Residual sprays for use against the confused flour beetle

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Material Information

Title:
Residual sprays for use against the confused flour beetle
Physical Description:
15 p. : ; 27 cm.
Language:
English
Creator:
Cotton, R. T
Frankenfeld, J. C ( Justus Carl ), b. 1901
Dennis, N. M ( Norman McLeod ), 1922-
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
United States Department of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:

Subjects

Subjects / Keywords:
Confused flour beetle -- Control   ( lcsh )
Spraying and dusting in agriculture   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Statement of Responsibility:
R.T. Cotton, J.C. Frankenfeld, and Norman M. Dennis.
General Note:
Caption title.
General Note:
"E-766."
General Note:
"December 1948."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030293292
oclc - 780096324
System ID:
AA00025157:00001

Full Text


December 1948


United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine



RESIDUAL SPRAYS FOR USE AGAINST
THE CONFUSED FLOUR BEETLE

R. T. Cotton, J. C. Frankenfeld,
and Norman M. Dennis, Division of
Cereal and Forage Insect Investigations


Insects harbored in the woodwork of flour mills, warehouses, rail-
way boxcars, and granaries are not readily controlled by fumigation.
Until recently the only sprays available for use in such places have
been of the contact type, which kill only those insects that are actually
hit with the spray. These sprays consist chiefly of an odorless, stain-
less, kerosene-type oil fortified with small -mrounts of pyrethrum,
thiocyanates, rotenone-.containing material, or various combinations
of these toxicants. Although effective against moths and other soft-
bodied flying insects, they are not highly toxic to many of the insect
pests of stored grains and milled-cereal products.
During the past few years a number of new and highly effective in-
secticides have become available commercially-DDT, TDE, methoxy-
chlor, gamma benzene hexachloride, chlordane, chlorinated camphene,
parathion, and piperonyl butoxide-pyrethrum formulations. Sprays
containing them are not only effective by direct contact, but the in-
secticidal residues they leave on sprayed surfaces are of great value
in reducing insect populations that have become established in the wood-
work of walls, floors, partitions, bins, and machinery. Some of these
residues may remain effective for a year or mor- ', and sprays contain-
ing them are known as residual sprays.
The toxicity of these insecticides to the confused flour beetle
(Tribolium confusum Duv.) has been determined in the laboratory under
various conditions. This insect was chosen for test purposes, because
it is the most important insect pest of fl'. u. mills, is more resistant
to insecticides than are most insects, a is u e to crawl up the
smooth sides of glass vials or plastic iZl s us'- U to confine it on sprayed
areas.
This report is not intended as a r,- o imendation of any particular
material or formulation for commercial use.


E-766






-2-


Technique

The insecticides under discussion may be formulated in five ways-
as dusts, wettable powders, emulsions, solutions in oil or other solvent,
and aerosols. Although all these formulations may prove useful for the
control of insect pests of stored grains and milled cereals, dusts and
aerosols are not discussed in this paper. In the experiments reported
herein the various toxicants were applied as sprays, in carbon tetra-
chloride or acetone-kerosene solutions, in xylene emulsions, and as
wettable powders dispersed in water, at the rates of 50 and 10 mg. in
2 ml. of spray per 1/4 square foot. These dosages are approximately
equivalent to 5- and 1-percent sprays applied at the rate of 1 gallon
per 1,000 square feet. Parathion was tested only as a wettable powder
containing 15 percent of this chemical.
Kerosene-oil solutions were prepared by dissolving 5 grams of the
solid insecticide in 10 ml. of acetone and adding 90 ml. of oil. These
stock solutions and chlordane, which was already in solution, were
further diluted with oil to give the desired concentration.
Stock emulsions were prepared to contain 5 grams of insecticide,
10 grams of xylene, and 5 grams of emulsifier in 80 ml. of water. The
stock emulsions were diluted with water to give the desired concentra-
tion.
Known quantities of each toxicant in dilute sprays were applied to
various types of surfaces. When the spray deposits were dry, adults
or immature stages, in triplicate lots of 10, were confined on each of
the sprayed surfaces under glass vials 1 inch in diameter and 4 inches
high. At the end of the exposure period the insects were removed to
clean glass vials containing fresh flour and held for observation.
Mortality counts were made every 2 days. Maximum mortality of
adult beetles was usually obtained in 12 days. Larvae were consider-
ably more resistant, and it was necessary to hold some of them 30 days.

