Topical and Oral Toxicity of Sulfluramid, a Delayed-Action Insecticide, Against the German Cockroach (Dictyoptera: Blattellidae) B. L. REID, G. W. BENNETT, ANDS. J. BARCA Y Department
of Entomology,
J.
Purdue University, West Lafayette,
Indiana 47907
Econ. Entomol. 83(1): 148-152 (1990)
The LD50of sulfluramid topically applied to 2-d-old, fifth instars of the German cockroach, Blattella germanica (L.), was estimated at 14.5 p.g/g (95% FL = 13.7-15.4 p.g/ g). Sulfluramid was significantly more toxic than topically applied hydramethylnon (LD50 = 29.2 [19.0-46.5] p.g/g). Sulfluramid had delayed toxicity but caused mortality significantly faster than hydramethylnon after topical application. The oral LD50 against newly eclosed, fifth instars was estimated to be 4.1 (3.9-4.4) p.g/g; this toxicity was significantly greater than when sulfluramid was topically applied. Mortality caused by sulfluramid occurred significantly more slowly in the dietary exposures than in the topical applications. Sulfluramid at 1,000 ppm in diets was not a feeding deterrent to nymphal B. germanica. ABSTRACT
Insecta, Blattella germanica, sulfluramid, delayed-action
TOXIC FOOD BAITShave been a successful management tool for the control of several insect species, including red imported fire ant, Solenopsis invicta Buren, and Pharaoh ant, Monomorium pharaonis (L.). This treatment strategy has many advantages related to minimizing environmental contamination. Use of bait formulations typically results in less chemical use. Toxicants can be placed in more discrete areas than is possible with conventional spray treatments. If the bait base is most attractive to the target pest species, some species specificity can be achieved so that risks to nontarget organisms are reduced. For these reasons, use of toxic baits may be compatible with environmentally sound integrated pest management programs. Use of toxic baiting in the control of cockroaches has a long and varied history (Frishman 1982). Toxic baits containing phosphorous, boric acid, and other compounds were most effective against Periplaneta spp. and other large domiciliary cockroaches (Cheng & Campbell 1940, Lofgren & Burden 1958), but the more prevalent German cockroach, Blattella germanica (L.), was not successfully controlled with these products. German cockroaches were successfully controlled with baits containing chlordecone (Kepone) (Burden & Smittle 1975) for a short period of time before cancellation of their registrations by the Environmental Protection Agency during the late 1970s. Success and failure have been reported with 0.5% chlorpyrifos baits that are commonly available to consumers (Lund & Bennett 1978, Rust & Reierson 1981), but a high density of bait placements (>40 in two- or three-bedroom apartments) are required for effective population reduction. A major advance in control of the German cockroach and other cockroach species with toxic baits was the discovery of hydramethylnon (Lovell 1979). 0022-0493/90/0148-0152$02.00/0
toxicity
This compound is representative of a class of insecticides (amidinohydrazones) that inhibit mitochondrial electron transport (Hollingshaus 1987) and cause delayed mortality by disruption of respiratory energy production. The efficacy of hydramethylnon baits for cockroach control has been well documented (e.g., Bennett & Runstrom 1984, Reierson et al. 1982). The success of products containing hydramethylnon (Combat and Maxforce Roach Control System, American Cyanamid, Princeton, N.J.) has stimulated research on the strategy of controlling cockroaches with toxic baits. Sulfluramid (N-ethyl perfluorooctane sulfonamide) is a potential bait toxicant that belongs to a new class of delayed-action insecticides, the fluoroaliphatic sulfonamides (Vander Meer et al. 1985). Cross & Schnellmann (1989) showed that sulfluramid is an uncoupler of oxidative phosphorylation. In the research reported here, we compared the toxicity of sulfluramid to hydramethylnon in topical applications and evaluated its activity as a stomach poison in dietary feeding studies. The possibility of feeding deterrence associated with its presence in a food source also was examined.
Materials and Methods Blattella germanica used in this research were from a Johnson Wax strain, nonresistant to conventional insecticides (Koehler & Patterson 1986), that were maintained throughout these studies under a photoperiod of 12:12 (L:D) at 28 ± 1°e. Test insects were nymphs (fifth instar) that were obtained by establishing large groups of late fourth instars with water and harborage but no food. Thereafter, individuals found within these groups' that had molted to the fifth instar were easily dis-
© 1990 Entomological Society of America
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
KEY WORDS
February
1990
REID ET AL.: TOXICITY
OF SULFLURAMID
149
Six replicates with 10 newly ec10sed fifth instars were conducted for each of eight diet concentrations (7.8, 15.6, 31.3, 62.5, 125, 250, 500, and 1,000 ppm). Insects were established with toxic diets within 24 h of their molt to the fifth instar and were forced to consume one diet pellet before they were provided with untreated food; this typically took 2-3 d. Estimation of an oral LDso is based on the assumption that each cockroach consumed the same amount of diet (10 mg per insect) and adjusting for the weight of a 2-d-old fifth instar (approximately 35 mg). Results of the conversion of diet concentrations to oral doses were 2.2, 4.5, 8.9, 17.9,35.7,71.4,142.9, and 285.7 ~g/g. Mortality was recorded daily for 5 d after introduction of the toxic diets and once more when all surviving insects had reached adulthood (approximately 14 d). The oral LDso value for sulfluramid was estimated by regression analysis of the probit mortality to the adult stage versus loglO of dose. The LTso's for 1,000 and 500 ppm sulfluramid diets were estimated from the regression of the cumulative daily probit mortality versus loglo of time (d). SAS software (SAS Institute 1985) was used for both estimation procedures. L Tor LDso's with 95% FL that did not overlap were considered significantly different. Feeding Deterrence. The possibility of feeding avoidance resulting from the presence of sulfluramid in the only food available to the test insects was examined with a computerized Moving-Image-Analyzer modified by Barcay (1986) from the Spider Tracking Program described by Hoy et a!. (1983). This system monitors, records, and analyzes the movement behavior of individual insects within a Plexiglas observation arena (30.5 cm diameter). A IOO-mg diet pellet, prepared as described above, was glued in the center of the arena with Elmer's Glue-All (Borden, Columbus). The image analysis programming defined an area immediately surrounding this diet; interactions of a test insect with the diet pellet were monitored. A moistened cotton wick was situated to provide a water source near the edge of the arena. This wick also offered a preferred site of harborage for the test insects, which would otherwise frequent the diet pellet to fulfill their thigmotactic habits (S.J.B., unpublished data). Thigmotactic orientation to the diet pellet would be an undesirable artifact for a method designed to compare feeding responses of the insects to varying diets. Newly ec10sed fifth instars were allowed to develop with food and water for 48 h, after which they were denied food for 24 h. This starving regime allowed a rigorous (although highly artificial) evaluation of possible feeding deterrence from the sulfluramid incorporated into diets. At the conc1usion of this starving regime, the insects were liberated into the observation arena for analysis of their behavioral interactions with the diet pellet. All studies were conducted under infrared illumination to simulate scotophase conditions.
