Control of dried-fruit insects in California

Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

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BULLETIN OF, THE

USDEPARIMENT OF AGRICULTURE &

Pan anes 7
No. 235 < >

Si

Contribution from the Bureau of Entomology, L. O. Howarth Chiel
June 24, 1915. Pe

CONTROL OF DRIED-FRUIT INSECTS IN CALI-
FORNIA.'

By

Wiuu1am B. Parker,? Entomological Assistant, Truck-Crop and Stored-Product Insect
Investigations.

INTRODUCTION.

The State of California is especially adapted to the raising of fruits.
It is manifest that only a part of the great crop which is annually
produced may be marketed in a fresh condition, since it is impossible
to preserve semitropical and other soft fruits for more than a very
limited time in the fresh state. The fruit canneries and the dried-
fruit industry have accordingly been formed with a view to the utiliza-
tion of the surplus fruit and have assumed large proportions, the
production of dried fruits for the State of California being estimated
at 140,000 carloads annually.

The importance of this industry and the fact that numerous in-
quiries are made concerning the control of the insects which attack
dried fruits warrant investigation of the insect enemies of dried fruits
in California. ‘This was undertaken in a preliminary way in 1908, but
owing to lack of funds was discontinued until 1911, at which time the
writer, working under the direction of Dr. F. H. Chittenden, was
assigned to this project. The investigation has been continued to
the time of publication, and the preliminary notes are herewith sub-
mitted.

1 The observations in this bulletin and the data on life history and habits were obtained in central Cali-
fornia, the author having his headquarters at Sacramento, but it is probable that these particulars do not
differ materially in other fruit-growing sections of the United States, especially in the eastern and southern
fruit regions.

2 Resigned Aug. 31, 1914.

NotEe.—The writer has been assisted in this investigation by the Roeding Fig Packing Co., the Rosenberg
Co., Mr. D. L. Smith, of the Schuckl Co., the California Dried Fruit Exchange, the Robt. Gair Co., and
the Petterson Carton Wrapping & Sealing Machine Co., who by their cooperation have greatly facilitated
the prosecution of this project. He also wishes to acknowledge the assistance of Mr. R. E. Campoell, of the
Bureau of Entomology, who brought to completion some of the experiments detailed in this paper.

90548°—Bull, 235—15

2 BULLETIN 235, U. S. DEPARTMENT OF AGRICULTURE.
INSECTS CONCERNED IN THE INJURY.

During the progress of this investigation a study of the insect forms
most injurious to dried fruits in California has been pursued, with the
result that the follow-
ing species have been
collected, the more
important being con-
sidered later in sepa-
rate paragraphs.

The Indian-meal
moth (Plodia inter-
punctella Hibn.) (fig.
1) is probably the
Fic. 1.—The Indian-meal moth (Plodia interpunctella): a, Moth; most common and

b, chrysalis; c, caterpillar; d, head of same; e, first abdominal destructive of these
segment of same; /, caterpillar, dorsal view. a, b,c, /, Somewhat tap oS Nae :
pests, its large size

enlarged; d,¢, more enlarged. (From Chittenden.) i : :

2 making it particularly
conspicuous, while the nature of its attack renders infested fruit most
disgusting in appearance. (See Pl.I, figs. 1,2.) The fig moth (Ephes-
tia cautella Walk.) (fig. 2) is next in importance among the moths,
while a variety of
beetles, including the
dried-fruit beetle
(Carpophilus hemip-
terus. L.), the saw-
toothed grain beetle
(Silvanus surinamen- .
sis L.), the foreign
grain beetle (Cathar-
tus advena Waltl),
and a fungus beetle

(Henoticus serratus Fic. 2—The fig moth (Ephestia cautellz): c, Moth; b, denuded wing,
if. are nerally showing venation; c, larva, dorsal view; d, two egg mases. a,b,c,
Gy a oe tei Enlarged about four times; d, more enlarged. (From Chittenden.)

injurious. Twosugar
mites (T'yroglyphus siro Gerv. and T. longior Gerv.) are also fre-
quently found. The pomace flies (Drosophila ampelophila Loew)
attack only the sweet, watery fruits, or those that are fermenting, and
can hardly be considered as dried-fruit insects. Ants are occasion-
ally found in dried fruits, but do not breed therein, and can usually
be best attacked by destroying their nests outside the packing house.

ECONOMIC IMPORTANCE OF DRIED-FRUIT INSECTS.

