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The behaviour of Tribolium castaneum (Herbst) and Sitophilus granarius (L.) in the presence of insecticide-treated surfaces
J. srored Prod. Res. 1977. Vol. 13. 145-148. Pergamon
SHORT
THE BEHAVIOUR
in Great Britain.
Press. Printed
COMMUNICATION
CASTANEUM (HERBST) AND (L.) IN THE PRESENCE OF INSECTICIDE-TREATED SURFACES
SZTOPHILUS
OF TRZBOLIUM GRANARIUS
INTRODUCTION
directed attention to the practical problem of the survival of apparently thorough insecticide treatments by stored-products insects. His laboratory tests with Tribolium castaneum (Herbst) demonstrated that survival can be attributed to the avoidance of contact with the insecticide by the beetles spending a greater proportion of time in uncontaminated refuges containing food. In his experiments. as in the practical situation, the insects were able to respond to several environmental factors including food, shelter, insecticide and insecticide carrier. In the present experiments some of these factors were eliminated. A simple method has been developed to determine whether stored-products beetles avoid surfaces treated with particular insecticides. PINNIGER
(1974,
1975)
MATERIALS
AND METHODS
A two-choice arena was set up in which the insects could be either on the half treated with insecticide or on the untreated half. Whatman No. 1 filter papers (70 mm dia) were either treated with 0.5 ml of a solution of insecticide in a 3: 1 mixture by volume of petroleum ether (6&8O“C b.p.) and acetone. or with 0.5 ml of the solvent mixture alone, applied by pipette. They were left overnight to dry and then cut into halves. Each treated half was abutted to an untreated half on a flat glass plate. to form the floor of the arena. The insects were confined to the filter paper by a glass ring 50 mm dia by 25 mm high, coated on the inside with non-stick polytetrafluoroethylene (P.T.F.E.) suspension. The confinement took place in the dark except for brief periods of illumination during observations. The outside of the glass ring was painted matt black and the ring and its filter paper floor were enclosed in a matt black cylinder 70 mm dia by 150 mm high. Four observation holes, 5 mm dia, were cut in the top and three triangles, 20 mm high, were cut out of the base to prevent the accumulation of insecticide vapours (Fig. 1). A 1 W bulb attached to the centre of the inside of the top of the cylinder provided =.
‘\
Filter
\
Observation
\
Light
paper hole
bulb
-Cylinder , Ventilation
hole
Gloss ring Filter
papet
Gloss plate
FIG. I, Section
through 145
experimental
;wena
146
SHORT COMMUNICATION
illumination only during observations. The observation holes were covered by a black filter paper when not in use. Vibration of the table on which the arenas were placed was minimized by placing rubber bungs (60 mm dia by 50 mm high) under the legs. Unless indicated otherwise, 20 arenas were used at a time. To avoid unknown directional effects, the arenas were arranged in 5 groups of 4; in each group the filter papers were positioned to have the border between the treated and untreated halves running in the same direction in two arenas, and at right angles to this in the other two; and in each of these pairs of arenas the treated half was on opposite sides. Ten adult insects of undetermined sex were introduced to the centre of each arena and the numbers on the treated and untreated sides were counted after 3 and 6 hr. Each test was repeated with different insects from the same culture on a different day. The insecticide concentrates used were pyrethrins (99”/J, bioresmethrin (939,), lindane (100%). DDT (lOO”/O),malathion (95%), pirimiphos-methyl (8610 and chlorpyrifosmethyl (97%). The filter papers were treated with the highest dose that did not produce observable toxic effects on the insects. The insects used were Sitophilus granarius (L.) WS-strain and Tribolium castaneum FSS-strain, both laboratory strains with no known resistance to insecticides; and T. castaneum CTC12, a strain with a wide spectrum of insecticide resistance including organophosphates, organochlorines and pyrethroids (Champ & Campbell-Brown, 1970). All insects were bred and tested at 25°C and 70:/g r.h. The S. granarius adults were tested when 2-4 weeks old and the T. castaneum when 3-5 weeks old. RESULTS
The results of the 3 and 6 hr counts were similar but the responses were less pronounced in the former. The results of the 6 hr counts are summarised in Tables 1 and 2. The data was subjected to a t test to determine any significant differences in the deviations from the expected mean number of five on each side of the arena. S. granarius (Table 1) showed no significant differences. Both strains of T. castaneum (Table 2) showed significantly fewer numbers than expected on the sides treated with pyrethrins, bioresmethrin, lindane and DDT, the FSS strain on pirimiphos-methyl approached a significant difference (P - 0.05). There were no significant differences in the other tests with T. castaneum. The results of both S. granarius and T. castaneum tests were shown to follow closely a Poisson distribution when Fisher’s exact test for heterogeneity was applied (Fisher, 1950). The expected nil response is equal numbers of insects on the treated and untreated
TABLE
1. NUMBER
Insecticide
(PER 10) OF Sitophilus grarmrius ON THE TREATED SIDE OF THE ARENA AFTER INTRODUCTION*
Concn. (Pb)
Pyrethrins
0.2
Bioresmethrin
0.05
DDT
0.5
Lindane
0.01
Malathion
0.005
Pirimiphos-methyl
0.01
Chlorpyrifos-methyl
0.005
No. on treated side Mean + S.E. 4.40 4.89 5.45 5.00 4.55 4.45 4.65 4.15 5.55 4.70 4.80 4.65 5.35 5.60
* f + + + + k + * * k f + k
0.40 0.43 0.51 0.41 0.41 0.39 0.32 0.49 0.44 0.39 0.54 0.33 0.47 0.48
* Twenty arenas were used for each testing giving 19 degrees t Eighteen arenas used giving 17 degrees of freedom.
of freedom
~HR
(19td.f.,
P
1.50 0.26t 0.88
0.15 0.79 0.39
1.09 1.40 1.10 0.51 1.26 0.77 0.37 1.05 0.75 1.24
0.29 0.17 0.29 0.62 0.22 0.46 0.1’ 0.3 1 0.47 0.23
in the I test.
SHORT COMMUNICATION
TABI.E 2. NChlBER
(PER
10)
OF
Tribolium
castaneum ON
THE
147
TREATED
SIDE OF THE
ARENA
~HR
AFTER
INTRODUCTION*
Insecticide: Pyrethins Bioresmethrin DDT Lmdane Malathion Pirimiphos-methyl Chlorpyrifos-methyl
Susceptible strain FSS No. on treated side Mean k SE. (19td.f.l 0.60 + 0.18 1.55 f 0.37 3.50 * 0.49 1.40 _t 0.28 3.65 + 0.44 2.21 + 0.39 0.85 + 0.26 0.65 f 0.18 5.50 & 0.34 4.60 + 0.48 3.85 + 0.47 4.05 + 0.53 5.95 + 0.51 5.70 + 0.38
23.97 9.42 3.07 12.65 3.09 7.21t 15.70 23.94 1.45 0.83 2.47 1.77 1.88 1.8’
P io.001 io.001 0.006 io.001 0.006
Resistant strain CTC 12 No. on treated side Mean f S.E. (19td.f.l 0.60 i 2.05 f 1.80 + 2.50 * 3.95 * 3.95 * 2.65 k 3.65 f 5.00 + 5.10 * 4.55 + 4.70 f 5.15 * 5.75 *
0.17 0.33 0.40 0.55 0.47 0.52 0.36 0.48 0.47 0.43 0.32 0.49 0.50 0.49
P
26.10 8.99 7.97 4.51 2.25 2.02 6.44 2.80
< 0.001
0.23 1.41 0.6 I 0.30 1.53
0.82 0.17 0.56 0.76 0.1-l
* Twenty arenas were used for each testing giving 19 degrees of freedom in the r test. t Nineteen arenas used giving 18 degrees of freedom. 2 Dose rates as in Table I.
sides of the arenas (a mean of 5 per side). A mean of <4 or >6 is required the deviation from the expected nil response is significant.