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
tinguishable from their cohorts on a daily basis, and we were certain that they had molted within the previous 24 h. The absence of food ensured that these fifth instars had not yet fed, which was an important consideration in synchronous staging of the various ages used. In all experiments, test insects were housed in disposable plastic Petri dishes (100 by 25 mm) provided with harborage, water, and food. Topical Applications. Technical grade formulations of sulfluramid (98.0%; Lipha Chemicals, Milwaukee) and hydramethylnon (95.6%; American Cyanamid, Princeton, N.J.) were diluted in acetone and applied topically in 1-~1 droplets to the intercoxal regions of the meso- and meta thoracic regions of 2-d-old, fifth instars (x ± SEM = 34.8 ± 4.1 mg, n = 40). Solutions were prepared at six rates (3.1, 6.3, 12.5, 25, 50, and 100 ~g/g body weight) for each compound; an additional series was conducted for sulfluramid at six rates (8.2, 10.3, 12.8, 16, 20, and 25 ~g/g). Each treatment was administered to a total of 60 nymphs, which were grouped (10 insects per Petri dish) for observational purposes and supplied with food, water, and harborage. Mortality was recorded daily for 7 d and again when all surviving insects had reached adulthood (approximately 12 d after treatment). LDso's for sulfluramid and hydramethylnon were estimated by regression analysis of the probit mortality to the adult stage versus loglo of dose. The speed of action (LTso) for the 100- and 50-~g/g doses of each compound was estimated by regression of the cumulative daily probit mortality versus loglo of time (d). SAS software (SAS Institute 1985) was used for both estimation pr.ocedures. The criterion of nonoverlapping 95% FL was used to estimate significant differences. Dietary Studies. In studies of dietary activity, we did not compare hydramethylnon and sulfluramid. In preliminary rate determination studies, we observed a disparity in diet consumption: 1-2 d longer were required for insects to consume 100 mg of hydramethylnon diet (100 and 1,000 ppm) than insects feeding on sulfluramid diet. These observations suggested that differential feeding (hence, toxicant exposure) would invalidate a comparison of effects of hydramethylnon and sulfluramid consumed in diet. We evaluated dietary activity of sulfluramid with procedures developed by DeMark (1988). Experimental diets were prepared by finely grinding Wayne rodent blox (Continental Grain Company, Chicago), then reconstituting this media (5 g) with an appropriate acetone solution (3 ml) of sulfluramid and water (6 ml). The resulting mixture was thoroughly mixed, pressed into Plexiglas molds, and dried for 48 h within an evacuation hood to yield pelletized diets (x ± SEM = 100 ± 2 mg). All diets were stored (5°C) in glass Petri dishes lined with filter paper and containing cotton balls as a moisture absorbent.