Comparative Effectiveness and Speed of Action

The comparative effectiveness and speed of action of the various
insecticide residues were determined in tests conducted with glass
plates to avoid differences due to absorption. The results of tests
with 50-mg. dosages are given in table 1.
A dosage of 50 mg. per 1/4 square foot of gamma benzene hexa-
chloride I/ in a carbon tetrachloride solution was the most rapid in its
toxic action. A 30-minute exposure to the residue of this material
killed all flour beetle adults within 4 days, and longer exposures did

I/ Tests with this material were restricted to the isolated gamma
isomer.






-3-


not hasten the death of the insects. DDT and chlordane were as toxic
as gamma benzene hexachloride, but slower in action at all exposures
under 24 hours. TDE was slightly less toxic at a 30-minute exposure,
but at all other exposures killed as rapidly as did DDT or chlordane.
Methoxychlor and chlorinated camphene were much slower in action,
except at the 24-hour exposure to chlorinated camphene and at the 6-
and 24-hour exposures to methoxychlor.
As the dosages were decreased there was a decrease in the effec-
tiveness and also the speed of action of the spray deposits that was
most noticeable with chlorinated camphene, methoxychlor, and gamma
benzene hexachloride. At the 10-mg. dosage DDT was the most effec-
tive and most rapid in action, although with exposures longer than 30
minutes chlordane equaled it in both effectiveness and speed of action.
At this dosage level gamma benzene hexachloride, TDE, and methoxy-
chlor were comparable in effectiveness and speed of action for nearly
all exposure periods. They were slower in action than DDT and chlor-
dane at exposures shorter than 6 hours. Chlorinated camphene was less
effective and slower in action than the other insecticides at all expo-
sures, except the 24-hour period. At a 24-hour exposure, all compounds
appeared to be equally effective at all dosages tested.
When the six compounds were applied in solution in refined kero-
sene, in em.ilsions, and as wettable powders, the type of formulation
used had a marked effect upon the effectiveness and the rate of kill of
the spray deposit.
At the 50-mg. dosage emulsions were consistently more efficient
and more rapid in action than wettable-powder suspensions, or carbon
tetrachloride or acetone-kerosene solutions. Furthermore, the per-
formance of the six compounds was more nearly uniform in emulsions
than in the other formulations. Gamma benzene hexachloride appeared
to be slightly the best, but there were no really significant differences
between its performance and that of DDT and chlordane. All three com-
pounds were distinctly but only slightly more effective than TDE,
methoxychlor, and chlorinated camphene.
Dispersions of wettable powder in water were in general distinctly
less effective and much slower in rate of kill than emulsions of carbon
tetrachloride solutions. However, wettable-powder suspensions of DDT
and gamma benzene hexachloride were only slightly slower in action
than the corresponding carbon tetrachloride formulations for exposures
of 30 minutes and 1 hour. The two compounds were more effective and
faster in action for all exposures than the corresponding acetone-kero-
sene solutions, which were in general less effective and slower in rate
of kill than other formulations. However, chlordane, TDE, methoxy-
chlor, and chlorinated camphene were slightly superior in acetone-
kerosene solutions than as wettable powders.
At lower dosages greater differences were noticeable in the effec-
tiveness of the several formulations of the various compounds. With a






-4-


dosage of 10 mg. per 1/4 square foot DDT as a wettable powder was
significantly more effective and quicker in action than all other com-
pounds, except parathion, at all exposures under 6 hours. In the emul-
sion DDT was almost equaled by chlordane; chlorinated camphene ranked
third in effectiveness. In general the emulsions were superior in action
at this dosage level.
Parathion was far the most effective and most rapid in action of all
the compounds tested. In tests, the results of which are not included in
the data of table 1, an exposure of 30 seconds on plates sprayed with a
10-mg. dosage killed all flour beetles within 2 days after exposure. In
the 24-hour exposure, all beetles were dead when removed from the
plates.