The annual financial loss to all who handle dried fruits from the
Pacific coast would be very difficult to estimate, since these prod-
ucts are rapidly distributed by the packers over a large territory,

CONTROL OF DRIED-FRUIT INSECTS IN CALIFORNIA. 3

and the injury is first noticed by the retailer or the consumer.
Moreover, the retailer is inclined to be somewhat reticent regarding
the presence of wormy fruit in his establishment, although an exami-
nation frequently shows such to be the case. A few retail grocers
stated that the ‘‘worms” were especially troublesome during the
summer months, and while the majority of those interrogated ad-
mitted with reluctance that they ever received wormy fruit, it was,
no doubt, present in their stores at the time. Many companies
claimed that it would be difficult to secure the exact figures, but
admitted that they usually sold a considerable quantity as hog feed
during the season. A wholesale grocer stated that his annual loss
on dried fruits returned because of insect infestation was about $50,
but that the loss in 1912 approximated $150. These are only a few
individual instances, and the greatest aggregate loss is through small
quantities of infested fruit which are thrown away or sold as hog
feed, the retailer preferring the loss of a small quantity of fruit to the
trouble of returning it to the wholesaler. It is readily apparent,
however, that the annual loss must in the aggregate be considerable.

For the reason that no estimates can be made of the injuries by
- the Indian-meal moth to fruits in California, it is worth stating that
according to figures furnished by Dr. Chittenden in 1910, there was
a loss to the peanut industry, through the ravages of this species,
amounting to 20 per cent, or, at a conservative estimate, $3,000,000."

PRELIMINARY OBSERVATIONS.

Observations begun in 1911 in central California, with headquar-
ters at Sacramento, with special reference to insects attacking dried
figs, were soon extended to all dried-fruit insects. It was found that
in most cases insects were present in the field where the fruit is dried,
that they were quite numerous around the packing houses, and that
they were present in warehouses and stores in sufficient numbers to
threaten severe infestation to boxes of dried fruit that might be
stored there. There are usually one or more cracks or openings in
the boxes (PI. II, fig. 2) through which an insect or mite can readily
crawl. The paper used in lining the boxes does not to any extent
prevent their entrance.

These preliminary observations led to the conclusion that the
problem could not be successfully combated by attacking it at any
one point, but that the methods of drying, storing, processing,
packing, and shipping should be investigated.

THE INDIAN-MEAL MOTH.

The life history of the Indian-meal moth (Plodia interpunctella
Hiibn.) will vary with the prevailing temperature, but was deter-

1Popenoe, C. H. The Indian-meal Mothand ‘‘Weevil-cut ”’ PEELE: U.S. Dept. Agr., Bur. Ent.,
Cir. 142,6 p., 1 fig., Sept. 16,1912. See p. 1.

4 BULLETIN 235, U. S. DEPARTMENT OF AGRICULTURE,

mined at the Sacramento laboratory during June, July, and August,
1913, as follows: Egg stage, 6 days; larval stage, 35 days; pupal
stage, 12 days; adult, about 14 days. Total, from egg to adult, 53
days, or 1 month and 23 days. -

While the subject of this article is practical and-based on condi-
tions at Sacramento, Cal., it should be added that in the case of the
life history of this species Dr. Chittenden has pointed out ! that ‘‘ex-

periment shows that the insect is capable of passing through all its -

several stages from egg to adult in five weeks, which furnishes a pos-
sibility of six or more generations in a well-heated atmosphere,
although in a moderately cool granary or other storehouse four or five
broods is probably the normal number per annum.”

The sudden appearance of large numbers of larve in dried fruit
is readily explained by Table I, which shows the number of eggs
deposited by six moths which were Commied in the laboratory to
determine the rate of oviposition.

TaBLE I.—Egg-laying records of the Indian-meal moth.

Days
No | Total
ist 2d 3d 4th 5th. 6th 7th 8th
tae ee 46 79 36 23 24 16 1 pee (eae sees 235
Dre: 56 65 Bih 36 36 21 Gig caries 0
Sets 39 43 34 18 16 Oi oe | ree 156
Ares 16 33 47 64 45 56 12 13 286
Sieeee 59 51 55 38 26 Eien PRS ee 4 bees 234
Se a eae san Ee aie aT Bc ea |S ck wale mn ne | ae | Dc 168

1 The number of eggs in this vial was determined as total and not by days.
Average number of eggs deposited by the six moths, 221.3.

These eggs were deposited mostly during the night.

The life cycle during the summer, as given in a preceding para-
graph, is only 53 days. Starting with one fertile female in a packing
house on June 15 (provided all of the insects matured), there would
be 221 moths by the following August 15, and by August 30 (pro-
vided that half of these moths were females) there would be a total of
23,310 larve in the dried fruit.

Under natural conditions some of the eggs do not hatch and many
of the larve fail to mature, but from the foregoing data it is readily
understood that a few moths of this species are capable of producing
a very severe infestation within a relatively short time, provided that
temperature and other conditions are favorable.?

1 Chittenden, F. H. Some Insects Injurious to Stored Grain. U.S. Dept. Agr., Farmers’ Bul. 45, 24
p., 18 fig., 1897. See p. 10.

