November i5 10251
United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
COLD STORAGE TO CONTROL THE CIGARETTE
BEETLE IN CIGAR TOBACCOS
Joseph N. Tenhet and Clarence 0. Bare l2/-
Division of Stored Product Insect Investigations
The control of the cigarette beetle (Lasioderma serricorne (F.)) in
cigar tobacco by fumigation has never been entirely satisfactory. The
fumigated tobacco must be held in storage until all trace of the fumigant
is gone. With the widespread use of storage at subzero temperatures
for the preservation of other products, cigar manufacturers have become
interested in the possible use of such storage for the control of the
cigarette beetle. Swingle (1) showed that, although all stages of this
insect could be killed in 60 hours with a temperature of 15 F., 3 1/2 to
5 1/2 days were required for the centers of bales of tobacco stored at 100
to cool to 150. Cigar manufacturers have stated that a 3-day exposure
in storage at subzero temperatures would be practical, if effective.
Therefore, experiments were undertaken at Lancaster, Pa., in 1950 to
answer three questions:
Will exposure to very low temperatures injure cigar tobaccos?
At very low temperatures how rapidly will the temperature fall at
different depths in the tobacco.
At different depths in the tobacco how quickly will all stages of the
cigarette beetle be killed?
All the tobacco used in these experiments had been thoroughly sweated
and was in good condition. It was in cases approximately 30 inches wid:,
30 inches deep, and 42 to 48 inches long, and weighing approximately
Test lots of 25 cigarette beetles--4 lots of each stage (adults, z?..
larvae, and pupae) per case--were placed in the center of ea.:h case or
at various depths in the tobacco. Each lot was confined in a perforaced
i', i e work upon which this paper is based was conducted while the
authors were in the Division of 'I ruck Crop and 'arden l:.sect Investigations.
2/ The authors express their appreciation to the General Cigar
Company and the Goodling Electric Company for their assistance in these
In the first experiment five cases of tobacco were placed in cold
storage at approximately -10 F. In three of the cases the tobacco was
in medium order, in one case it was dry, and in one case was soft. The
term "order" refers to a condition of the tobacco leaf in which it contains
sufficient moisture to be pliable and handled readily without breaking. In
these experiments the tobacco in medium order contained approximately
15 to 16 percent of moisture, dry tobacco contained less moisture (usually
about 14 percent), and soft tobacco more moisture (usually about 17
The capacity of the cold-storage chamber was approximately 3,000
cubic feet, and the cold air was circulated in the chamber. Test lots of
cigarette beetles were placed in the center of each case.
At the beginning of the experiment the temperature of the tobacco was
72 F. Later the temperatures in the cold-storage room and of the
tobacco at the center of a case were as follows:
Cold-storage room Tobacco
After 45 hours -10 F. 26 F.
After 69 hours 8 8
After 93 hours 8 4
Unfortunately, thermocouples were not available for this experiment.
The temperature readings, obtained by means of a long metal-jacketed
thermometer thrust into the tobacco, were thought to be unreliable,
because in ar air temperature of -10 F. it is possible that the cold
would be carried into the bulb of the thermometer by the metal jacket.
Alter 4 days the cases of tobacco were removed from cold storage
aind the insects were removed and examined. Mortalities of adults and
larvae were recorded after 3 to 4 hours and incubation of eggs and
emergence of adults after 3 to 6 days. Table 1 shows that enly a few of
the test insects sui vived, except in the soft tobacco.
Table 1. --Percent survival of cigarette beetles in the center of cases of
cigar tobacco exposed for 4 days to approximately -10 F.
Type of Moisture con-
e f M c Adult Larvae Pupae Eggs
tobacco edition of tobacco
Wisconsin binder Dry 0 0 0 0
Medium order 0 2 0 0
Pennsylvania filler Soft 41 93 40 7
Connecticut binder Medium order 8 18 1 0
Havana seed binder -do.- 0 0 0 0
(check) -do.- 98 100 100 96
Leaf-tobacco experts carefully examined all the tobacco several days
after it had been removed from cold storage. They concluded that none
of it had been adversely affected by exposure to cold. All the tobacco was
dry and hard when first removed from the cold room, but as it warmed
up it absorbed moisture from the air. After 2 to 4 days the tobacco had
returned to normal summer temperature, and was at least in as good
condition as before it was exposed. Some of the dry tobacco was slightly
improved, as it had picked up a little more moisture.
In the second experiment 10 cases of tobacco were placed in cold
storage at approximately -100 F., as described in the first experiment.
Four of the cases were of Pennsylvania filler, four of Wisconsin binder,
and two of Connecticut binder. All the tobacco was in medium order
except one case of Pennsylvania filler, which was soft. Five cases,
including the one of soft tobacco, were held in cold storage for 3 days,
one case was held for 4 days, one for 5, and three for 6 days. In two
cases thermocouples were placed at 5, 10, 15, and 21 inches from the
approximate center of one end. The thermocouple 21 inches from the
end was at approximately the center of the mass of tobacco. One of
these cases was the soft tobacco held in cold storage for 3 days, and the
other case was in medium order and held for 6 days.