TO NYMPHAL B. germanica
150
JOURNAL OF ECONOMIC
la: sulfluramid
ENTOMOLOGY
Vol. 83, no. 1
The LDso (95% FL) for sulfluramid was 14.5 (13.7-15.4) p.g/g. The regression had a slope (±SE) 100 of 5.86 ± 0.17 (n = 361 insects). Sulfluramid was - ...• slope was 5.99 ± 0.17 (n = 240 observations). At .•.. lU 25 100-p.g/g doses, sulfluramid caused mortality significantly more quickly than topically applied hydramethylnon (LTso = 3.23 [2.89-3.60] d). The slope ....• o for the regression estimating the speed of kill for a 100-/.Lg/g dose of hydramethylnon was 5.07 ± Ib: hydramethylnon 0.20 (n = 300 observations). The LT50 (95% FL) for a 50-/.Lg/g dose of sulfluramid was 1.88 (1.68100 2.12) d. The slope was 4.27 ± 0.23 (n = 300 observations). At 50-p.g/g doses, sulfluramid caused mortality significantly more quickly than topically .5 75 •..o applied hydramethylnon (LT:so= 6.89 [5.78-8.52] IS d). The slope for 50 p.g/g of hydramethylnon was 2.39 ± 0.42 (n = 300 observations). ~ 50 ClI Comparisons of the topical LDsoand LT:soshowed ;> ...• .•.. that sulfluramid was twice as toxic as hydramethyllU 25 non when applied topically to 2-d-old fifth instars of B. germanica and produced mortality in less ::l ....• than half the time required for hydramethylnon . o The L Tsoat 100 p.g/g for each compound indicated 1 2 3 4 5 6 7 adults that sulfluramid kills significantly faster than hydays after treatment dramethylnon. Differences between compounds at Fig. I. Cumulative percentage of mortality in 2-d- the LT50 were even greater at 50 p.g/ g, but the 50old, fifth-instar German cockroaches following topical /.Lg/ g rate of hydramethylnon failed to achieve 100% applications of one of six doses of either sulfluramid (a) mortality (Fig. 1b). The greater toxicity and faster or hydramethylnon (b) in 1 ILlof acetone. action of sulfluramid indicate a potential for improvements in cockroach bait products. Cockroach Data from 3-h trials with the Moving-Imagebait products containing hydra methyl non, alAnalyzer were recorded for one of two diet types: though highly effective control measures, can take from 2 to 4 wk after application before significant acetone blank controls or 1,000 ppm sulfluramid. Experiments with each type of diet were replicated reductions in infestations are detected (Bennett & Runstrom 1984, Reierson et al. 1982). with six insects. The time (min) to diet discovery, the time spent at the diet (interpreted as time of Dietary Studies. Results for cumulative mortality over time for sulfluramid in diet, like those in consumption), and number of visits to the diet were evaluated to test for feeding deterrence. Mean val- the topical applications (Fig. 1), indicated that ues were analyzed by two-tailed t tests (P = 0.05; mortality induced by sulfluramid continued to acSAS Institute 1985). cumulate for several days following exposure (Fig. 2). This trend was most evident at diet concentrations of 62.5 ppm (17.9 p.g/g) and 31.3 ppm (8.9 Results and Discussion /.Lg/g). At these concentrations, mortality after 5 d Topical Applications. Although the mortality was 10 and 0%, respectively, yet had risen to 100 and 95% when surviving insects reached caused by both compounds accumulated over time, mortality induced by sulfluramid occurred more adulthood. At 7.8 ppm (2.2 p.g/g), sulfluramid was not toxic. quickly (Fig. 1). At 100 p.g/g, all insects treated with sulfluramid died by 3 d, while hydramethylThe oral LD:so(95% FL) of sulfluramid fed to non-treated insects did not die until after 7 d. At test insects (n = 328) was 4.14 (3.90-4.40) p.g/g. 50 and 25 p.g/g, mortality caused by hydramethylThe slope of the regression was 5.85 ± 0.17. The non reached thresholds (53.3 and 38.0%, respecLTso (95% FL) for the 1,000-ppm diet (285.7 p.g/ tively) at 6 d, whereas all insects treated with sul- g) was 2.14 (1.94-2.35) d. The probit regression fluramid died by 5 d. Data from the 8.2-25 p.g/g had a slope of 6.62 ± 0.15 (n = 240). The L Tso topical doses of sulfluramid (plots not shown) in- (95% FL) for diet containing 500 ppm (142.9 p.g/ dicated that mortality continued to occur beyond g) was 3.27 (2.99-3.58) d. The probit regression had a slope of 7.71 ± 0.13 (n = 240). 8 d. dose (I!gl g)
3
'a §
'ae
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
:E
February 1990
REID ET AL.: TOXICITY OF SULFLURAMID TO NYMPHAL
100
dietary cone. (ppm)
~ ;;:
--2 o
~'"
75
Ei
~ 50 ell
...•> 1U 25 '3
Ei
e
151
1000.0 500.0 250.0 125.0 62.5 31.3 15.6 7.8
0
1 2 3 4 5 adults days of 5th stage Fig. 2. Cumulative percentage of mortality in newly eclosed fifth-instar German cockroaches following consumption of 100 mg of diet containing one of eight concentrations of sulfluramid. toxicant hydramethylnon suggests that highly effective baits for the control of German cockroaches and, presumably, other cockroach species can be developed. In addition, our tests did not indicate feeding avoidance by nymphal German cockroaches to sulfluramid, which was present in the only food available; thus, feeding deterrence should not be an impediment to the development of toxic bait with sulfluramid. Delayed mortality associated with sulfluramid exposure should be especially important in the control of social insects (Vander Meer et al. 1985), in which trophallaxis from exposed individuals can spread toxicants throughout colonies. Acknowledgment We thank J. Neal and J. Owens for their critical review of early drafts of this manuscript and A. Las and A. Nethery for their technical supJXlrt.We acknowledge the partial financial support of this research by Lipha Chemical Co. This article is journal paper 11,857, Purdue University Agricultural Experiment Station, West Lafayette, Ind. References
Cited
Bareay, S. J. 1986. Influence of flushing agents on the movement behavior of the German cockroach. M.S. thesis, Purdue University, West Lafayette, Ind. Bennett, G. W. & E. S. Runslrom. 1984. Control of German cockroaches with amidinohydrazone bait, pp. 408-409. In Insecticide and acaricide tests, vol. 9. Entomological Society of America, College Park, Md.
Burden, G. S.