2 The hymenopterous parasite Habrobracon hebetor Say is frequently found attacking the larve of the
Indian-meal moth, but it has not been observed appreciably to affect the infestation in California.

PLATE |

ulture.

Ic

Dept. of Agri

S.

U

235,

Bu

MOTH ON A

Fic. 1.—THE INDIAN-MEAL MOTH (PLODIA INTERPUNCTELLA)

(ORIGINAL. )

DRIED APRICOT.

(ORIGINAL.)

LARVA ON A DRIED APRICOT.

Fia@. 2.—THE INDIAN-MEAL MoTH

IN CALIFORNIA.

INSECTS

DRIED FRUIT

Bul. 235, U. S. Dept. of Agriculture. PLATE II.

Fig. 1.—FiGS HANGING ON TREES DURING-THE WINTER CONTAINING HIBERNATING
ADULTS OF THE DRIED-FRUIT BEETLE (CARPOPHILUS HEMIPTERUS). (ORIGINAL.)

i Se ON m0

Fia. 3.—AN INFESTED Box OF FIGS
IN THE ORDINARY PACKING CASE.

Drie€p Fruit MAY BECOME INFESTED. (ORIGINAL. )
(ORIGINAL. )

Fia. 2.—THE AVERAGE PACKING Box,
SHOWING CRACKS THROUGH WHICH

es

CONTROL OF DRIED-FRUIT INSECTS IN CALIFORNIA. 5
HIBERNATION.

Partly grown larve brought into the laboratory October 10, 1913,
spent the winter in that stage, pupated in the early spring, and
emerged as adults April 16, 1914. Larva were observed at various
times during the winter in dried fruit and partly spun up in corners
and cracks of warehouses. Adults were not observed in warehouses
until April 15, when many were found to be emerging. In California
this insect appears to hibernate in the larval stage, pupate in the
early spring, and emerge as an adult about the middle of April.

THE DRIED-FRUIT BEETLE.

The dried-fruit beetle (Carpophilus hemipterus L.) is probably the
next in importance as a destructive dried-fruit insect. It is found in
large numbers in the figs before they drop from the trees and in bins
of figs and other dried fruits. The adults often frequent the packing
houses in large numbers, where they swarm over and deposit eggs on
the fruit which has been dipped and put out to cool. They breed
readily in the moisture of the dried fruits, but apparently can not live
in fruit that is moderately dry.

The adult insect hibernates in stored fruit in the packing houses,
in figs, and probably in other fruits which are not gathered from
the field at the time of harvest. Plate II, figure 1, shows figs which
were allowed to remain on the trees during the winter, and which were
later found to be highly infested with Carpophilus hemipterus.

On September 3, 1911, 5 pounds of dried figs, taken at random from
each of seven different dryers in the vicinity of Fresno, Cal., were
placed in boxes made insect-proof by plugging all cracks with cotton
and wrapping carefully in stout paper. When examined January 13,
1912, the fruit in three of the seven boxes was badly infested. The
results of this experiment prove that many figs are infested before
they are shipped to the packing house and that the drying sheds are
one of the sources of infestation. These conclusions will apply equally
well to other fruits. The processing may kill the insects in the fruit
at the time of processing but will not protect them from infestation
while they are being dried or held in the drying sheds prior to shipping
to the packing houses.

It has been found that infestation takes place in the field, in the
packing house, in the warehouse, and in the grocery store.

PROCESSING DRIED FRUIT.

Dried fruit from the bins of the packing house is usually quite dry
and not particularly attractive or appetizing in appearance. In order
to improve its texture so that it will pack well and be attractive to the
consumer, it is processed. In Table II will be found the formulas
for processing fruit that are in common use in California.

6 BULLETIN 235, U. S. DEPARTMENT OF AGRICULTURE.

Tasie Il.—Formulas for processing fruit in common use in California.

Fruit Treatment in field. In packing houses. . Processing. Packed.

-| Cut in half, sul- | Graded and placed | Dipped in cold or | Moist.
phured 13 hours, in bins not over lukewarm water,
dried in sun on 4 or 5 feet deep; drained, and sul-
trays. sweating takes phured.

place.

Same as peach.....-. Same as peach...... Same as peach ai do, Se Do.
apy at ee eee dO: 52. (o-. S =.|: baMme.as peach. buts: dose oat ee a eee
handled more

carefully.

.| Picked from ground,| Graded and placed | Dipped 1 to 3 min- | Moist;
dipped in lye so- in bins. utesin clear water) Warm.
lution, rinsed in Pa Boapecr dl age te al Ue
clear water, dried drained.
on trays in sun.

aD Soe Picked from ground |..... MO ct 5 or eS Black figs. dipped | Do.
and dried on trays; in boiling brine, |
or dipped in hot drained and
brine, drained, packed. ~-White
dipped in cold figs, dipped in
brine-soda_solu- cold water,
tion, drained, and drained, and
spread on tray S, packed; or dipped
placed in sun un- in boiling brine,
til excess moist- draine d, and
ture is removed, packed. Some
then stacked to - are dipped and
complete drying. sulphured.
FORMULAS.