before
DISCUSSION
The results of these preliminary experiments show that T. castuneum may avoid a broad spectrum of commercially available insecticidal compounds at dose levels which do not cause avoidance in S. granarius. Although the insects were generally stationary when counted, the method will not distinguish a tendency not to cross the border between the treated and the untreated paper. from faster movement on the treated side. The nil responses may have occurred because of a general unresponsiveness to the compound, or the use of concentrations below the threshold level of response. The avoidance by T. castaneum of pyrethrins, bioresmethrin, lindane and DDT was consistent both between tests and between strains, which suggests that it was unconnected with the biochemical resistance of the CTC12 strain. In the present experiment, T. castaneum exhibited nil response to malathion whereas Pinniger (1975) found significantly more T. castaneum in refuges with food that were surrounded by an arena treated with 800mg/m2 malathion wettable powder (active ingredient) than in refuges in an untreated arena. His dosage, equivalent to a practical treatment. was 123 times greater than that used in the present experiment. The effect of the carrier powder was unknown. In both Pinniger’s and the present experiments, T. castaneum may have secreted quinones. which are repellent to both sexes (Loconti & Roth, 1953) particularly in the presence of the insecticides and thereby reinforced the behavioural responses noted. The ranking of the insecticides in terms of avoidance does not concur with the ranking of the physical factors of molecular weight, molecular concentration, or vapour pressure. Too few compounds were used to draw conclusions from the chemical groupings except that T. casfaneum avoided the pyrethroids and organochlorines, but not the organophosphates. Ministq~ qf Agriculture, Fisheries and Food, Pest lf~festation Control Laboratory, London Road, slough, Berks, England
A. J. F’RICKETT C. A. RATCLIFFE
148
SHORT COMMUNICATION
REFERENCES CHAMP, B. R. and CAMPBELL-BROWN, M. J. (1970) Insecticide resistance in Australian Tribolium custarwum (Herbst) (Coleoptera, Tenebrionidae)-II. Malathion resistance in Eastern Australia. J. stored Prod. Res. 6, 111-131. FISHER, R. A. (1950) The significance of deviations from expectation in a Poisson series. Biometrics 6, 17-24. LOCONTI, J. D. and ROTH. L. M. (1953) Composition of the odorous secretion of Tribolium castaneum. Ann. ent. Sot. Amer. 46, 28lL289. PINNIGER, D. B. (1974) A laboratory simulation of residual populations of stored product pests and an assessment of their susceptibility to a contact insecticide. J. stored Prod. Res. 10, 217-223. PINNIGER. D. B. (1975) The behaviour of insects in the presence of insecticides: the effect of fenitrothion and malathion on resistant and susceptible strains of Triholium custuneum (Herbst). Proc. 1st int. Wkg Conf. Stored-Prod. Ent.. Savannah 1974. pp. 301-308.
SHORT
THE BEHAVIOUR
in Great Britain.
Press. Printed
COMMUNICATION
CASTANEUM (HERBST) AND (L.) IN THE PRESENCE OF INSECTICIDE-TREATED SURFACES
SZTOPHILUS
OF TRZBOLIUM GRANARIUS
INTRODUCTION
directed attention to the practical problem of the survival of apparently thorough insecticide treatments by stored-products insects. His laboratory tests with Tribolium castaneum (Herbst) demonstrated that survival can be attributed to the avoidance of contact with the insecticide by the beetles spending a greater proportion of time in uncontaminated refuges containing food. In his experiments. as in the practical situation, the insects were able to respond to several environmental factors including food, shelter, insecticide and insecticide carrier. In the present experiments some of these factors were eliminated. A simple method has been developed to determine whether stored-products beetles avoid surfaces treated with particular insecticides. PINNIGER
(1974,
1975)
MATERIALS
AND METHODS
A two-choice arena was set up in which the insects could be either on the half treated with insecticide or on the untreated half. Whatman No. 1 filter papers (70 mm dia) were either treated with 0.5 ml of a solution of insecticide in a 3: 1 mixture by volume of petroleum ether (6&8O“C b.p.) and acetone. or with 0.5 ml of the solvent mixture alone, applied by pipette. They were left overnight to dry and then cut into halves. Each treated half was abutted to an untreated half on a flat glass plate. to form the floor of the arena. The insects were confined to the filter paper by a glass ring 50 mm dia by 25 mm high, coated on the inside with non-stick polytetrafluoroethylene (P.T.F.E.) suspension. The confinement took place in the dark except for brief periods of illumination during observations. The outside of the glass ring was painted matt black and the ring and its filter paper floor were enclosed in a matt black cylinder 70 mm dia by 150 mm high. Four observation holes, 5 mm dia, were cut in the top and three triangles, 20 mm high, were cut out of the base to prevent the accumulation of insecticide vapours (Fig. 1). A 1 W bulb attached to the centre of the inside of the top of the cylinder provided =.