& B. J. Smittle. 1975. Blattella germanica, Periplaneta americana and Monomorium pharaonis: control with insecticidal baits in an animal
building and in insectaries. J. Med. Entomol. 12:352353. Cheng, T. H. & F. L. Campbell. 1940. Toxicity of phosphorous to cockroaches. J. Econ. Entomol. 33: 193-199. Cross, T. J. & R. G. Sehnellmann. 1989. The mechanism of toxicity of a unique pesticide (N-ethylperfluorooctane sulfonamide) and its metabolite (per-
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
At LDs,» sulfluramid was significantly more toxic when ingested than when topically applied. Despite this greater toxicity, the speed of kill for sulfluramid at LTso was significantly slower when ingested than when topically applied. At ingested doses of 285.7 /oLg/g,the LTso was nearly twice that of a 100-/oLg/gtopical application; these differences in the LTso were even greater when the ingested dose (142.9 /oLg/g)more closely approximated the topical dose (100 /oLg/g).As the ingested sulfluramid dose decreased, the LTso values increased; the same result was seen in the topical applications of 100 and 50 /oLg/gsulfluramid. Different speed of kill between the two exposure methods may result from penetration of the cuticle facilitated by acetone, which was used as the solvent in topical application. When an insect's exposure to sulfluramid is by ingestion, onset of mortality is delayed in the same way as that of hydramethylnon (Silverman & Shapas 1986). Although no direct comparisons were made with hydramethylnon in this dietary study, preliminary research (B.L.R. & G. W.B., unpublished data) has suggested (and the topical data presented here would predict) that this delay in the onset of mortality after ingestion is greater for hydramethylnon than sulfluramid. Feeding Deterrence. Mean (±SEM) time to diet discovery for control diets (2.36 ± 0.86 min) did not differ significantly (t = 0.20; df = 10; P = 0.84) from that for the sulfluramid diets (2.12 ± 0.85 min). Mean time spent at the control diets (26.76 ± 6.02 min) did not differ significantly (t = 0.48; df = 10; P = 0.64) from that for the sulfluramid diets (23.10 ± 4.64 min). Mean number of visits to the control diets (40.33 ± 2.16) did not differ significantly (t = 0.00; df = 10; P = 1.00) from that for the sulfluramid diets (40.33 ± 6.08). No evidence of feeding deterrence or an avoidance response was found in the Moving-Image-Analysis study. Lack of feeding deterrence is important for development of a toxic bait with sulfluramid because the palatability of a bait product can have a dramatic impact of its effectiveness in population suppression. Data collected with Moving-Image-Analysis are only an indicator of possible deterrence. Although the starved insect's residence time at the diet pellet is highly correlated with consumption of diet (S.}.B., unpublished data), quantification of the actual diet consumption is not possible with this method. Tests that actually measure the rate and extent of diet consumption should be conducted to confirm our findings. Our test had a no-choice design, and studies where cockroaches are offered a choice of diets might give different results. Because we examined only a single concentration of sulfluramid, the possibility for a concentration-dependent response in feeding deterrence should be considered. Sulfluramid is an effective toxicant for German cockroach control and has considerable potential for application in bait products. Its greater toxicity and faster action with respect to the successful bait
B. germanica
152
JOURNAL OF ECONOMIC
Vol. 83, no. 1
Lund, R. D. & G. W. Dennell. 1978. Evaluation of Bolt bait, pp. 176-177. In Insecticide and acaricide tests, vol. 3. Entomological Society of America, College Park, Md. Reierson, D. A., M. K. Rust., A. M. VanDyke & A. G. Appel. 1982. Control of German cockroaches with amidinohydrazone bait, p. 54. In Insecticide and acaricide tests, vo\. 8. Entomological Society of America, College Park, Md. Rust, M. K. & D. A. Reierson. 1981. Attraction and performance of insecticidal baits for German cockroach control. Int. Pest Control 23: 106-109. SAS Institute 1985. SAS user's guide: statistics. SAS Institute, Cary, N.C. Silverman, J. & T. J. Shapas. 1986. Cumulative toxicity and delayed temperature effects of hydramethylnon on German cockroaches (Orthoptera: Blattellidae). J. Econ. Entomo\. 79: 1613-1616. Vander Meer, R. K., C. S. Lofgren & D. F. Williams. 1985. Fluoroaliphatic sulfones: a new class of delayed-action insecticides for control of Solenopsis invieta (Hymenoptera: Formicidae). J. Econ. Entomo\. 78: 1I90-1I97. Received for publication 7 Apri/1989.
7 December 1988; accepted
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
£luorooctane sulfonamide) to isolated rabbit renal cortical mitochondria. Toxicologist 9: 224. DeMark. J. J. 1988. Effects of chitin synthesis inhibitors on nymphal and oothecal stages of the German cockroach, Blattella germanica (L.). M.S. thesis, Purdue University, West Lafayette, Ind. Frishman, A. 1982. Cockroaches. In A. Mallis [ed.], Handbook of pest control, 6th ed. Franzak & Foster, Cleveland, Ohio. HoIlingshaus, J. G. 1987. Inhibition of mitochondrial electron transport by hydramethylnon: a new amidinohydrazone insecticide. Pestic. Biochem. Physiol. 27: 61-70. Hoy, J. D., P. A. Globus & K. D. Norman. 1983. Electronic tracking and recording system for behavioral observations with application to toxicology and pheromone assay. J. Econ. Entomol. 76: 678-680. Koehler, P. G. & R. S. Pallerson. 1986. A comparison of insecticide susceptibility in seven nonresistant strains of the German cockroach, Blattella germanica (Dictyoptera: Blattellidae) J. Med. Entomol. 74: 678-680. Lofgren, C. S. & G. S. Burden. 1958. Tests with poison baits against cockroaches. Fla. Entomo\. 41: 103-1I0. Lovell, J. B. 1979. Amidinohydrazones-a new class of insecticides. Proc. Brit. Crop Prot. Conf. Pests Dis. 2: 575-582.