Brine formula for prunes: Lye, 1 pound to 20 gallons.

Formula for dip for figs before being packed: Salt, 50 ee soda, 3 to 4 pounds;
water, 150 gallons.

Formula for raisins before drying: One quart olive oil and three-fourths pound
powdered caustic soda; water, 1 gallon; cook 30 minutes, add 100 gallons of boiling
water with 44 pounds aie soda; add more caustic soda if desired.

Amount of sulphur to use and time of exposure based on 1,000 pounds of fruit.

THE EFFECT UPON INSECTS OF PROCESSING FRUIT.

It will be observed in Table IT that the processing includes either
dipping in boiling brine or sulphuring.

In the case of figs, when removed from the dipping vat they were
too hot to be handled. When opened the interior was steaming hot,
and it was assumed that no insects could pass through the dip alive.
To prove this point, the following experiments were conducted:

On September 3, 1911, 100 pounds of dried figs, thoroughly infested
by the dried-fruit beetle and Indian-meal moth, were dipped in the
regular dipping solution heated to boiling. Fifty pounds of these
figs were immersed in the dip 45 seconds, and 50 pounds were im-
mersed 90 seconds. The figs were protected from insects when
cooling, and were later put into boxes and sealed. That this dipping
was sufficient to kill all animal life was proved by the total absence

CONTROL OF DRIED-FRUIT INSECTS IN CALIFORNIA. 7

of living insects or of any trace of them when the fruit was examined
four months later, January 14, 1912.

That sulphur fumes are more or less effective in killing insects has
long been known, but in order to prove their efficiency the following
experiments were conducted:

On September 4, 1911, 100 pounds of black figs, which were badly
infested by the dried-fruit beetle, were separated and sulphured in
the regular manner. Upon being removed from the sulphur box
they were immediately placed in cartons and sealed to prevent rein-
festation. They were examined January 14, 1912, and no insects or
evidence of recent work were observed. The sulphuring killed all
insects present in the figs at the time.

An experiment to determine the effect of sulphur fumes upon the
eges of insects was conducted at Sacramento during the summer of
1913. About 25 eggs of the Indian-meal moth, deposited on a dry
fig in a vial, were placed in the top of a sulphur box and given the
usual treatment. None of these eggs hatched, while the eggs kept
as checks hatched in due time.

From the foregoing experiments it is evident that sulphuring the
fruit has a tendency to kill any insects infesting it. In case eggs or
larve are well inside of the fruit, however, it is probable that they
would not be injured; and since the use of sulphur is not sanctioned
by the authorities, and the use of heat, either wet or dry, is so very
effective, the use of a belt heater is recommended.

A BELT HEATER TO DESTROY INSECTS IN DRIED FRUIT.

The belt heater is composed of a chamber in which is run a tier
of belts, each running in the opposite direction to the one above it.
These are so arranged that the fruit can be fed in at the top and will
travel on the top belt until it reaches the roller, when it will fall to
the belt below and be carried in the other direction, and so on down,
the last belt carrying the fruit out of the chamber. A heater, either
electric or steam, is arranged to maintain a temperature of 180° F.,
and by adjusting the speed of the belts the time that the fruit remains
in the heater can be regulated.

An experimental machine consists of six belts, 10 feet long and 5
feet wide, running on 3-inch wooden roUers. The rollers are set on
cold-rolled axles, turned by cast-iron sprockets connected by No. 25
chain, which is so arranged that it reverses the direction of alternate
rollers. To insure even heating an electric fan is so adjusted that
the hot air is blown along the belts, and guides are arranged to direct
the air current onto the belts above. Thus, as the fruit is carried
along by the belts, the hot air is blown over it. Such a machine
arranged to deliver the fruit into a screened packing room (fig. 3)
would insure the fruit against contamination before packing.

8 BULLETIN 235, U. S. DEPARTMENT OF AGRICULTURE.

The fruit should remain in the heater sufficiently long to raise it
to 180° F. This temperature will kill all insect life.

PROTECTING DRIED FRUITS FROM INFESTATION.

Although some damage results from the infestation of dried fruit
stored in bins in the packing house, the greatest loss occurs after the
fruit has been packed. .

The fruit which is separated and dipped into hot solutions (212° F.)
before being packed is by this process sterilized so far as insects are
concerned. It has been found that such fruits as peaches, pears,

and apricots, which are not dipped in such solutions, can be sterilized
by dry heat before they are moistened, preparatory to packing.
The major problem is one of preventing infestation after the fruit
is sterilized and packed. Successful experiments with the use of a
sealed carton (fig. 4) to protect cereals from insect attack?’ led the
writer to work out a similar process for dried fruits.

