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Toxicity of Abamectin to Cockroaches
(Dictyoptera: Blattellidae, Blattidae)
University of Florida, Gainesville, Florida 32611 Abamectin was fed to German cockroaches, Blattella germanica choice tests. LT005and LC,oS were estimated by probit analysis. The L T005for the German ranged from 4.4 to 1.7 d for males, from 9.0 to 2.4 d for females, and from 4.4 to 1.6 d for nymphs for bait concentrations were 0.0110 and 0.0040% from males, 0.0240 and 0.0090% for females, and 0.0200 and 0.0080% for nymphs at 3 and 6 d, respectively.
bait were 3.4, 3.4, 2.4, 7.5, 2.9, and 4.5 d for Periplaneta (Serville), P. brunnea Burmeister, P. australasiae (F.), Blatta orientalis L., and species, time to death for the larger species was longer than for the German cockroach.
abamectin bait, all died within 5 d of exposure to abamectin bait. Abamectin bait consumptionwas not significantly control being achieved by treating harborages INSECTICIDALBAITShave become one of the most 1984, Miller et al. 1986, Rousch & Wright and yellowjackets (Chang 1988). Strong & Brown (1987) reviewed the mode of action of avermectins and their effect on target and nontarget species of Abamectin cockroach bait (Avert, Whitmire Re- ents used in baits can include compounds like hy- search Laboratories, St. Louis, Mo.) is a slow acting toxicant for control of German cockroaches, Blat- contact activity but are very active as stomach poi- sons (Rust 1986). Because baits can be placed in containers, insecticides that stain (e.g., hydrameth- control of the German cockroach (Ballard & Gold ylnon has a yellow color) can be applied indoors 1983, Wright & Dupree 1985). Rates of 76.5 ppm (1985) also found that low concentrations ermectin caused failure of leg muscles of American mectin BIb) is effective as a stomach poison against cockroach, Periplaneta americana (L.), to respond (Glancey et al. 1982, Baker et al. 1985), lice (Barth The objective of our study was to evaluate the & Preston 1985), clothes moths (Bry 1989), gypsy moth (Deecher et al. 1987), flies (Langley & Roe a stomach poison and causes delayed toxicity, tox-icity at various concentrations Thisarticlereportsthe resultsof researchonly.Mentionof a proprietaryproductdoesnotconstitutean endorsementor a rec- Speed of kill for a 0.0550% bait was determined I Currentaddress:Departmentof Entomology, 'Insects AffectingMan and AnimalsResearchLaboratory, suppress populations of German cockroaches were finely ground laboratory rodent chow, were placed in each glass utility jar (4.25 liter). Nylon screen germanica; Oriental cockroaches, Blatta orientalis (6.6 threads per cm) was placed on top of the pow- L.; brown banded cockroaches, Supella longipalpa dered abamectin bait and rodent chow to prevent (Serville); American cockroaches, P. americana; spillage. Water and harborage were provided as Australian cockroaches, P. australasiae (F.); brown described earlier. Preference tests were conducted in a room held at 50% RH and 25°C with a pho- lightly anesthetized with CO. and removed from Before cockroaches were released, all experi- colonies maintained at the USDA-ARS Insects Af- mental jars were placed in the laboratory for 48 h fecting Man and Animals Laboratory, Gainesville, to allow the moisture content of the baits and ro- Fla. "Orlando normal" German cockroaches were dent chow to equilibrate with the laboratory en- used in our study. This strain is susceptible to in- vironment. Twenty male German cockroaches were secticides (Koehler & Patterson 1986). Adults that then placed in each jar (lightly greased with a 2:3 had eclosed 3 d before testing and fourth- and fifth- stage nymphs were used. Males of the other species To check moisture changes in the baits, control jars were removed from laboratory colonies and were with bait and rodent chow were set up without cockroaches. To check cockroach mortality, other Whitmire Research Laboratories (St. Louis, Mo.).
with laboratory rodent chow for food.