ENTOMOLOGY
of Entomology,
J.
Purdue University, West Lafayette,
Indiana 47907
Econ. Entomol. 83(1): 148-152 (1990)
The LD50of sulfluramid topically applied to 2-d-old, fifth instars of the German cockroach, Blattella germanica (L.), was estimated at 14.5 p.g/g (95% FL = 13.7-15.4 p.g/ g). Sulfluramid was significantly more toxic than topically applied hydramethylnon (LD50 = 29.2 [19.0-46.5] p.g/g). Sulfluramid had delayed toxicity but caused mortality significantly faster than hydramethylnon after topical application. The oral LD50 against newly eclosed, fifth instars was estimated to be 4.1 (3.9-4.4) p.g/g; this toxicity was significantly greater than when sulfluramid was topically applied. Mortality caused by sulfluramid occurred significantly more slowly in the dietary exposures than in the topical applications. Sulfluramid at 1,000 ppm in diets was not a feeding deterrent to nymphal B. germanica. ABSTRACT
Insecta, Blattella germanica, sulfluramid, delayed-action
TOXIC FOOD BAITShave been a successful management tool for the control of several insect species, including red imported fire ant, Solenopsis invicta Buren, and Pharaoh ant, Monomorium pharaonis (L.). This treatment strategy has many advantages related to minimizing environmental contamination. Use of bait formulations typically results in less chemical use. Toxicants can be placed in more discrete areas than is possible with conventional spray treatments. If the bait base is most attractive to the target pest species, some species specificity can be achieved so that risks to nontarget organisms are reduced. For these reasons, use of toxic baits may be compatible with environmentally sound integrated pest management programs. Use of toxic baiting in the control of cockroaches has a long and varied history (Frishman 1982). Toxic baits containing phosphorous, boric acid, and other compounds were most effective against Periplaneta spp. and other large domiciliary cockroaches (Cheng & Campbell 1940, Lofgren & Burden 1958), but the more prevalent German cockroach, Blattella germanica (L.), was not successfully controlled with these products. German cockroaches were successfully controlled with baits containing chlordecone (Kepone) (Burden & Smittle 1975) for a short period of time before cancellation of their registrations by the Environmental Protection Agency during the late 1970s. Success and failure have been reported with 0.5% chlorpyrifos baits that are commonly available to consumers (Lund & Bennett 1978, Rust & Reierson 1981), but a high density of bait placements (>40 in two- or three-bedroom apartments) are required for effective population reduction. A major advance in control of the German cockroach and other cockroach species with toxic baits was the discovery of hydramethylnon (Lovell 1979). 0022-0493/90/0148-0152$02.00/0
toxicity
This compound is representative of a class of insecticides (amidinohydrazones) that inhibit mitochondrial electron transport (Hollingshaus 1987) and cause delayed mortality by disruption of respiratory energy production. The efficacy of hydramethylnon baits for cockroach control has been well documented (e.g., Bennett & Runstrom 1984, Reierson et al. 1982). The success of products containing hydramethylnon (Combat and Maxforce Roach Control System, American Cyanamid, Princeton, N.J.) has stimulated research on the strategy of controlling cockroaches with toxic baits. Sulfluramid (N-ethyl perfluorooctane sulfonamide) is a potential bait toxicant that belongs to a new class of delayed-action insecticides, the fluoroaliphatic sulfonamides (Vander Meer et al. 1985). Cross & Schnellmann (1989) showed that sulfluramid is an uncoupler of oxidative phosphorylation. In the research reported here, we compared the toxicity of sulfluramid to hydramethylnon in topical applications and evaluated its activity as a stomach poison in dietary feeding studies. The possibility of feeding deterrence associated with its presence in a food source also was examined.
Materials and Methods Blattella germanica used in this research were from a Johnson Wax strain, nonresistant to conventional insecticides (Koehler & Patterson 1986), that were maintained throughout these studies under a photoperiod of 12:12 (L:D) at 28 ± 1°e. Test insects were nymphs (fifth instar) that were obtained by establishing large groups of late fourth instars with water and harborage but no food. Thereafter, individuals found within these groups' that had molted to the fifth instar were easily dis-
© 1990 Entomological Society of America
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
KEY WORDS
February
1990
REID ET AL.: TOXICITY
OF SULFLURAMID
149
Six replicates with 10 newly ec10sed fifth instars were conducted for each of eight diet concentrations (7.8, 15.6, 31.3, 62.5, 125, 250, 500, and 1,000 ppm). Insects were established with toxic diets within 24 h of their molt to the fifth instar and were forced to consume one diet pellet before they were provided with untreated food; this typically took 2-3 d. Estimation of an oral LDso is based on the assumption that each cockroach consumed the same amount of diet (10 mg per insect) and adjusting for the weight of a 2-d-old fifth instar (approximately 35 mg). Results of the conversion of diet concentrations to oral doses were 2.2, 4.5, 8.9, 17.9,35.7,71.4,142.9, and 285.7 ~g/g. Mortality was recorded daily for 5 d after introduction of the toxic diets and once more when all surviving insects had reached adulthood (approximately 14 d). The oral LDso value for sulfluramid was estimated by regression analysis of the probit mortality to the adult stage versus loglO of dose. The LTso's for 1,000 and 500 ppm sulfluramid diets were estimated from the regression of the cumulative daily probit mortality versus loglo of time (d). SAS software (SAS Institute 1985) was used for both estimation procedures. L Tor LDso's with 95% FL that did not overlap were considered significantly different. Feeding Deterrence. The possibility of feeding avoidance resulting from the presence of sulfluramid in the only food available to the test insects was examined with a computerized Moving-Image-Analyzer modified by Barcay (1986) from the Spider Tracking Program described by Hoy et a!. (1983). This system monitors, records, and analyzes the movement behavior of individual insects within a Plexiglas observation arena (30.5 cm diameter). A IOO-mg diet pellet, prepared as described above, was glued in the center of the arena with Elmer's Glue-All (Borden, Columbus). The image analysis programming defined an area immediately surrounding this diet; interactions of a test insect with the diet pellet were monitored. A moistened cotton wick was situated to provide a water source near the edge of the arena. This wick also offered a preferred site of harborage for the test insects, which would otherwise frequent the diet pellet to fulfill their thigmotactic habits (S.J.B., unpublished data). Thigmotactic orientation to the diet pellet would be an undesirable artifact for a method designed to compare feeding responses of the insects to varying diets. Newly ec10sed fifth instars were allowed to develop with food and water for 48 h, after which they were denied food for 24 h. This starving regime allowed a rigorous (although highly artificial) evaluation of possible feeding deterrence from the sulfluramid incorporated into diets. At the conc1usion of this starving regime, the insects were liberated into the observation arena for analysis of their behavioral interactions with the diet pellet. All studies were conducted under infrared illumination to simulate scotophase conditions.