Duration of Effectiveness of Spray Deposits

Great differences were found in the duration of effectiveness of
deposits of the insecticides. The effectiveness also varied with the
type of formulation and the character of the surface to which it was
applied. Solutions in carbon tetrachloride or acetone-kerosene, xylene
emulsions, and wettable powders were applied as sprays to glass, wood,
cardboard, and cement surfaces. When the sprayed surfaces were dry,
triplicate lots of adult flour beetles were exposed to them for 6 or 24
hours in the manner previously described, and the mortalities recorded
every 2 days for 12 days after exposure. The sprayed surfaces were then
set aside where they were exposed to ordinary indoor temperatures and
daylight but not to direct sunlight. Similar exposures were made at the
end of each week or month thereafter until deposits failed to show any
appreciable insecticidal effect.
At the 50-mg. dosage DDT residues from all formulations remained
100 percent effective on glass and wood surfaces for 1 year. Carbon
tetrachloride solutions and wettable-powder suspensions remained 100
percent effective on cardboard surfaces for 1 year also, but xylene
emulsions of DDT were only partially effective after 6 months. On un-
finished cement surfaces the only DDT formulation remaining 100 per-
cent effective after the initial exposure was the wettable powder. This
formulation of DDT remained 100 percent effective for 2 months.
At the same dosage rate, chlorinated camphene residues on glass
from carbon tetrachloride solutions, acetone-kerosene solutions, and
wettable-powder suspensions remained 100 percent effective for 1 year
and xylene emulsions for 8 months. On wood surfaces carbon tetra-
chloride solutions and wettable-powder suspensions were equally effec-
tive for 1 year, but no formulation of chlorinated camphene was effective
after the initial exposure. On cardboard surfaces carbon tetrachloride
solutions remained 100 percent effective for 8 months and wettable-
powder suspensions for 11 months. Xylene emulsions were ineffective
after the initial exposure. On unfinished cement the residues from






-5-


chlorinated camphene sprays were ineffective after the initial
exposure.
Chlordane, gamma benzene hexachloride, TDE, and methoxychlor
were effective only for much shorter periods, even on nonabsorbent
surfaces (table 2). Chlordane and gamma benzene hexachloride de-
posits are volatile. Of two types of chlordane tested, one remained
effective much longer than the other, probably owing to its lower rate
of volatilization.
In general the effectiveness of residual sprays decreased with the
increase in the absorptive property of the surface sprayed. However,
the type of formulation also had a distinct relationship to the effec-
tiveness of spray deposits on absorptive surfaces. The short duration
of effectiveness of all spray deposits on unfinished cement surfaces
may have been due to the highly absorptive nature of the cement,
combined with the action of the free lime on the spray materials.
More of the DDT was left on the surface of the cement, where it was
available to kill insects coming in contact with the sprayed surface,
by the water suspension than by the water solution or emulsion.
On absorptive surfaces acetone-kerosene solutions and emulsions
of the compounds of low volatility were much less efficient than the
corresponding water suspensions of wettable powders. For immediate
results the more volatile compounds, such as chlordane and gamma
benzene hexachloride, were the most effective, since the fumigation
effect of these spray deposits was about the same as the contact effect
and persisted for about the same l'.Kigth of time.
When wood surfaces are paintedC, the type of finish is likely to in-
fluence the performance of the spray deposit. In studying the duration
of effectiveness of DDT spray deposits recently painted wood surfaces
were sprayed with xylene emulsion and wettable-powder formulations
of DDT. On wood surfaces finished with cold-water paint or flat-oil
paint, but not with enamel, the effectiveness of both emulsion and wet-
table formulations of DDT was much less than on unpainted wooden
surfaces. On an enamel finish the emulsion formulation was only
slightly less effective than the wettable-powder formulation. In all
tests the wettable-powder formulations were superior to the emulsion
formulations.

