russet,” or about two sizes smaller than it would have
been had it not been affected by rust mites. One test shows that 66
sprayed fruits filled the same box as 99 unsprayed fruits picked from
an adjoining row, or a difference of 334 per cent. From orange trees
sprayed with lime-sulphur, 1-25, April 22, 1911, 338 fruits averaged
3.29 inches in diameter. The skin of this fruit was smooth and the
texture good. From unsprayed adjoining orange trees 1,234 fruits
averaged 2.58 inches. It would require 112 of the former to fill the
average orange box and 226 of the latter, or twice as many.

The reduction in size in also shown by the average weight of the
fruit. In a miscellaneous lot of oranges, graded commercially, 575
“brights” weighed 241 pounds and 575 “russets” weighed 2254
pounds, which made a difference of 64 per cent. This fruit, of
course, had been picked at the same time and from the same grove
and the collection represented all the different sizes. The fruit had
not received any spraying. In another lot, 75 “bright” grapefruit
which had been sprayed thoroughly throughout the season weighed
99.75 pounds, and 75 fruits which had received no spraying through-
out the year weighed 88 pounds, which makes a difference of 11.77

per cent. '

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 11

The foregoing data show that the loss resulting from the reduction
in size of the fruit is close to 12.5 per cent, or about one size. About
half the citrus crop of Florida suffers this loss. The data also con-
firm the observations made on the size of “ brights” and “russets ”
when packed. When fruit is graded in a packing house and then
run through the sizer the full bin on the “bright” side is invariably
one size larger than the full bin on the “russet” side. These facts
also substantiate the statement of Mr. S. O. Chase, of Sanford, Fla.,
who figured out more than 25 years ago that the increase in
size which results from spraying pays for the cost of spraying.
They also confirm the statements of Mr. F. D. Waite, of Palmetto,
and Mr. A. B. Harrington, of Winter Haven, that rust mites reduce
the size about 124 per cent.

The belief is general in Florida that “ russet”’ fruit will ship bet-
ter, or with less decay, than “bright” fruit. If this is the case it is
possible that the supposedly superior shipping qualities of the “ rus-
set” fruit might outweigh any advantages which the “bright” fruit
might possess. While the data given in the following paragraphs
may not be entirely conclusive, they certainly show that bright fruit,
which retains its natural “waxy” coating for protection, ships
equally as well or better than “russet ” fruit, or fruit that has been
injured by rust mites to the extent of losing its normal protection.

Test 1: Grapefruit—On January 30, 24 brights and 24 russets were
picked and placed in the laboratory. These were examined from
time to time, and on April 7 463 per cent of the bright fruit had
decayed and 584 per cent of the russets.

Test 2: Fifty-one grapefruit each, of brights and russets, were
picked on the same day as the preceding and placed in the laboratory.
On April 7, 49 per cent of the brights had decayed and 75} per cent
of the russets.

Test 3: Oranges—One box of bright oranges and one box of russet
oranges, each containing 200 fruits, were purchased at the packing
house on March 9. These fruits were picked from the same grove.
On April 7 the bright oranges showed 48} per cent decay and the
russet oranges 59 per cent.

Test 4: One box of brights and one box of russets containing 160
oranges each were set aside March 9. On April 7, 29.3 per cent of
the bright fruit had rotted and 30.6 per cent of the russets.

Test 5: One box each of brights and russets, containing 150 oranges
each, were used on March 3. On April 7, 56 per cent of the bright
fruit had decayed and 66 per cent of the russet.

Test 6: One-half box each of brights and russets were put under
observation on March 3. On April 7, 54 per cent of the brights had
rotted and 74 per cent of the russets.

12 BULLETIN 645, U. S. DEPARTMENT OF AGRICULTURE.

In the spring of 1917 another series of experiments was conducted
to determine the relative merits of bright and russet fruit with refer-
ence to their carrying qualities. ’welve lots of oranges, each con-
taining an equal number of brights and russets, were picked and
carefully selected so as to avoid any mechanical injuries. So far as
possible, the brights and russets from each lot were taken from the
same tree. Examinations were usually made every seven days. Table
5 gives the percentage of decay for each period of all the lots.

TasLE 5.—Percentage of decay of “ brights” and “ russets.”