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
tinguishable from their cohorts on a daily basis, and we were certain that they had molted within the previous 24 h. The absence of food ensured that these fifth instars had not yet fed, which was an important consideration in synchronous staging of the various ages used. In all experiments, test insects were housed in disposable plastic Petri dishes (100 by 25 mm) provided with harborage, water, and food. Topical Applications. Technical grade formulations of sulfluramid (98.0%; Lipha Chemicals, Milwaukee) and hydramethylnon (95.6%; American Cyanamid, Princeton, N.J.) were diluted in acetone and applied topically in 1-~1 droplets to the intercoxal regions of the meso- and meta thoracic regions of 2-d-old, fifth instars (x ± SEM = 34.8 ± 4.1 mg, n = 40). Solutions were prepared at six rates (3.1, 6.3, 12.5, 25, 50, and 100 ~g/g body weight) for each compound; an additional series was conducted for sulfluramid at six rates (8.2, 10.3, 12.8, 16, 20, and 25 ~g/g). Each treatment was administered to a total of 60 nymphs, which were grouped (10 insects per Petri dish) for observational purposes and supplied with food, water, and harborage. Mortality was recorded daily for 7 d and again when all surviving insects had reached adulthood (approximately 12 d after treatment). LDso's for sulfluramid and hydramethylnon were estimated by regression analysis of the probit mortality to the adult stage versus loglo of dose. The speed of action (LTso) for the 100- and 50-~g/g doses of each compound was estimated by regression of the cumulative daily probit mortality versus loglo of time (d). SAS software (SAS Institute 1985) was used for both estimation pr.ocedures. The criterion of nonoverlapping 95% FL was used to estimate significant differences. Dietary Studies. In studies of dietary activity, we did not compare hydramethylnon and sulfluramid. In preliminary rate determination studies, we observed a disparity in diet consumption: 1-2 d longer were required for insects to consume 100 mg of hydramethylnon diet (100 and 1,000 ppm) than insects feeding on sulfluramid diet. These observations suggested that differential feeding (hence, toxicant exposure) would invalidate a comparison of effects of hydramethylnon and sulfluramid consumed in diet. We evaluated dietary activity of sulfluramid with procedures developed by DeMark (1988). Experimental diets were prepared by finely grinding Wayne rodent blox (Continental Grain Company, Chicago), then reconstituting this media (5 g) with an appropriate acetone solution (3 ml) of sulfluramid and water (6 ml). The resulting mixture was thoroughly mixed, pressed into Plexiglas molds, and dried for 48 h within an evacuation hood to yield pelletized diets (x ± SEM = 100 ± 2 mg). All diets were stored (5°C) in glass Petri dishes lined with filter paper and containing cotton balls as a moisture absorbent.