‘\
Filter
\
Observation
\
Light
paper hole
bulb
-Cylinder , Ventilation
hole
Gloss ring Filter
papet
Gloss plate
FIG. I, Section
through 145
experimental
;wena
146
SHORT COMMUNICATION
illumination only during observations. The observation holes were covered by a black filter paper when not in use. Vibration of the table on which the arenas were placed was minimized by placing rubber bungs (60 mm dia by 50 mm high) under the legs. Unless indicated otherwise, 20 arenas were used at a time. To avoid unknown directional effects, the arenas were arranged in 5 groups of 4; in each group the filter papers were positioned to have the border between the treated and untreated halves running in the same direction in two arenas, and at right angles to this in the other two; and in each of these pairs of arenas the treated half was on opposite sides. Ten adult insects of undetermined sex were introduced to the centre of each arena and the numbers on the treated and untreated sides were counted after 3 and 6 hr. Each test was repeated with different insects from the same culture on a different day. The insecticide concentrates used were pyrethrins (99”/J, bioresmethrin (939,), lindane (100%). DDT (lOO”/O),malathion (95%), pirimiphos-methyl (8610 and chlorpyrifosmethyl (97%). The filter papers were treated with the highest dose that did not produce observable toxic effects on the insects. The insects used were Sitophilus granarius (L.) WS-strain and Tribolium castaneum FSS-strain, both laboratory strains with no known resistance to insecticides; and T. castaneum CTC12, a strain with a wide spectrum of insecticide resistance including organophosphates, organochlorines and pyrethroids (Champ & Campbell-Brown, 1970). All insects were bred and tested at 25°C and 70:/g r.h. The S. granarius adults were tested when 2-4 weeks old and the T. castaneum when 3-5 weeks old. RESULTS
The results of the 3 and 6 hr counts were similar but the responses were less pronounced in the former. The results of the 6 hr counts are summarised in Tables 1 and 2. The data was subjected to a t test to determine any significant differences in the deviations from the expected mean number of five on each side of the arena. S. granarius (Table 1) showed no significant differences. Both strains of T. castaneum (Table 2) showed significantly fewer numbers than expected on the sides treated with pyrethrins, bioresmethrin, lindane and DDT, the FSS strain on pirimiphos-methyl approached a significant difference (P - 0.05). There were no significant differences in the other tests with T. castaneum. The results of both S. granarius and T. castaneum tests were shown to follow closely a Poisson distribution when Fisher’s exact test for heterogeneity was applied (Fisher, 1950). The expected nil response is equal numbers of insects on the treated and untreated
TABLE
1. NUMBER
Insecticide
(PER 10) OF Sitophilus grarmrius ON THE TREATED SIDE OF THE ARENA AFTER INTRODUCTION*
Concn. (Pb)
Pyrethrins
0.2
Bioresmethrin
0.05
DDT
0.5
Lindane
0.01
Malathion
0.005
Pirimiphos-methyl
0.01
Chlorpyrifos-methyl
0.005
No. on treated side Mean + S.E. 4.40 4.89 5.45 5.00 4.55 4.45 4.65 4.15 5.55 4.70 4.80 4.65 5.35 5.60
* f + + + + k + * * k f + k
0.40 0.43 0.51 0.41 0.41 0.39 0.32 0.49 0.44 0.39 0.54 0.33 0.47 0.48
* Twenty arenas were used for each testing giving 19 degrees t Eighteen arenas used giving 17 degrees of freedom.
of freedom
~HR
(19td.f.,
P
1.50 0.26t 0.88
0.15 0.79 0.39
1.09 1.40 1.10 0.51 1.26 0.77 0.37 1.05 0.75 1.24
0.29 0.17 0.29 0.62 0.22 0.46 0.1’ 0.3 1 0.47 0.23
in the I test.