Use of Sealers on Cement Surfaces

In an endeavor to improve the performance of residual spray de-
posits on unfinished cement surfaces, several types of sealing mate-
rials or plasticizers were used as preparatory treatments and in com-
binations with DDT and chlordane sprays. Pretreatment with magnesium-
zinc-silicofluoride greatly improved the performance of both sprays.
Following this pretreatment excellent kills of the flour beetle were
obtained, when the beetles were exposed to cement surfaces 3 months






-6-


after they were treated with either DDT or chlordane sprays. The
addition of ammonium stearate to a DDT emulsion caused a temporary
increase in toxicity, but aluminum stearate added to oil solutions of
DDT did not increase its efficiency on cement surfaces. No improve-
ment in the performance of chlordane sprays was obtained by the addi-
tion of stearates.

Effect of Mixing Residual Spray Materials

Mixtures of DDT with chlordane and with gamma benzene hexa-
chloride in various proportions were applied to wooden plates and
tested against the confused flour beetle. The results failed to show
any advantage as a result of combining the materials.

Effect of Temperature and Light on Spray Deposits

When residual spray deposits were being tested, it was noticed that
the duration of their effectiveness was influenced by temperature. There-
fore a series of experiments were set up, in which glass plates were
sprayed with various materials dissolved in carbon tetrachloride. The
plates were then stored in darkness at constant temperatures of 800
and 42 F. At six monthly intervals these glass plates were removed
to the testing room, where adults of the confused flour beetle were con-
fined on them for 1, 3, 6, and 24 hours. Storage in darkness at the
higher temperature extended the period of 100-percent effectiveness
of chlordane, gamma benzene hexachloride, and TDE by 3 months, and
that of methoxychlor by 5 months; at the lower temperature chlordane
and gamma benzene hexachloride were still 100 percent effective after
5 months.

Minimum Effective Dosages of DDT

The excellent results obtained with the 10-mg. dosage of DDT led to
an investigation of lower dosages of DDT in solution in acetone-kerosene
and in carbon tetrachloride, and in water suspensions of a 50-percent
wettable powder. Glass plates were sprayed with these formulations in
dosages of 5, 2.5, and 1 mg. of DDT per 1/4 square foot. The effective-
ness of the spray residues against flour beetles was determined over a
period of 8 months after application. The 5-mg. dosage was 100 per-
cent effective in all formulations for both 6- and 24-hour exposures,
but smaller dosages did not hold up satisfactorily. A dosage of 5 mg.
per 1/4 square foot is approximately equivalent to a spray containing
0.5 percent of DDT applied at the rate of 1 gallon per 1,000 square feet.







-7-


Effect of Residual Sprays on Immature Stages
of the Confused Flour Beetle

Eggs and pupae of the confused flour beetle do not appear to be
materially affected by exposure on surfaces that have been sprayed
with residual sprays. Immature stages were exposed for 24 hours to
deposits of DDT, chlordane, and gamma benzene hexachloride that had
been applied to glass plates at the rate of 50 mg. per 1/4 square foot.
Eggs hatched almost normally, the average percentage being 77 after
exposure to DDT, 75 for chlordane, and 47 for gamma benzene hexa-
chloride, as compared with 77 percent for the check. The fumigation
effect of the gamma benzene hexachloride may have caused a slight
reduction in viability of the eggs; however, no fumigation effect was
noticeable with chlordane. Pupae similarly exposed on glass plates
treated with DDT transformed normally.
Larvae of the confused flour beetle are affected by exposure to the
spray residues, although they are much more resistant than the adults.
Data regarding the effectiveness of spray residues from carbon tetra-
chloride solutions of DDT, chlordane, and chlorinated camphene on glass
plates for 6- and 24-hour exposures are given in table 3. By comparison
with table 1 it may be seen that heavier dosages were required to kill
the larvae than the adults, and that a longer period was required for the
residues to become effective.