TO NYMPHAL B. germanica
150
JOURNAL OF ECONOMIC
la: sulfluramid
ENTOMOLOGY
Vol. 83, no. 1
The LDso (95% FL) for sulfluramid was 14.5 (13.7-15.4) p.g/g. The regression had a slope (±SE) 100 of 5.86 ± 0.17 (n = 361 insects). Sulfluramid was - ...• slope was 5.99 ± 0.17 (n = 240 observations). At .•.. lU 25 100-p.g/g doses, sulfluramid caused mortality significantly more quickly than topically applied hydramethylnon (LTso = 3.23 [2.89-3.60] d). The slope ....• o for the regression estimating the speed of kill for a 100-/.Lg/g dose of hydramethylnon was 5.07 ± Ib: hydramethylnon 0.20 (n = 300 observations). The LT50 (95% FL) for a 50-/.Lg/g dose of sulfluramid was 1.88 (1.68100 2.12) d. The slope was 4.27 ± 0.23 (n = 300 observations). At 50-p.g/g doses, sulfluramid caused mortality significantly more quickly than topically .5 75 •..o applied hydramethylnon (LT:so= 6.89 [5.78-8.52] IS d). The slope for 50 p.g/g of hydramethylnon was 2.39 ± 0.42 (n = 300 observations). ~ 50 ClI Comparisons of the topical LDsoand LT:soshowed ;> ...• .•.. that sulfluramid was twice as toxic as hydramethyllU 25 non when applied topically to 2-d-old fifth instars of B. germanica and produced mortality in less ::l ....• than half the time required for hydramethylnon . o The L Tsoat 100 p.g/g for each compound indicated 1 2 3 4 5 6 7 adults that sulfluramid kills significantly faster than hydays after treatment dramethylnon. Differences between compounds at Fig. I. Cumulative percentage of mortality in 2-d- the LT50 were even greater at 50 p.g/ g, but the 50old, fifth-instar German cockroaches following topical /.Lg/ g rate of hydramethylnon failed to achieve 100% applications of one of six doses of either sulfluramid (a) mortality (Fig. 1b). The greater toxicity and faster or hydramethylnon (b) in 1 ILlof acetone. action of sulfluramid indicate a potential for improvements in cockroach bait products. Cockroach Data from 3-h trials with the Moving-Imagebait products containing hydra methyl non, alAnalyzer were recorded for one of two diet types: though highly effective control measures, can take from 2 to 4 wk after application before significant acetone blank controls or 1,000 ppm sulfluramid. Experiments with each type of diet were replicated reductions in infestations are detected (Bennett & Runstrom 1984, Reierson et al. 1982). with six insects. The time (min) to diet discovery, the time spent at the diet (interpreted as time of Dietary Studies. Results for cumulative mortality over time for sulfluramid in diet, like those in consumption), and number of visits to the diet were evaluated to test for feeding deterrence. Mean val- the topical applications (Fig. 1), indicated that ues were analyzed by two-tailed t tests (P = 0.05; mortality induced by sulfluramid continued to acSAS Institute 1985). cumulate for several days following exposure (Fig. 2). This trend was most evident at diet concentrations of 62.5 ppm (17.9 p.g/g) and 31.3 ppm (8.9 Results and Discussion /.Lg/g). At these concentrations, mortality after 5 d Topical Applications. Although the mortality was 10 and 0%, respectively, yet had risen to 100 and 95% when surviving insects reached caused by both compounds accumulated over time, mortality induced by sulfluramid occurred more adulthood. At 7.8 ppm (2.2 p.g/g), sulfluramid was not toxic. quickly (Fig. 1). At 100 p.g/g, all insects treated with sulfluramid died by 3 d, while hydramethylThe oral LD:so(95% FL) of sulfluramid fed to non-treated insects did not die until after 7 d. At test insects (n = 328) was 4.14 (3.90-4.40) p.g/g. 50 and 25 p.g/g, mortality caused by hydramethylThe slope of the regression was 5.85 ± 0.17. The non reached thresholds (53.3 and 38.0%, respecLTso (95% FL) for the 1,000-ppm diet (285.7 p.g/ tively) at 6 d, whereas all insects treated with sul- g) was 2.14 (1.94-2.35) d. The probit regression fluramid died by 5 d. Data from the 8.2-25 p.g/g had a slope of 6.62 ± 0.15 (n = 240). The L Tso topical doses of sulfluramid (plots not shown) in- (95% FL) for diet containing 500 ppm (142.9 p.g/ dicated that mortality continued to occur beyond g) was 3.27 (2.99-3.58) d. The probit regression had a slope of 7.71 ± 0.13 (n = 240). 8 d. dose (I!gl g)
3
'a §
'ae
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
:E
February 1990
REID ET AL.: TOXICITY OF SULFLURAMID TO NYMPHAL
100
dietary cone. (ppm)
~ ;;:
--2 o
~'"
75
Ei
~ 50 ell
...•> 1U 25 '3
Ei
e
151
1000.0 500.0 250.0 125.0 62.5 31.3 15.6 7.8
0
1 2 3 4 5 adults days of 5th stage Fig. 2. Cumulative percentage of mortality in newly eclosed fifth-instar German cockroaches following consumption of 100 mg of diet containing one of eight concentrations of sulfluramid. toxicant hydramethylnon suggests that highly effective baits for the control of German cockroaches and, presumably, other cockroach species can be developed. In addition, our tests did not indicate feeding avoidance by nymphal German cockroaches to sulfluramid, which was present in the only food available; thus, feeding deterrence should not be an impediment to the development of toxic bait with sulfluramid. Delayed mortality associated with sulfluramid exposure should be especially important in the control of social insects (Vander Meer et al. 1985), in which trophallaxis from exposed individuals can spread toxicants throughout colonies. Acknowledgment We thank J. Neal and J. Owens for their critical review of early drafts of this manuscript and A. Las and A. Nethery for their technical supJXlrt.We acknowledge the partial financial support of this research by Lipha Chemical Co. This article is journal paper 11,857, Purdue University Agricultural Experiment Station, West Lafayette, Ind. References
Cited
Bareay, S. J. 1986. Influence of flushing agents on the movement behavior of the German cockroach. M.S. thesis, Purdue University, West Lafayette, Ind. Bennett, G. W. & E. S. Runslrom. 1984. Control of German cockroaches with amidinohydrazone bait, pp. 408-409. In Insecticide and acaricide tests, vol. 9. Entomological Society of America, College Park, Md.
Burden, G. S.