Figs put up in small packages were found convenient for the fol-
lowing preliminary experiments begun at Fresno, Cal., October 1,
1913. Hot figs were taken from the dipping vat, pressed into bricks,
wrapped in the regular paper, and placed in cartons. Careful watch
~ was kept for infesting insects, and none was seen near the figs during
the packing process.

1Parker, William B. A Sealed Paper Carton to Protect Cereals from Insect Attack. U.S. Dept.
Agr., Bul. 15, 8 p., 8 fig., Oct. 16, 1913.

. Bul. 235, U. S. Dept. of Agriculture. PLATE III.

eee PWM Ni ech ipapsacabaied

Fic. 1.—PATTERN OF THE INNER SEAL. (ORIGINAL.)

en RN a a erE

BUX SEALED.

sng

ecnenersgesnaraenstcteenet

Fic. 2.—METHOD OF USING THE INNER SEAL. (ORIGINAL.)

Fia. 3.—HOw THE PACKAGES STOOD THE SHIPPING TEST. (ORIGINAL.)

THE INNER SEAL: A SANITARY INSECT-PROOF PACKAGE.

Bul. 235, U. S. Dept. of Agriculture. PLATE IV.

Fic. 2.—BRICKS OF FIGS, SHOWING THE RESULT OF SEALED CARTON EXPERIMENTS.

At leit, unsealed brick. Note dried sugaring and infested condition. At right, sealed brick.
Note moist condition. (Original.)

PROTECTING DRIED FRUITS AGAINST INSECTS.

CONTROL OF DRIED-FRUIT INSECTS IN CALIFORNIA. 9

Of these cartons 16 were sealed as shown in Plate III, figure 1,
and 16 left unsealed. Of the unsealed ones, 8 were so prepared that
the wrapping paper was slightly torn. This condition is one fre-
quently found in packages of figs put up by the girls in the packing —
house.

The 32 cartons prepared as described above were brought to
Sacramento and placed in an insect-tight box in which were then
placed large numbers of larve and adults of Plodia interpunctella,
Carpophilus hemipterus, and G'nathocerus (Echocerus) maxillosus Fab.
The box was then sealed so that the insects could not escape, and
they were given every chance to infest the cartons.

At the conclusion of these experiments, April 16, 1914, all but two
of the unsealed
cartons were found
to be infested,
while the sealed
ones showed no
evidence of insects
having entered.
It was observed
that the larve of
Plodia interpunc-

tella had in some
u ik Fig, 4.—Diagram of carton, showing method of applying label to protect
p laces broken inclosed cereal from insect attack. (Author’s illustration.)

through the thin ?
paper used to wrap the bricks of figs before they are placed in the
eartons.t. It had previously been supposed by the packers that this
paper if preserved intact would prevent insects from reaching the
fruit.

The foregoing experiments will serve to prove the efficiency of a
sealed carton in protecting packed dried fruit from insect attack.

SEALED PACKAGES FOR DRIED FRUIT.

Packages of dried fruit weighing less than 5 pounds are so nearly
the size of the cartons used for cereals that, except for the high labor
cost of sealing, the method used with the cereal carton could be
readily applied to dried fruits. With the 10, 25, and 50 pound pack-
ages, however, the cost of such sealing is excessive, and the wooden
boxes used can not be thus sealed to advantage, as the seal is easily
broken by rough handling. To obviate this difficulty a light paper
carton fitting inside the wooden box, and sealed before the top was
nailed on, was constructed, but the cost of these cartons and the
additional labor required to pack them prohibited the employment

1A heavy paraffined paper appears effective in preventing insects from eating through.

10 BULLETIN 235, U. S. DEPARTMENT OF AGRICULTURE.

of this method. A fiber-board carton was then selected which could
be sealed, or in which had been placed an inner seal, to prevent the
entrance of insects. Such a package to be successful should stand
the same shipping conditions as a wooden box and should not, when
sealed, greatly exceed the latter in cost. A carton of the following
specifications was tested to determine its shipping qualities:

Certificate of box maker.—This box is made of three-ply or more, fiber board or pulp
board, outer ply waterproofed.

Bachs pyre oso feet hate eee cae Be Re eee cc ee eee inch.. 0. 016
(hie kness not.less than Combined: board 3.. 0 sosee 6 nee do 080
Resistance (Mullen test), combined board. .....-... pounds per square inch.. 200
Dimension limit, length, width, and depth added.-................... inches. . 65
Gross weiehit lemits) 2 te ee oe ee pounds. - 65

SHIPPING TESTS OF FIBER-BOARD PACKAGES.