“*Brights.’’ ““ Russets.”’
a |
Number Total Total
of lays. Number Nunes number Per Ranier Shuniber number Por
sound | decayed ¥ cen sound | decayed cent
fruits. fruits. oe decay fruits. fruits. pci decay.
95 0 0 | 0.0 95 0 0 0.0
94 1 1 1.05 95 0) 0 -0
12 93 i! 2 2.10 95 0 0 -0
19 89 4 6 6.31 87 8 8 8. 42
26 79 10 16 16. 84 78 9 iy 17.90
33 71 8 24 25. 26 56 22 39 41.05
40 60 ii 35 36.8 40 16 55 57.90
47 59 1 36 37. 89 31 9 67.36
54 50 9 45 47.36 12 19 83 87. 36
61 34 4 49 | 51.57 ll 1 84 88. 42

The above experiment was terminated about 2} months after it
was started. At that time 27 of the bright fruits were sound, 25
of which were eaten, and only 3 of the russets were sound, none
of which were edible. The 95 bright fruits had averaged 51 days and
the 95 russet had averaged 36 days before developing decay. In 11
of the 12 lots the brights lasted longer than the russets. According
to weight, the percentage of decay was 45.3 in the brights and 64.5
in the russets.

The rate of evaporation of the juices is also much greater in
russet fruit than in bright. From January 30 to April 7, 1915, 24
bright grapefruit lost 4.7 per cent and 24 russet lost 13.6 per cent
from evaporation. During the same time 51 bright grapefruit lost
5.9 per cent, and the 51 russet lost 9.5 per cent. One box of bright
oranges lost 10.4 per cent, and another box of russets containing the
same number of fruits lost 15 per cent. Another box of brights lost
14.8 per cent by evaporation and the box of russets lost 17.9 per cent.
In one box of half brights and half russets the brights lost 17.4 per
cent and the russets 21 per cent. In one box of brights the loss from
evaporation was the same as that sustained by the russet box. In 8
of the 12 lots mentioned under “ decay ” (Table 5) the percentage of
evaporation was greater from russet than from bright fruit and the
total of the 12 lots showed the russets evaporated 23.12 per cent and
the bright 22.68 per cent.

ia <

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 13

\

There seems to be an impression among consumers and retail
dealers that russet fruit is a variety of citrus instead of being the
result of the former presence of thousands of rust mites. The re-
sponsibility for this erroneous idea rests with the salesman. It is
considered good salesmanship to sell what goods there are on hand
and to convince the purchaser of the merits of the same. Since more
than half the crop is russet, some explanation must be made to the
consumer as to the quality of the fruit he purchases. The explana-
tion that russet fruit is a variety fulfills all the requirements of good
salesmanship. The necessity for this exercise of shrewd salesman-
ship, as well as its continuation, rests with the Florida citrus grower.

One also hears frequently in Florida that russet fruit is sweeter
than bright. So far as is known, no analyses indicate that such isthe
ease. Since the russet fruit is not sold before the holidays, it has
ample opportunity fully to ripen, so no russet fruit is ever sour. In
some tests made March 25, 1914, several russet and bright oranges
were peeled so that they could not be told apart by the taster. These
were given to a person to taste. In both cases where bright and
russet fruit were compared, the person pronounced that the bright
was the sweeter. On January 29, 1915, five men pronounced sprayed
fruit sweeter and possessed of a greater refinement and delicacy of
flavor than unsprayed fruit from adjoining rows.

BETTER GRADES OF FRUIT BRING BETTER PRICES.

Obviously it is useless to raise the grade of fruit if second and
third grade fruit sell for as much as the first grade. There is no
reason to spend money to make first-grade fruit unless the improved
fruit brings a good yield on the investment required to produce it.

In order to show the difference in price received for different
grades of fruit Tables 6 and 7 have been prepared. The data of
Table 6 are based upon the returns from the 128,487 boxes of oranges
and the 31,479 boxes of grapefruit, and these data are given in
Table 1.

TABLE 6.—Difference in the price received in the New York market for different
grades of oranges and grapefruit during the season of 1915-16.