& B. J. Smittle. 1975. Blattella germanica, Periplaneta americana and Monomorium pharaonis: control with insecticidal baits in an animal
building and in insectaries. J. Med. Entomol. 12:352353. Cheng, T. H. & F. L. Campbell. 1940. Toxicity of phosphorous to cockroaches. J. Econ. Entomol. 33: 193-199. Cross, T. J. & R. G. Sehnellmann. 1989. The mechanism of toxicity of a unique pesticide (N-ethylperfluorooctane sulfonamide) and its metabolite (per-
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
At LDs,» sulfluramid was significantly more toxic when ingested than when topically applied. Despite this greater toxicity, the speed of kill for sulfluramid at LTso was significantly slower when ingested than when topically applied. At ingested doses of 285.7 /oLg/g,the LTso was nearly twice that of a 100-/oLg/gtopical application; these differences in the LTso were even greater when the ingested dose (142.9 /oLg/g)more closely approximated the topical dose (100 /oLg/g).As the ingested sulfluramid dose decreased, the LTso values increased; the same result was seen in the topical applications of 100 and 50 /oLg/gsulfluramid. Different speed of kill between the two exposure methods may result from penetration of the cuticle facilitated by acetone, which was used as the solvent in topical application. When an insect's exposure to sulfluramid is by ingestion, onset of mortality is delayed in the same way as that of hydramethylnon (Silverman & Shapas 1986). Although no direct comparisons were made with hydramethylnon in this dietary study, preliminary research (B.L.R. & G. W.B., unpublished data) has suggested (and the topical data presented here would predict) that this delay in the onset of mortality after ingestion is greater for hydramethylnon than sulfluramid. Feeding Deterrence. Mean (±SEM) time to diet discovery for control diets (2.36 ± 0.86 min) did not differ significantly (t = 0.20; df = 10; P = 0.84) from that for the sulfluramid diets (2.12 ± 0.85 min). Mean time spent at the control diets (26.76 ± 6.02 min) did not differ significantly (t = 0.48; df = 10; P = 0.64) from that for the sulfluramid diets (23.10 ± 4.64 min). Mean number of visits to the control diets (40.33 ± 2.16) did not differ significantly (t = 0.00; df = 10; P = 1.00) from that for the sulfluramid diets (40.33 ± 6.08). No evidence of feeding deterrence or an avoidance response was found in the Moving-Image-Analysis study. Lack of feeding deterrence is important for development of a toxic bait with sulfluramid because the palatability of a bait product can have a dramatic impact of its effectiveness in population suppression. Data collected with Moving-Image-Analysis are only an indicator of possible deterrence. Although the starved insect's residence time at the diet pellet is highly correlated with consumption of diet (S.}.B., unpublished data), quantification of the actual diet consumption is not possible with this method. Tests that actually measure the rate and extent of diet consumption should be conducted to confirm our findings. Our test had a no-choice design, and studies where cockroaches are offered a choice of diets might give different results. Because we examined only a single concentration of sulfluramid, the possibility for a concentration-dependent response in feeding deterrence should be considered. Sulfluramid is an effective toxicant for German cockroach control and has considerable potential for application in bait products. Its greater toxicity and faster action with respect to the successful bait
B. germanica
152
JOURNAL OF ECONOMIC
Vol. 83, no. 1
Lund, R. D. & G. W. Dennell. 1978. Evaluation of Bolt bait, pp. 176-177. In Insecticide and acaricide tests, vol. 3. Entomological Society of America, College Park, Md. Reierson, D. A., M. K. Rust., A. M. VanDyke & A. G. Appel. 1982. Control of German cockroaches with amidinohydrazone bait, p. 54. In Insecticide and acaricide tests, vo\. 8. Entomological Society of America, College Park, Md. Rust, M. K. & D. A. Reierson. 1981. Attraction and performance of insecticidal baits for German cockroach control. Int. Pest Control 23: 106-109. SAS Institute 1985. SAS user's guide: statistics. SAS Institute, Cary, N.C. Silverman, J. & T. J. Shapas. 1986. Cumulative toxicity and delayed temperature effects of hydramethylnon on German cockroaches (Orthoptera: Blattellidae). J. Econ. Entomo\. 79: 1613-1616. Vander Meer, R. K., C. S. Lofgren & D. F. Williams. 1985. Fluoroaliphatic sulfones: a new class of delayed-action insecticides for control of Solenopsis invieta (Hymenoptera: Formicidae). J. Econ. Entomo\. 78: 1I90-1I97. Received for publication 7 Apri/1989.
7 December 1988; accepted
Downloaded from http://jee.oxfordjournals.org/ by guest on June 9, 2016
£luorooctane sulfonamide) to isolated rabbit renal cortical mitochondria. Toxicologist 9: 224. DeMark. J. J. 1988. Effects of chitin synthesis inhibitors on nymphal and oothecal stages of the German cockroach, Blattella germanica (L.). M.S. thesis, Purdue University, West Lafayette, Ind. Frishman, A. 1982. Cockroaches. In A. Mallis [ed.], Handbook of pest control, 6th ed. Franzak & Foster, Cleveland, Ohio. HoIlingshaus, J. G. 1987. Inhibition of mitochondrial electron transport by hydramethylnon: a new amidinohydrazone insecticide. Pestic. Biochem. Physiol. 27: 61-70. Hoy, J. D., P. A. Globus & K. D. Norman. 1983. Electronic tracking and recording system for behavioral observations with application to toxicology and pheromone assay. J. Econ. Entomol. 76: 678-680. Koehler, P. G. & R. S. Pallerson. 1986. A comparison of insecticide susceptibility in seven nonresistant strains of the German cockroach, Blattella germanica (Dictyoptera: Blattellidae) J. Med. Entomol. 74: 678-680. Lofgren, C. S. & G. S. Burden. 1958. Tests with poison baits against cockroaches. Fla. Entomo\. 41: 103-1I0. Lovell, J. B. 1979. Amidinohydrazones-a new class of insecticides. Proc. Brit. Crop Prot. Conf. Pests Dis. 2: 575-582.
ENTOMOLOGY