Three 25-pound boxes (Pl. III) made according to the foregoing
specifications were filled with 25 pounds of dried peaches, sealed, and
given the following shipping tests:

Box No. 1 was shipped by express from Sacramento, Cal., to Port-
land, Me., and back, or about 6,000 miles, durmg which trip it was
handled by at least 18 men. This box arrived in Sacramento in good
condition and is shown in Plate III, figure 3.

Box No. 2 was shipped from Sacramento, Cal., to Fargo, N. Dak.,
as one of the bottom boxes in a car of 25-pound boxes of dried fruit.
Except for one place where the sharp edge of a wooden box had worked
up the edge, this box arrived at its destination in fine condition, as
illustrated in Plate III, figure 3. This rubbing would not occur in a
carload of fiber-board boxes.

Box No. 3 was sent to San Francisco by Parcels Post, where it was
trucked around the wharves, given a thorough test, and examined
by several packers and by the agent of one steamship company. It
arrived in Sacramento in good condition, after having stood the test
and having been pronounced a good shippmg package for dried
frome: “(el EE tio 3.)

The foregoing tests proved that the 25-pound package of dried fruit
could be shipped long distances, and its shipping qualities compared
very well with the wooden box.

These fiber-board boxes (Pl. IIT) weigh much less than the wooden
box, and the saving on the freight would be considerable. In the
case of the 25-pound box the saving per car on the basis of $1.10
per 100 (freight rate) is about $23. It was estimated that the adop-
tion of this style of package would save one company approximately
$40,000 annually.

CONTROL OF DRIED-FRUIT INSECTS IN CALIFORNIA. 11
THE SEAL.

The fiber-board package was found to be tight, except at the cor-
ners and where the flaps meet in the middle of the sides. An attempt
was made to seal these places with gummed tape, but the labor
required to do this increased the cost of packing to such an extent
as to make the method unfeasible.

An inner seal was then so constructed that when the carton was
regularly sealed there would be no cracks or openings at the corners.
(See Pl. ITT, fig. 1.)

The inner seal appears practical from the packer’s point of view,
but the carton manufacturer claims that it would be difficult to
make it cheaply enough without special machinery, although this
would probably be made were there a demand for such cartons.

ADVANTAGES OF THE SEALED CARTON FOR DRIED FRUIT.

As long as dried fruit can be processed so that mold is no more
prevalent in sealed packages than in unsealed ones the disadvantages
of this type of package, with the possible exception of the extra cost,
aré negligible. The advantages, on the other hand, are several.

The main object of the sealed carton is the exclusion of infesting
insects. This is accomplished very successfully and so solves a large
portion of the present problem.

It also prevents the evaporation of moisture from the fruit, and
thus for a long time preserves the fruit in the same moist condition
in which it was packed. Plate IV, figure 2, shows two bricks of figs
packed October 1, 1913, and opened April 16, 1914. The brick on
the left was put up in an ordinary carton, and, as will be observed,
it was dried, sugared, and became infested, while the one on the right,
which was put into an ordinary carton, but sealed, is in practically
the same condition as when packed. These two bricks were kept
under the same conditions; in fact, were in the same box. From the
foregoing data it is evident that fruit properly packed in sealed cartons
will be protected from infestation and will remain in a moist condition
much longer than when packed in an ordinary carton or box.

OTHER SEALED PACKAGES.

In an attempt to find a small and attractive package for their fruit
one packing company in California evolved a round carton with a
cover that fitted over the end like the cover of a baking powder can,
as shown in Plate IV, figure 1. A printed label pasted around the
edge of the carton formed in experiment a very effective seal. This
carton appears to be satisfactory for small packages, but the shape is
such that more room is required for shipment than is the case with
the square package, and it is not as practical for the larger sizes.

12 = BULLETIN 235, U. S. DEPARTMENT OF AGRICULTURE.

When objections to the inner seal were presented the writer imme-
diately investigated other possible methods. Among several which
were suggested, the use of a waxed sealing paper wrapped around
bricks of fruit and sealed with a hot iron seemed very promising.!
It was found that bricks of apricots, prunes, and pears up to 10 pounds
in weight could be successfully made and wrapped in the waxed paper,
and that by placing a piece of sheet iron on top of the brick of fruit
before folding the paper over, a smooth surface could be obtained for
the application of the sealing iron. After the top is sealed the sheet
iron should be quickly removed. The hot iron may then be applied
to the ends of the paper, making them tight, and afterwards the ends
may be folded up and the brick placed in a large carton. Plate V,
figures 1 and 2, shows the effect obtained by using such a paper seal,
which, when properly sealed, renders the package insect proof. The
cost of packing dried fruit in such a package has not been determined,
but the writer believes that it will be found economical in many
packing houses.

This method combines the advantages of an insect-proof package,
a 5 or 10 pound unit, and a 25 or 50 Foca fiber-board carton, which
is lighter and pr Ghabey cheaper than the wooden box.