Effect of a Flour-Dust Coating on the
Efficiency of Spray Residues

The efficiency of a residual spray deposit is reduced when it be-
comes coated with dust. Flour beetle adults were held for 1 week on
wood surfaces that had been treated with DDT at the rate of 50 mg. per
1/4 square foot and covered with a 1/4-inch layer of flour. At the end of
that time 40 percent of the insects were still alive and active. Tests
were also conducted with sprayed glass plates that were dusted lightly
with flour. Confused flour beetle adults were exposed on these surfaces
for 1, 6, and 24 hours. Deposits of 50-mg. dosages of DDT and chlor-
dane from acetone-kerosene solutions failed to give a complete kill of
the beetles at any of the three exposures. Spray deposits of DDT wet-
table powder at the same rate gave a complete kill with the 24-hour
exposure, but not with the 1- and 6-hour exposures. Similar spray
deposits on undusted glass plates gave complete kills with 1-hour ex-
posure (table 1).
The light coating of flour on the glass plates was removed by brush-
ing lightly with a soft-bristle brush, and the efficiency of the spray
residues against the flour beetle tested once again. The efficiency of
the DDT wettable-powder deposits was apparently restored. However,
some of the deposits of DDT and chlordane in acetone-kerosene solution







-8-


were apparently removed by the brushing, since 100 percent kill was
not obtained at all exposures tried. Evidently sweeping sprayed sur-
faces reduces the efficiency of the residual deposits by removing them
mechanically.

Influence of Emulsifiers and Wetting Agents

In the tests described the various formulations were prepared in a
uniform manner in order to avoid differences due to composition. A
number of other tests, however, were made with formulations in which
different emulsifying agents were used. In these tests the emulsions
varied considerably in effectiveness. The wettable powders obtained
from commercial sources differed noticeably in their physical char-
acteristics. It seems likely that the effectiveness of these powders
may be influenced by the diluent or the wetting agent used. The DDT
wettable powder compared favorably with other formulations, whereas
the wettable powders of other materials were not all so efficient as the
corresponding emulsion formulations.

Precautions

ALL THESE RESIDUAL SPRAYS ARE POISONOUS TO WARM-
BLOODED ANIMALS. Parathion is the most toxic, followed in descend-
ing order by chlorinated camphene, gamma benzene hexachloride, DDT,
chlordane, TDE, and methoxychlor.
THE SPRAYS MUST NOT BE ALLOWED TO COME IN CONTACT
WITH ANIMAL FEEDS OR HUMAN FOOD. In solution in organic sol-
vents the insecticides are readily absorbed through the skin; therefore,
extensive exposure of the skin to such solutions should be avoided by
workmen applying them. Chlorinated camphene and gamma benzene
hexachloride in powder form can also be absorbed through the skin;
operators handling materials containing them should avoid continuous
direct contact or wearing clothes impregnated with the dusts.

Effect of Piperonyl Butoxide-Pyrethrum Formulations

Interest in the possible use of spray materials less toxic to warm-
blooded animals than the materials already discussed led to an investi-
gation of the efficacy of pyrethrum, piperonyl butoxide, and various
combinations of these materials as residual insecticides against the
confused flour beetle. Piperonyl butoxide reportedly has a synergistic
action on pyrethrum extract when mixed with it in insecticidal sprays.






-9-


Sprays containing these materials were applied to glass, metal,
and soft pine wood plates in the same manner as in the experiments
with the other chemicals. The following emulsion-concentrates were
formulated in refined kerosene oil to make 100 ml.:

Grams
1. Pyrethrum extract containing 20 percent of
pyrethrins - - - - - - - 40
Emulsifier - - - - - - - 12.5

2. Technical piperonyl butoxide - - - 10
Emulsifier - - - - - - - 12.5

3. Pyrethrum extract containing 20 percent of
pyrethrins - - - - - - - 5
Technical piperonyl butoxide - - - 10
Emulsifier - - - - - - - 12.5
The emulsion concentrates were diluted with water to provide the
concentration of spray residues desired.
In tests with emulsions containing pyrethrins alone as the toxicant
the residue from as little as 2 mg. of pyrethrins per 1/4 square foot
gave a complete kill of confused flour beetle adults exposed for 24
hours on glass plates that had been allowed to dry for 24 hours before
the beetles were confined on them. In similar tests with emulsions
containing piperonyl butoxide alone a dosage of 200 mg. of the butoxide
per 1/4 square foot of glass surface was required to give a 100 percent
kill of the adults with a 24-hour exposure. When the third formula was
used the addition of piperonyl butoxide to the pyrethrins in the propor-
tion of 10 to 1 by weight slightly improved the residual insecticidal
action of the pyrethrins
The results of tests on metal surfaces were almost identical with
those obtained on glass surfaces.
On soft pine wood plates the residues from dosages of 40 mg. of
pyrethrins alone and from 200 mg. of piperonyl butoxide alone failed
to kill all the flour beetle adults that were confined on the plates for
24 hours beginning 24 hours after the sprays were applied. The addi-
tion of piperonyl butoxide to the pyrethrins in the proportion of 10 to 1 by
weight failed to improve the insecticidal action of the pyrethrins.