Difference in price received between the grades of—

Oranges. Grapefruit. |
Month.
First |Second| Third | Fourth First |Second| Third | Fourth
and | and | and | and ee and | and | and | and oe
second | third | fourth | fifth | “fice. |Second| third | fourth | fifth ELS
grade. | grade. | grade. } grade. * | grade. | grade. | grade. | grade. ates)
November. ......... $0.39 | $0.28 |—$0.01 | $0.39 | $1.06 | $0.66] $0.36] $0.29] $0.00 $1.30
December......:.... .O7 08 .09 - 05 79 -55 57 - 26 OOS 136
WANUSIVR te ssctees ese 23 14} —.00 Ac Y/ 74 37 36 34 00 1.08
MG DNUALY: xo tao a'sicictein 73 14 14 aay) 1.38 68 25 25 03 1.21
TGR: oee sees 3 1.36 | —.09 | —.16 -49 1.59 2. 22 43 47 229 11.20
ADEUSe- paces ocncs 96 14 06 67 1.82 00 18 17 25 60

1 Difference between second and fifth grades; first grade is unusual sale.

,
f
¢
7

7

14 BULLETIN 645, U. S. DEPARTMENT OF AGRICULTURE.

The dash (—) placed before the difference in price indicates that
a lower grade sold for more than the next higher grade. This oc-
curred several times among the grades of oranges, but not among
those of grapefruit. The only explanation that can be offered for
this irregularity is that the lower grades had the sizes desired by
the trade at the particular time of the sale.

Table 7 shows the differences in price for the grades of 400,805
boxes of oranges and 126,193 boxes of grapefruit when these are
divided into three instead of five grades.

TABLE 7.—Differences in the price receved in the New York market for different
grades of oranges and grapefruit during the season of 1915-16.

Difference in price received between the grades of—

Oranges. Grapefruit.
Month. |
Firstand| Second | Firstand | Rirstand| Second | Firstand
second jandthird| third second jandthird| third
grades. | grades. | grades. | grades. | grades. | grades.
November vase Of. 2 eee eee eee $0. 342 $0. 044 $0. 385 $0. 517 | ~ $0.314 $0. 831
Wecemberee te seek epee ee Sere eek a ae ae - 243 . 136 -379 . 369 . 654 1. 023
January o see sees . 221 ali . 338 SPRY) . 362 . 599
HEDLUADY2 = see eee . 168 . 114 . 282 .378 -325 - 703
Manche cles gue 099 054 . 045 295 569 . 864
eX 0) ll (Ee ee Aenea eatin VERN TN a Se 226 110 . 336 0.59 279 338

If the difference in price received for the first and third grades be
added and the sum be divided by the number of months, an average
difference of 30 cents in price received for the oranges and 72 cents
for the grapefruit is obtained. In a miscellaneous lot of 5,427 boxes
of fruit, the first grade averaged 48.8 cents more than did the second
grade, and the second averaged 8.3 cents more than did the third
grade.

Opportunity is seldom presented for comparing the price of
sprayed and unsprayed fruit from the same grove. Through the
cooperation of Mr. J. A. Stevens, of De Land, this was done with
two carloads of grapefruit shipped in 1914 from sprayed and un-
sprayed trees, that were picked and packed on the same day and
sold in the same market. The sprayed fruit sold for $1.94 per box;
the unsprayed fruit for $1.69. These respective prices are disap-
pointing. It had been anticipated that there would be at least a
difference of 75 cents instead of 25 cents in favor of the sprayed
fruit. The net profits due to spraying, however, were sufficient to
pay one-fourth of the freight charges. Although the difference is
slight, it is more than four times what it cost to spray the trees. The
prices of the respective grades of the fruit could not be obtained.

In a grove about 1 mile distant from the grove previously men-
tioned 516 and 300 boxes of grapefruit, respectively, were picked from

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 15

sprayed and unsprayed trees in adjoining rows. It is not known
whether all the fruit was sold in the same market. The sprayed
fruit brought 98 cents per box, the unsprayed fruit 85 cents per box.
The difference in price, though small, was twice the cost of spraying.
Because of the vagaries of the market, due to the daily fluctuation
in supply and demand, it can not be stated that the better grades
will always bring the better price, yet the data presented leave
no doubt that spraying raises the grade of the fruit and largely over-
comes the devitalized effect caused by insects, and that, other things
being equal, the better grades bring better prices.

SPRAYING SCHEME FOR CONTROLLING CITRUS PESTS.

As a general proposition the time to spray for the control of all
pests of citrus trees is when they are present in such numbers that, if
left to reproduce without artificial hindrance, they would soon become
injurious. In other words the pests should be killed before they can
do much damage to either the tree or the fruit. The pests should
always be kept in such a state of repression that they can do little
or no damage. In case the various pests of citrus are permitted to
become so abundant as to cause injury, the profits which may be ex-
pected from artificial treatment, such as spraying with an insecticide,
are, to a certain extent, lost. Fortunately the life history and habits
of nearly all citrus pests are such that good results can be obtained at
any time of the year when the spray is applied. Nevertheless there
are times when spraying is more opportune than at others. These
periods come when the largest number of the insects are very young,
for then they are killed most easily.