While in the field the writer observed a package formed of an
ordinary raisin carton which was sealed in a waxed sealing paper.
The sealing was done by machinery which, except for the initial
expense of the machine, would make the process very rapid and
economical. Such a package might prove very efficient for dried
fruits put up in from 1 to 5 or even 10 pound packages.

Several packers have reported the presence of mold in the ordinary
wooden boxes of dried figs. Plate VI, figure 1, shows such a condi-
tion. This was observed to occur more frequently in the sealed round
boxes previously mentioned, and it appears that if the sealed carton
is to be used for dried fruit the problem is a very important one.

From examinations of moldy fruit and from investigations of the
condition of the fruit when packed, the writer concludes that condi-
tions favorable to the growth of mold occur only when the fruit is
too wet when packed, either through excessive processing or improper
drainage. One packer stated that when the fruit was taken directly
from the hot dip and packed in sealed boxes a large percentage of the
cartons became moldy. On the other hand, if the fruit was allowed
to drain thoroughly and stand in lug boxes or in a heap for. several
hours before being packed, the moisture became equalized and mold
rarely developed. (Pl. VI, fig. 2.) To establish these statements
and observations finally the following experiments were conducted:

On July 28, 1914, four lots of figs were processed by dipping in
boiling water for one minute. Lot ‘No. 1 was dried in n the sun until

1 Se eied by Mr. J. H. Green, of San Francisco.

Bul. 235, U.S. Dept. of Agriculture. PLATE V.

Fic. 1.—A CARTON WRAPPED AND SEALED BY THE MACHINE. (ORIGINAL.)

Fig. 2,—CLEAN AND WHOLESOME; MOISTURE AND INSECT PROOF. PARAFFIN-WAXED
PAPER SEAL APPLIED TO A CARTON OF RAISINS. (ORIGINAL.)

INSECT-PROOF PRODUCTS OF THE WRAPPING AND SEALING MACHINE.

es

Bul. 235, U. S. Dept. of Ag

Fig. 1.—MOLDY CONDITION OF FIGS IN ROUND SEALED CARTON. FIGS PACKED TOO
WET. (ORIGINAL.)

Fia, 2.—PERFECT CONDITION OF FIGS PACKED IN ROUND SEALED CARTONS. EXCESS
MoISTURE REMOVED BEFORE PACKING. (ORIGINAL.)

PRESENCE OR ABSENCE OF MOLD IN SEALED CARTONS OF DRIED FIGS.

Bul. 235, U. S. Dept. of Agriculture. PLATE VII.

A VALUABLE ADJUNCT TO INSECT-PROOF PACKING.

A carton wrapping and sealing machine, with a capacity of 10,000 per day of 8 hours, at a total
cost of less than $1 per thousand. (Original.)

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CONTROL OF DRIED-FRUIT INSECTS IN CALIFORNIA. 13

all the surface moisture was gone. Lot No. 2 was dried in the sun a
few minutes. Lot No. 3 was allowed to drain and cool thoroughly
in the shade. Lot No. 4 was allowed to drain a few minutes and
was packed while still hot and damp. All were packed in Mason
jars, infected with spores from growing fungus, and sealed up.

On examination one month later no fungous growth was found to
have developed on Nos. 1, 2, and 3, but No. 4, the lot which was
packed wet and hot, had a very good growth of the fungus.

The experiment was repeated on September 1, dipping the figs in
the hot water three minutes instead of one. On examination two
weeks later it was found that in lot No. 1 no growth of fungus had
developed. In lots 2 and 3 slight growths were present, and in lot 4
a heavy growth. The same figs were used in both experiments, and
by the time they had been put through the boiling water the second
time their surfaces were softer and stickier than they should be, and
hence were good media for fungous growth.

These experiments confirm the earlier observations, namely, that figs
thoroughly drained or dried and cooled before packing are less likely
to develop fungous growth than those packed while still damp and
ee A CARTON WRAPPING AND SEALING MACHINE.

Several machines are now being manufactured which do away with
the slow and expensive method of wrapping and sealing cartons by
hand. Such a machine is shown in Plate VII. The cartons are fed
into the hopper at the top and the waxed paper is fed automatically
or by hand. ‘The machine wraps the waxed paper neatly and tightly
around the carton and seals it air-tight by means of electrically heated
plates. One operator is required when equipped with the automatic
paper feed, and two without. This particular machine was made
to wrap cartons 8 by 3 by 3 inches. It will wrap and seal a mini-
mum of 25 to 30 per minute, or about 10,000 per day of eight hours,
The cost based on this output, including the waxed paper, wrapping,
sealing, power to operate, and wages of the operator, will be less
than $1 per 1,000: The maximum output will be from 15,000 to
20,000 cartons per day, with a cost at this rate of from $0.80 to $0.90
per 1,000. |

At present, by the hand-wrapping method, one girl will average
1,000 cartons per day. Thus the machine will easily do the work of
a dozen or more girls.