-10-


Table 1.-Toxicity and speed of action of residual sprays against adult confused
flour beetles. Deposits on glass plates from dosage of 50 mg. per 1/4 square
foot.

Percent mortality at various intervals after exposure
Insecticide
formulation 1/2-hour exposure 1-hour exposure

2 4 6 8 10 12 2 4 6 8 110 12
days days I days days day Idays days days days days days days


Carbon tetrachloride sc
Chlordane
DDT
Gamma benzene
hexachloride
TDE
Methoxychlor
Chlorinated camphene

Xylene emulsions:
Chlordane
DDT
Gamma benzene
hexachloride
TDE
Methoxychlor
Chlorinated camphene


)lutions:
17 63
17 83


100
100


100
47
0
0


67 100
87 100


100
50
53
83


97
70
100


97 100
80 87


23 30 30
10 10 10


Wettable-powder suspensions:
Chlordane 0
DDT 0 1


Gamma benzene
hexachloride
TDE
Methoxychlor
Chlorinated camphene
Parathion


3 3 3
90 97 100


0 63
0 0
0 0
0 0
100


Acetone-kerosene solutions:
Chlordane 0
DDT 0
Gamma benzene
hexachloride 0
TDE 0
Methoxychlor 0
Chlorinated camphene 0


100
3
33
10


10 27 40 53
83 87 90 100


3 0
0


0
0
0
0
100


0
0

0
0
0
0


3 10
97 100


17 17


100
20
50
27


0 17 20 30 40
47 77 90 93 93


90 100
93 100


100
70
17
7


100
17
10


100


90
100

100
67
60
83


90
80
100


100
90


93 100






-11 -


Percent mortality at various intervals after exposure

3-hour exposure 6-hour exposure 24-hour exposure i/
2 4 6 8 10 12 2 4 6 8 10 12 2 4 6 8
days days days days days days days days days days days days days days days days


17 77 100
37 97 100


40 97 100
33 93 100


0 100 13 100 80 100
0 47 100 3 93 100 90 100
0 63 67 73 77 80 0 80 100 70 100
0 7 10 10 10 10 10 53 63 67 73 73 57 100


0 100
0 100

70 100
0 63 100
0 77 87 93
0 100


0 100
67 100

70 100
0 87 100
93 100 63 100
60 100


0 0 57 77 90 90
0 37 100

0 100
0 0 33 40 50 53
0 0 67 77 83 83
0 33 73 73 73 73
100


0 20 63 80 93 97
47 100


67 100
80 100

100
80 100
100
83 100


7 87 93 1CJ
47 100


0 100 90 100
0 50 57 60 60 60 40 100
0 10 90 93 93 97 7 97 97 100
0 0 63 67 73 87 53 97 100
100 100


0 47 67 100
0 73 97 100

0 63 70 73 77 80
0 27 40 40 40 47
0 3 10 13 17 23
0 0 33 40 43 43


0 67 87 100.
0 80 100


0 83 83 97 97 97
0 60 90 100
0 33 33 37 40 40
0 40 67 83 93 97


70 97 100
87 100

97 100
97 100
40 40 43
73 93 100


53 100
77 100


/ The mortality caused by the acetone-kerosene solution of methoxychlor was
47 percent 10 days after the 24-hour exposure and 50 percent 12 days thereafter.