Test lots of the various stages of the cigarette beetle were placed in
each case--4, 8, 12, and 16 inches deep into the tobacco from the approxi-
mate center of one end. Check lots were placed at the same locations in
four cases of the same types of tobacco, and held at summer storage
temperature--about 80-85o F. The temperature of all the tobacco at
the beginning of the experiment was 84-86 F.
The decreases in temperature of the tobacco at different depths in
the case are shown in figure 1. At a depth of 5 inches only 1 day was
required for the tobacco temperature to fall to 0 F., as compared with
more than 3 days at 10 inches and more than 5 days at 15 inches. At
21 inches, in the center of the case, the temperature dropped a little
more slowly than at 15 inches during the first 4 days, but by the sixth
day the temperatures at these two locations were the same.
Table 2 shows that a 3-day exposure killed all insects at the 4-inch
depth, and also at the 8-inch depth in the tobacco of medium order. As
in the first experiment, an appreciable percentage of larvae and adults
survived at this 8-inch depth in the soft tobacco. After 4 days' exposure
mortality was complete at both the 12- and 16-inch depths in all tobacco.
Table 2. --Percent survival of cigarette beetles at different depths in
cases of cigar tobacco held for 3 days in cold storage at approximately
Moisture condition Depth of insects Adults Larvae Pupae Es
of tobacco in tobacco
Medium order 4 0 0 0 0
8 0 0 0 0
12 0 8 0 0
16 0 7 0 0
Soft 4 0 0 0 0
8 56 48 4 0
12 100 60 36 2
16 48 80 44 5
Medium order (check) 4 100 98 100 100
8 100 100 99 98
12 100 98 95 100
16 100 98 96 98
In the third experiment four cases of tobacco were placed in a com-
mercial cold-storage plant at -20 F. for 3 days. The air in this plant
was not circulated as in the other tests. One case was dry, two cases
were in medium order, and one was soft. In three cases, thermocouples
were placed 4, 8, 12, and 16 inches from the approximate center of one
end. Test lots of all stages of the cigarette beetle were placed in each
case, as in the preceding experiment. Check insects were held at room
The temperature decrease was slightly greater in the dry tobacco
than in the tobacco of medium order, and slightly less in the soft
tobacco (fig. 2).
The effect of the moisture content of the tobacco on the mortality of
test insects is shown in table 3. All the insects were killed at the 4-inch
depth. At the 8-inch depth there was no survival in dry tobacco, negli-
gible survival in tobacco in medium order, and appreciable survival,
especially of larvae, in soft tobacco. At the 12- and 16-inch depths
survival increased with the moisture content of the tobacco.
Table 3. --Percent survival of cigarette beetles at various depths in
cases of cigar tobaccos of different moisture content, held for 3 days
in commercial cold storage at -200 F.
Depth of insects
Medium order (check)
Three experiments on the control of the cigarette beetle (Lasioderma
serricorne (F.)) in tobacco exposed to subzero temperatures were con-
ducted at Lancaster, Pa., in 1950. In the first experiment all stages of
the beetle were placed at the center of tobacco held in cold storage
chambers at approximately -10 F., and in the second experiment they
were placed at various depths in the tobacco. In both these experiments
the air was circulated. In the third experiment, the insects were placed
in tobacco in a commercial cold-storage plant at -20 F. iin which the
air was not circulated.
The low temperatures did not injure any of the tobacco.
In cases stored at -10 F. only 1 day was required for the tobacco
temperature at a dep-'. of 5 inches to fall to 0 F., or compared with
more than 3 days at 10 inches and more than 5 days at 15 inches.
The mortality of thie insects depended upon the circulation of air in
the storage and upon the moisture condition of the t bacco( Exposure
to -10 F. in circulated air was more effective than exposure to -20
in still air. For tobacco of medium order a 3-day exposure to -10
with the air circulated was as effective as fumigation in an atmospheric
chamber. For soft tobacco an exposure of 4 to 5 days was necessary.
(') Swingle, M. C.
1938. Low temperature as a possible means of controlling the
cigarette beetle in stored tobacco. U.S. Dept. Agr.
Cir. 462, 8 pp.
Figure 1. --Decreases in temperature at four depths in
cases of cigar tobacco held in cold storage for 6 days
at approximately 10 F.
UNIVERSITY OF FLO RIDA
II I I I 0 I I 3 II 61 1I
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Figure 2. --Decrease in temperature at a depth of 16 inches
in cases of cigar tobacco of different moisture content
held in cold storage for 5 days at approximately -10 F.