Seven concentrations of baits ranging from 0.0025 to 0.1000% (wt/wt) were formulated on a standard laboratory rodent chow, and the number of dead bait base. Laboratory rat chow (Purina, St. Louis, Mo.) was finely ground and used as a control diet.
cockroaches were released and daily for 7 dafter After the initial dose studies with German cock- release. Five jars for the treatment, three humidity roaches, a 0.0550% (wt/wt) bait was used for all control jars, and three untreated control jars were used. Daily consumption of food and bait by the Mortality Tests. Thirty German cockroaches (10 cockroaches was corrected using the following for- male, 10 female, and 10 late-stage nymphs) were placed in glass utility jars (4.25 liter) that were lightly greased with a 2:3 (petrolatum/mineral film to prevent escape. A souffle cup containing where CC is the corrected consumption, WI is g of bait was placed in each jar. Water was weight on day 1, W. is weight on day 2, HCI is provided with a cotton-stoppered, water-filled plas- the average weights appropriate hUliJliditychecks tic vial (20 ml; 5.5 by 2.5 cm inner diameter); (3 reps) on previous day, and HC. is the average harborage was a rolled corrugated cardboard strip weights humidity checks on current day. Adjusted (6 by 15 cm). Cloth covers were placed over each food and bait consumption were analyzed by t tests German cockroaches were exposed to seven con- Arena Tests. The inside walls of 11 aluminum arenas (120 by 120 by 30 em, three per treatment) were greased lightly with a 2:3 (petrolatum/min- control (finely ground laboratory rat chow). Three eral oil) film to prevent cockroach escape. Four jars were set up for each treatment.
cardboard harborages (4.5 by 8.5 cm inner diam- were nonchoice and done at 50% RH and 25°C eter; Fonda, Union, N.J.) with holes (2 cm inner with a photoperiod of 12:12 (L:D). Numbers of diameter) cut in the side were placed midway along dead cockroaches were recorded for each jar at 1, the edge of each arena. German cockroaches (50 2, 3, 6, 8, 10, 12, and 14 d of treatment.
males, 50 females, and 280 nymphs) were placed The arenas were treated with 1.65% hydrameth- were placed in glass utility jars (4.25 liter) that were ylnon bait trays (Combat, American Cyanamid, Clifton, N.J.), abamectin bait stations (20-30 g of cockroaches were recorded for each jar at 1, 2, 3, 0.0550% [AI] abamectin) placed in a cardboard dish (2 by 8.5 cm inner diameter; Fonda), or 5 g of Data were analyzed by probit analysis (Finney abamectin bait dusted into each cockroach har- 1971) to estimate LCw values for each day of treat- borage. Dishes that contained the abamectin or the ment and LTso values for each concentration bait. Significant differences in LT50 and LC50 values each other and an equal distance from a centrally were determined by failure of 95% confidence in- placed chicken waterer (1 liter) in each arena.
Dishes that contained laboratory rat chow were placed in a similar manner, but at a 90° orientation to the dishes containing the treated bait. Control 0.0550% abamectin bait and the other containing arenas just received laboratory rodent chow. Are- LCso values (%) of German cockroaches fed fed abamectin at various bait concentrations Abamectin is a slow-acting toxicant that provides higher doses killing cockroaches faster. The speed of action for males (L Tso = 1.68 d) is slower than faster than that of sulfluramid (2.14 d at 1,000 ppm; Reid et al. 1990) and boric acid (5.06-7.63 d; Appel 1990). Both Reid et al. (1990) and Milio et al. (1986) non provide delayed mortality of cockroaches thatis dose-related.
licated three and two times, respectively.
than 6 d (Table 2). The LCsoS of abamectin males, females, and nymphs of the German cock- were generally significantly higher for females and 0.05) (SAS Institute 1988). This procedure was used 2.8, and 4.5 d, respectively (Table 3). These valueswere significantly man cockroach. Differences in bait preferences and The L TsoSfor males, females, and nymphs of the body size of these other species may account for bait (Table 1). Generally, LTsoSdecreased with in-creasing 0.0500%. No significant decrease in LTsoSwas found bait was used in additional studies. At 0.0500%, the males, females, and nymphs, respectively. Cochran high mortality at 10 d, and survivors failed to re- produce. The faster mortality times reported in ourstudy are probably attributable Data were analyzed by probit analysis (Finney (> 10 times) of abamectin bait used.