The following spray scheme has been used very extensively for
four summers in Florida and generally has given satisfactory re-
sults. It must be admitted, however, that no hard and fast scheme
can be recommended, and that to a large extent the number of
sprayings depends on the thoroughness of the work.

I. Paraffin-oil emulsion; Government formula, 1-66 or 1 per cent
of oil. May—The main object of spraying at this time is to kill
white flies, scale insects, and, to a large extent, rust mites. This
treatment, however, must not be relied upon to control rust mites.
The spraying should be done after the adults of the first brood of
white flies have disappeared and before the appearance of those of
the second brood. The fruit should be an inch or more in diameter.
Since this treatment is given before the beginning of the rainy season,
it does not interfere with the work of the beneficial fungi in reducing
those insects not killed by the spray.

Il. Lime-sulphur solution, 32° Baumé, 1-50 to 1-75. June to
July.—The main object of this treatment is to kill rust mites, and the

16 BULLETIN 645, U. S. DEPARTMENT OF AGRICULTURE.

correct time for its application varies with the appearance of the
maximum number of the rust mites. It should be applied before the
mites get very abundant and before any russeting appears. It will
also kill some scales and white flies, but is not of great value for
that purpose.

Ill. Paraffin-oil emulsion; Government formula 1-66, or 1 per
cent of oil. August 25 to October 31.—This is the second spraying
for white flies and scale insects. The object of spraying at this time is
to kill the white-fly larvee which are the progeny of the third and
last brood. It is this brood that causes nearly all the damage from
the white flies, and the earlier they are killed the better it is for the
trees. This spraying also will remove the sooty mold from the trees
and a sufficient amount from the fruit to permit the fruit to be col-
ored up by the sun. Soda-sulphur, 1-50, may be added to this spray-
ing to increase its effectiveness in killing rust mites.

IV. Lime-sulphur solution, 32° Baumé, 1-50 to 1-75. November
or December.—The object of this spraying is to kill rust mites, and
it may or may not be necessary, depending on the abundance of the
mites.

It may be necessary to spray for rust mites before Treatment I
is given. This is especially the case with grapefruit in the more
southern counties. In case the red spider becomes abundant enough
to cause injury, an application of lime-sulphur solution should be
given. In case of heavy scale-insect infestation it may be necessary
to spray three times with the oil sprays, in which case the treatment
can be given in midsummer or in winter. If the red scale is very
abundant, two sprayings with the oil emulsions should be given at
intervals of about a month.

The paraffin-oil emulsion may be made according to directions
given in Circular No. 168, Bureau of Entomology.

In addition to the foregoing there are three highly satisfactory
miscible-oil sprays on the market in Florida.

The soda-sulphur solution is made according to the standard
formula: 30 pounds of sulphur, 20 pounds of caustic soda, and 20
gallons of water. This tests about 16° Baumé and may be used 1-40
instead of lime-sulphur solution, but it is not so effective in control-
ling rust mites. It has an advantage over lime-sulphur solution in
that it mixes readily with the oil emulsions.?

COST OF SPRAYING.

The cost of spraying depends upon many different factors, such as
the size of the trees, nearness to water, convenience of operation,
type of spraying outfit employed, insecticide used, and character of

1Mor directions for making lime-sulphur solution see Farmers’ Bulletin 908.

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. ay)

the labor. No grower should expect to spray a bearing tree for less
than 3 cents for each application. It would be better to place the
minimum at 4 cents. It should not require more than 10 cents to
spray the largest trees in the State if any considerable number are
present in one grove. An average cost per tree should not exceed 5
to 6 cents. If one figures the cost per box, a minimum would be 1
cent per application for oi] spray and somewhat less for lime-sulphur.
A maximum would be 14 cents for either insecticide. An expenditure
of more than 6 cents per box for the entire year should be unnecessary.

PROFITS AND BENEFITS.

It is impossible to express accurately the percentage of profit to be
expected from spraying to control pests on citrus. The same condi-
tion applies to cultural and other grove operations in Florida. The
data at hand are sufficiently accurate, however, to be worth pre-
senting.