The cost of hand-wrapping the package referred to is given as $1.75
per 1,000. Using the minimum output of the machine for compari-
son, the saving in one day’s run would be over $7, at which rate the
machine would pay for itself in less than four months, since it may
be purchased capable of handling any size of carton desired by the
purchaser at a retail price of about $600.

14 BULLETIN 235, U. S. DEPARTMENT OF AGRICULTURE.

A machine of this nature would be available and practical not
only for wrapping and sealing cracker and cereal cartons, but also
for raisins, currants, figs, prunes, and all small packages of other
dried fruits.

PREPARATION OF A STERILE PACKAGE OF DRIED FRUIT.

A description has been furnished of a method of preparing packages
of cereals so that they will not become infested. This process is
being successfully carried out by several large mills, the only real
difficulty arismg from the cost of sealing the carton. This objection
is being gradually overcome.

The process consists in running the cereal through a sterilizer and
then through a clean chute directly into an insect-free packing room,
where it is packed in sterilized cartons and sealed. The writer be-
heves that such a process can be applied to dried fruit, and the follow-
ing suggestions are made to that effect:

In order to sterilize the fruit so far as insects are concerned it is
necessary to heat it to 180° F. With the fruits which are regularly
dipped in hot solutions this heating is readily accomplished, but in
the case of those which are dipped in cold solutions before being
packed the use of the belt heater described on pages 7-8 is suggested.

After sterilization by one of the foregoing processes the fruit must
be protected from reinfestation, and the use of the screened packing
room, a plan for which is shown on page 8, figure 3, and described
below, will serve this purpose nicely.

The fruit should be run directly from the sterilizer or dipping vat
into the packing room, where it is packed and sealed. It may then
be removed to a warehouse, and if properly sealed it will not become
infested by insects.

THE SCREENED PACKING ROOM.

A simple packing room (fig. 3) can be cheaply constructed by
covering a light framework with lath, cloth, and paper. The windows,
the floor, and ali corners and joints should be made tight, and venti-
lation accomplished by blowing air through an opening covered with
cheesecloth or No. 20 screen wire. Such a packing room can be
constructed to admit plenty of light and air and still be free from
insects. Whenever necessary the openings may be closed and the
room thoroughly fumigated.

Note.—The writer has observed as many as 10 eggs of insects on the inside of a carton in a cereal mill.
It is advisable, therefore, to sterilize all cartons before filling them. This may be readily done by placing
a truck load in a heating chamber over night or during the day.

CONTROL OF DRIED-FRUIT INSECTS IN CALIFORNIA. 15

SUMMARY AND CONCLUSIONS.

The foregoing observations and experiments have brought out the
following points:

A considerable financial loss due to the infestation of dried fruit by
insects is experienced by packers, wholesale men, and retail dealers.

There are several species of insects which attack dried fruits on
the Pacific coast, but of these the most common and destructive are
the Indian-meal moth and the dried-fruit beetle.

Infestation takes place in the packing house, in the warehouse, and
in the grocery store. The insects find their way to the fruit through
small cracks in the boxes and between the folds of the paper.

All insect life is destroyed in fruits that are put through the boiling
dip, and the processing of other fruits can be accomplished by the
addition of the belt heater to sterilize all fruit so treated.

The use of an insect-free packing room and sterilized cartons or con-
tainers which are sealed before being placed in the warehouses or cars
will protect the fruit from infestation unless the package is broken.

There are several cartons and methods of sealing that can be ap-
plied to dried fruit, but their cost will determine their practicability.

The secret of preparing an insect-free package of dried fruit is to
sterilize it at a temperature of 180° I. and protect it from future
infestation by the use of the insect-free packing room and sealing in
sterile cartons or packages.

The sealed carton not only protects the fruit from infestation, but
it prevents 1t from drying out and preserves it for long periods in the
moist and attractive condition in which it was packed.

Moist fruit can be successfully packed in sealed cartons, provided
attention is paid to the moisture content. The fruit must be care-
fully drained and must not be packed too hot.

Machines have been invented which will successfully wrap and seal
small packages of dried fruit at a moderate cost per thousand.

It is probable that the time is coming when it will be as necessary
to put up dried fruit in sealed packages as it is to pack cereals in
that form to-day.

ADDITIONAL COPIES

OF THIS PUBLICATION MAY BE PROCURED FROM
THE SUPERINTENDENT OF DOCUMENTS
GOVERNMENT PRINTING OFFICE
WASHINGTON, D. C.

AT

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V

WASHINGTON : GOVERNMENT PRINTING OFFICH ; 1915

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