SHORT COMMUNICATION
TABI.E 2. NChlBER
(PER
10)
OF
Tribolium
castaneum ON
THE
147
TREATED
SIDE OF THE
ARENA
~HR
AFTER
INTRODUCTION*
Insecticide: Pyrethins Bioresmethrin DDT Lmdane Malathion Pirimiphos-methyl Chlorpyrifos-methyl
Susceptible strain FSS No. on treated side Mean k SE. (19td.f.l 0.60 + 0.18 1.55 f 0.37 3.50 * 0.49 1.40 _t 0.28 3.65 + 0.44 2.21 + 0.39 0.85 + 0.26 0.65 f 0.18 5.50 & 0.34 4.60 + 0.48 3.85 + 0.47 4.05 + 0.53 5.95 + 0.51 5.70 + 0.38
23.97 9.42 3.07 12.65 3.09 7.21t 15.70 23.94 1.45 0.83 2.47 1.77 1.88 1.8’
P io.001 io.001 0.006 io.001 0.006
Resistant strain CTC 12 No. on treated side Mean f S.E. (19td.f.l 0.60 i 2.05 f 1.80 + 2.50 * 3.95 * 3.95 * 2.65 k 3.65 f 5.00 + 5.10 * 4.55 + 4.70 f 5.15 * 5.75 *
0.17 0.33 0.40 0.55 0.47 0.52 0.36 0.48 0.47 0.43 0.32 0.49 0.50 0.49
P
26.10 8.99 7.97 4.51 2.25 2.02 6.44 2.80
< 0.001
0.23 1.41 0.6 I 0.30 1.53
0.82 0.17 0.56 0.76 0.1-l
* Twenty arenas were used for each testing giving 19 degrees of freedom in the r test. t Nineteen arenas used giving 18 degrees of freedom. 2 Dose rates as in Table I.
sides of the arenas (a mean of 5 per side). A mean of <4 or >6 is required the deviation from the expected nil response is significant.
before
DISCUSSION
The results of these preliminary experiments show that T. castuneum may avoid a broad spectrum of commercially available insecticidal compounds at dose levels which do not cause avoidance in S. granarius. Although the insects were generally stationary when counted, the method will not distinguish a tendency not to cross the border between the treated and the untreated paper. from faster movement on the treated side. The nil responses may have occurred because of a general unresponsiveness to the compound, or the use of concentrations below the threshold level of response. The avoidance by T. castaneum of pyrethrins, bioresmethrin, lindane and DDT was consistent both between tests and between strains, which suggests that it was unconnected with the biochemical resistance of the CTC12 strain. In the present experiment, T. castaneum exhibited nil response to malathion whereas Pinniger (1975) found significantly more T. castaneum in refuges with food that were surrounded by an arena treated with 800mg/m2 malathion wettable powder (active ingredient) than in refuges in an untreated arena. His dosage, equivalent to a practical treatment. was 123 times greater than that used in the present experiment. The effect of the carrier powder was unknown. In both Pinniger’s and the present experiments, T. castaneum may have secreted quinones. which are repellent to both sexes (Loconti & Roth, 1953) particularly in the presence of the insecticides and thereby reinforced the behavioural responses noted. The ranking of the insecticides in terms of avoidance does not concur with the ranking of the physical factors of molecular weight, molecular concentration, or vapour pressure. Too few compounds were used to draw conclusions from the chemical groupings except that T. casfaneum avoided the pyrethroids and organochlorines, but not the organophosphates. Ministq~ qf Agriculture, Fisheries and Food, Pest lf~festation Control Laboratory, London Road, slough, Berks, England
A. J. F’RICKETT C. A. RATCLIFFE
148
SHORT COMMUNICATION
REFERENCES CHAMP, B. R. and CAMPBELL-BROWN, M. J. (1970) Insecticide resistance in Australian Tribolium custarwum (Herbst) (Coleoptera, Tenebrionidae)-II. Malathion resistance in Eastern Australia. J. stored Prod. Res. 6, 111-131. FISHER, R. A. (1950) The significance of deviations from expectation in a Poisson series. Biometrics 6, 17-24. LOCONTI, J. D. and ROTH. L. M. (1953) Composition of the odorous secretion of Tribolium castaneum. Ann. ent. Sot. Amer. 46, 28lL289. PINNIGER, D. B. (1974) A laboratory simulation of residual populations of stored product pests and an assessment of their susceptibility to a contact insecticide. J. stored Prod. Res. 10, 217-223. PINNIGER. D. B. (1975) The behaviour of insects in the presence of insecticides: the effect of fenitrothion and malathion on resistant and susceptible strains of Triholium custuneum (Herbst). Proc. 1st int. Wkg Conf. Stored-Prod. Ent.. Savannah 1974. pp. 301-308.