It has been shown that the better grades bring more money than
the lower, yet it would be fallacious to assume that if the entire crop
were of a high grade the grower would receive correspondingly
higher prices. The trade will consume only so much high-grade fruit.
It is reasonably certain, however, that the Florida crop has not yet
reached the high standard where it would be no longer profitable to
produce more high-grade fruit. |

At present 13 per cent first, 41 per cent second, and 46 per cent
third grade oranges are shipped from, the State, and it is possible
and practicable to raise this standard to 35, 50, and 15 per cent for
first, second, and third grades, respectively. It is assumed that the
trade would handle fruit of this quality. Thus, the first grade is
increased 22 per cent and the second 9 per cent. If 7,600,000 boxes
are taken as the basis for the crop of 1915-16, there would be
1,273,987 boxes more in the first grade if spraying were done. These

would sell, according to Table 7 (oranges) for 21.6 centst more per
box, or an increase of $275,181. There would also be 9 per cent more
second grade, or 521,177 boxes. These would sell for 9.6 cents more,
or an increase of $50,033.

The percentage of the various grades of grapefruit was not very
different from that of the oranges, so 13, 41, and 46 per cent may be
used to represent the first, second, and third grades of grapefruit,
respectively. The standard for grapefruit also can be raised to grade
35, 50, and 15 per cent. There would then be 22 per cent, or 399,685
boxes, which would sell for 30.9 cents per box more, an increase
of $123,559. There would be 9 per cent, or 163,508 boxes, which would

1New York City prices. Other prices could not be obtained.

18 BULLETIN 645, U. S. DEPARTMENT OF AGRICULTURE.

sell, according to Table 7 (grapefruit), for 41.7 cents more per box,
or an increase of $61,182.

The total increase in value by raising.the grade would be $509,955
for the entire crop of oranges and grapefruit.

Elsewhere in this bulletin it has been shown that “ russet” fruit is
of about one size, or about 12.5 per cent smaller than normal fruit.
If it is estimated that one-half of the crop is “russet” there would
be a reduction of 475,000 boxes, which, valued at $1, would produce
a loss of $475,000. This is extremely conservative. As a matter of
fact, 100,000 boxes of fruit in Florida are thrown away because the
fruit is too small!

In regard to the reduction in yield caused by the devitalization of
the trees, it is very conservative to estimate this at 10 per cent, or
760,000 boxes. In reality it is probably 20 to 25 per cent, and many
sprayed groves prove this to be true, but for this estimate it is placed
at 10 per cent. This amount of fruit is valued at, $760,000.

This would make a total of $1,744,955 as a minimum estimate for
the increase that could be expected from spraying the entire crop.
The cost of spraying groves producing 7,600,000 boxes would be not
more than 6 cents per box, or $456,000. This would be a net gain of
$1,288,955 in the value of the crop produced. This gain could be
divided in half and still a handsome profit would follow spraying.

Tn addition to the direct profit, there is the satisfaction, which every
enthusiastic orange grower must feel, in maintaining healthy trees
and producing high-grade fruit.

CONCLUSION.

Of the total damage caused by insects and mites to citrus in
Florida, more than 95 per cent may be attributed to six species.
These, in the order of their destructiveness, are the citrus white fly,
the purple scale, the rust mite, the red scale, the cloudy-winged
white fly, and the red spider.

Aside from the satisfaction of growing fine fruit and owning:
healthy trees, it is estimated from the data reported in this bulletin
that had the 1915-16 crop of oranges and grapefruit been sprayed
according to the schedule recommended, the growers of Florida
would have increased their net returns by $1,288,955.

There is no reason- why the standard percentage of fruit in the
higher grades can not be raised so that the percentage in the first,
second, and third grades will be 35, 50, and 15 instead of, as at pres-
ent, 13, 41, and 46. In one of several instances given, spraying in-
creased the amount of fruit in the first and second grades from 24.6
to 94.9 per cent, and reduced that in the third and fourth from 75.4

F
‘
F

SPRAYING TO CONTROL ENEMIES OF CITRUS TREES. 19

to 5 per cent; increased the amount in the first grade from 0.6 to
27.4 per cent, and reduced that in the fourth from 16.4 per cent to
zero.

The better prices which, in most instances, can be obtained for
the better prades of fruit fully warrant the adoption of a spray sys-
tem that improves the grade and the amount of fruit produced.
The data presented leave no doubt as to the practicability of making
such improvement in the Florida citrus crop if the grower will ad-
here to the spray schedule outhned.

= 3

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WASHINGTON : GOVERNMENT PRINTING OFFICE : 1917