abamectin bails and laboratory rat chow by male German cockroaches in choice group means in the same column followed by the same letter are not significantly different (P = 0.05; Student's t test used to suppress populations of peridomestic cock- important in bait performance for slow-acting oral roaches, even though the time required to kill the toxicants. Over a 7-d period, male cockroach (groups larger cockroaches was> 16 d (Milio et al. 1986).
of 20) consumption of abamectin bait (7.16 mg) was not significantly less than consumption of rat er species of cockroaches and is a potentially useful chow (9.61 mg). The total consumption (16.77 mg) product for suppression of peridomestic cockroach- of food in utility jars containing abamectin was less than consumption (110.59 mg) in the control jars Preference tests of German cockroaches for the over the same period. Reduced consumption in the abamectin bait compared with laboratory rat chow treated groups was probably attributable to toxicity resulted in 100% mortality by the fifth day (Table of abamectin. Similarly, Cochran (1985) reported 4). There was no control mortality. These mortality reduced consumption of baits by female German results compare favorably with mortality obtained cockroaches at bait concentrations >0.3 ppm; but using formulated baits that contain hydramethyl- he attributed the reduced consumption to toxicity non and sulfluramid with this strain of cockroach rather than unpalatability or repellency.
Arena tests with 0.0500% abamectin and 1.65% unpublished data). The LT50 of abamectin bait in choice tests was 2.85 d (n = 100; 95% confidence tality of German cockroaches after 1-3 d (Table interval, 2.722-2.981; slope ± SE, 9.122 ± 0.084).
5). Abamectin placed in bait dishes resulted in sig- This LToowas significantly greater than the LT50 nificantly lower mortality after 9d than abamectin of a similar concentration of bait fed in non choice placed in the harborage with the cockroaches. Aba- tests (1.68 d), but was not significantly different mectin provided faster mortality than the hydra- from the L T50 of a bait that was half the concen- methylnon standard from 1 to 3 d of treatment.
tration (2.68 d for 0.0250% bait). This result would After 5 d, the abamectin treatment placed in the be expected if the bait was approximately the pal- harborage and the hyramethylnon bait stations re- atability of rat chow (rat chow is not highly pal- sulted in significantly higher mortality than the abamectin placed in the bait station or the controls.
After 9 d, abamectin placed in the harborage pro- affected (Reierson & Rust 1984) if palatability is vided 75% mortality of German cockroaches, hy- reduced. Therefore, relative palatability with re- spect to dietary alternatives is likely to be extremely mectin placed in the bait station provided 31% Percent mortality of cockroaches in arena tests treated with 0.0550% Means within a row followed by the same letter are not significantly different (P = 0.05; Tukey's Studentized range test [SAS Institute larvae and eggs. J. Econ. Entomo!. 80: 1284-1287.
Glancey, B. M., C. S. Lofgren & D. F. Williams.
possible control agent for the tsetse fly, Glossina mor- sitans. Entomo!. Exp. App!. 36: 137-143.
Miller, J. A., D. D. Oehler & A. J. Siebenaler.
horn flies and stable flies. J. Econ. Entomo!. 79: 1564- We thank Troy Whitfield, Eurypides Mena, and Susan Ard for their technical assistance. We also thank Whit- cockroach suppression with hydramethylnon support of this project. This is Florida Agricultural B1attellidae) control. J. Econ. Entomo!.
T. C., S. E. Van Vorhis Key & L. K. Gaston.
386. In G. W. Bennett J. M. Owens [eds.l Advances contro!. Bull. Entomo!. Res. 77: 357-389.
10 degrees, 15.5 degrees, and 27 degrees C for control mectin B on the leg muscles and the nervous system trans (L.) (Diptera: Muscidae). J. Kans. Entomo!. Soc.
of the American cockroach. Pestic. Biochem. Physio!.

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