-12-


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-13-


Table 3.-Toxicity and speed of action of residual sprays containing DDT,
chlordane, or chlorinated camphene against larvae of the confused flour
beetle. Deposits of carbon tetrachloride solutions on glass plates.


Insecticide and Dosage Exposure


Mg. per 1/4 sq. ft.


DDT:
50

30

10

5

2.5

1

Chlordane:
50

30

10


Chlorinated camphene:
50

30

"10


Hours


6
24
6
24
6
24
6
24
6
24
6
24


Period required for
Maximum mortality maximum mortality


Percent


Days


67
100
70
97
90
100
30
80
20
70
6
40


90
100
S77
100
57
97


80
100
67
100
33
93






-14-


Summary

Tests were made to determine the toxicity, speed of action, and dura-
tion of effectiveness against the confused flour beetle (Tribolium confusum
Duv.) of residual deposits from various formulations of DDT, chlordane,
chlorinated camphene, TDE, methoxychlor, gamma benzene hexachlo-
ride, parathion, piperonyl butoxide, and pyrethrum on various surfaces.
Parathion was the most toxic and killed the fastest of any compound
tested, although this material was tested only as a wettable-powder
spray. DDT, gamma benzene hexachloride, and chlordane were next in
order of toxicity when adult beetles were exposed to them for from 30
minutes to 24 hours. In general, the xylene emulsions were uniformly
more efficient and more rapid in action than the corresponding sus-
pensions or the carbon tetrachloride or acetone-kerosene solutions.
The latter solutions were the least effective and slowest in rate of kill
of all the formulations tested. DDT in all formulations and chlorinated
camphene in suspensions and in carbon tetrachloride solutions remained
effective on glass surfaces for more than a year. Chlordane, gamma
benzene hexachloride, TDE, and methoxychlor remained effective for
much shorter periods.
The effectiveness of residual sprays decreased with the increase in
the absorptiveness of the surface sprayed. Their effectiveness also
varied with the chemical composition of the surface. On cement sur-
faces the duration of effectiveness of all spray deposits was very short.
Pretreatment of cement with a sealer, magnesium-zinc-silicofluoride,
greatly improved the efficiency of spray deposits. On freshly painted
wood surfaces the type of finish influenced the effectiveness of the spray
deposit. Cold-water and flat oil paint greatly reduced the effectiveness
of the spray deposits but enamel did not. Water suspensions of wettable
powders were absorbed less than other formulations, so that on absorp-
tive surfaces, such as cement and cardboard, and on painted wood sur-
faces, they were more effective.
Chlordane and gamma benzene hexachloride deposits are volatile
and vapors given off killed the confused flour beetles. These fumiga-
tion and contact effects were about equal and persisted for about the
same -,ngth of time.
Temperature and light affect the duration of effectiveness of
residual spray deposits. Chlordane and gamma benzene hexachloride
deposits retained their effectiveness longer when stored at low tem-
peratures, and storage in darkness lengthened the period of effective-
ness of chlordane, gamma benzene hexachloride, methoxychlor, and
TDE.
Five milligrams of DDT per 1/4 square foot was found to be the low-
est effective dosage for use against confused flour beetle adults.






-15-


Eggs and pupae of the confused flour beetle were not materially
affected by exposure on surfaces bearing spray residues. Larvae
were affected but were much more resistant than the adults. Heavier
dosages were required to kill the larvae and a longer period was re-
quired for the dosages to take effect.
A coating of flour dust reduced the effectiveness of spray deposits
and when flour was swept from surfaces a portion of the spray deposit
was removed.
Observations indicate that the emulsifying and wetting agents em-
ployed in the manufacture of spray formulations may materially effect
their efficiency.
Residues from pyrethrum extracts were effective against flour
beetle adults confined on glass and metal surfaces 24 hours after the
sprays were applied, but were not effective on soft pine wood surfaces
The efficiency of piperonyl butoxide residues against the confused flour
beetle was very low, and the addition of piperonyl butoxide did not
materially increase the toxicity of the pyrethrins to the beetles on glass
or metal surfaces.
This report is not intended as a recommendation of any particular
material or formulation for commercial use.




UNIVERSITY OF FLORIDA
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3 1262 09239 1944