Operational Evaluation Of Vectomax® WSP (Bacillus thuringiensis Subsp. israelensis + Bacillus sphaericus) Against Larval Culex pipiens in Septic Tanks Author(s): Huseyin Cetin, Emre Oz, Atila Yanikoglu, and James E. Cilek Source: Journal of the American Mosquito Control Association, 31(2):193-195. Published By: The American Mosquito Control Association DOI: http://dx.doi.org/10.2987/15-6480R URL: http://www.bioone.org/doi/full/10.2987/15-6480R
BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/ terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder.
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
Journal of the American Mosquito Control Association, 31(2):193–195, 2015 Copyright E 2015 by The American Mosquito Control Association, Inc.
OPERATIONAL NOTE OPERATIONAL EVALUATION OF VECTOMAXH WSP (BACILLUS THURINGIENSIS SUBSP. ISRAELENSIS + BACILLUS SPHAERICUS) AGAINST LARVAL CULEX PIPIENS IN SEPTIC TANKS1 HUSEYIN CETIN,2 EMRE OZ,2 ATILA YANIKOGLU2
AND
JAMES E. CILEK3
ABSTRACT. The residual effectiveness of VectoMaxH WSP (a water-soluble pouch formulation containing a combination of Bacillus thuringiensis subsp. israelensis strain AM65-52 and B. sphaericus strain ABTS 1743) when applied to septic tanks against 3rd- and 4th-stage larvae of Culex pipiens L. was evaluated in this study. This formulation was evaluated at operational application rates of 1 pouch (10 g) and 2 pouches (20 g) per septic tank. Both application rates resulted in .96% control of larvae for 24 days. Operationally, VectoMax WSP has proven to be a useful tool for the nonchemical control of Culex species in septic tank environments. KEY WORDS Bacillus thuringiensis subsp. israelensis, B. sphaericus, Culex pipiens, septic tanks, watersoluble pouch formulation
Open septic tanks are a common source for mosquito production in Antalya, Turkey. Specifically, Culex pipiens L. develops in these highly enriched organic habitats and by its prolific nature is the most abundant species and important possible disease vector in Turkey (Cetin et al. 2005, 2007; Ocal et al. 2014). Different types of insecticide formulations, such as insect growth regulators, are commonly used to control mosquitoes in these tanks. Currently, biweekly applications of chitin synthesis inhibitors or juvenile hormone analogs are routinely applied to open septic tanks by vector control teams without assessing the presence or absence of mosquito larvae. Because larval control measures are applied indiscriminately in Antalya, Turkey with a narrow range of active ingredients, the risk of developing resistance, we believe, may be substantial. An additional class of products currently available for operational use by mosquito control agencies is the microbial pesticide products of Bacillus thuringiensis subsp. israelensis (Bti) and B. sphaericus (Bs). Like many biological products used in larval control, effectiveness is often based on mosquito species and habitat. For example, in a study by 1 Mention of a trademark, vendor, or proprietary product does not constitute a guarantee or warranty of the product by the US Navy and does not imply its approval to the exclusion of other products that may also be suitable. The views expressed in this manuscript are those of the authors and do not reflect the official policy or position of the Navy and Marine Corps Public Health Center, Navy Bureau of Medicine and Surgery, Department of Defense, or the US Government. 2 Biology Department, Faculty of Science, Akdeniz University, 07058 Antalya, Turkey. 3 The Navy Entomology Center of Excellence, PO Box 43, Naval Air Station, Jacksonville, FL 32212.
Pantuwatana (1989), Bti activity against larval Cx. quinquefasciatus Say in organic-rich water was short lived (90–100% control through 18 days); whereas Bs provided nearly 100% control for 60 days in similar habitats. Silapanuntakul et al. (1983), reported that Bti-treated tap water provided complete (100%) reduction of larvae of Cx. quinquefasciatus for 1 wk posttreatment, declining to 50% at 10 wk posttreatment. This same study evaluated Bs-treated tap and polluted water against larval Cx. quinquefasciatus and achieved a constant 90% mortality level in both types of water quality that lasted for 9 months in tap water and 6 months in polluted water. Unfortunately, field resistance to Bs has been reported in this species after 2–3 years of application (Mulla et al. 2003). But tank mixtures of Bti and Bs have been reported in the literature as very effective in controlling mosquito larvae in septic tank habitats and could provide an operational strategy to prevent and/or reduce the buildup of Bs resistance development in Culex species (Zahiri et al. 2002, Cetin et al. 2007). Indeed, Wirth et al. (2004) reported that the combination of Bti and Bs toxins synergistically enhanced toxicity against Cx. quinquefasciatus larvae. Currently, there is a commercially available mixture that combines Bti (strain AM65-52) and Bs 2362 (strain ABTS 1743) into single microparticles by a proprietary binding process marketed under the trade name VectoMaxH WSP (Valent Biosciences Corporation). This product is packaged as a combined granule concentrate enclosed in a water-soluble pouch (WSP). The WSP formulation was developed by the manufacturer at the request of customers for direct application to catch basins and other contained water sources for control of mosquito larvae (Peter DuChant, Valent Biosciences Corporation, personal communication).
193
Means within a column followed by the same letter are not significantly different according to Tukey’s multiple comparison test (P 5 0.05). 1
52 45 38 31
0.82 6 0.54 a 1.62 6 0.58 a 2.55 6 0.75 a 2.97 6 0.50 a 3.95 6 1.52 a (96.22) (80.40) (49.06) (38.86) (27.39) 2.12 6 1.19 ab 7.37 6 5.73 a 4.05 6 2.07 a 5.47 6 2.54 a 6.72 6 2.92 a (96.30) (67.04) (70.10) (57.02) (55.46) 32.3 6 23.00 b 12.30 6 1.30 a 7.45 6 0.85 a 7.00 6 1.00 a 8.30 6 1.00 a
24 17 10
0.08 6 0.08 a 0.82 6 0.49 a 0.55 6 0.37 a (99.99) (97.43) (96.74) 62.45 6 22.5 a 0a 0a 0.40 6 0.40 a (100) (100) (99.10) 34.45 6 12.15 a 26.45 6 21.15 b 47.65 6 37.65 b 25.15 6 18.15 b 23.16 6 10.0 a
3
VOL. 31, NO. 2
One pouch (10 g) Two pouches (20 g) Control (untreated)
0 (pretreatment)
where C1 5 pretreatment population density in control habitat, C2 5 posttreatment population density in control habitat, T1 5 pretreatment population density in treatment habitat, and T2 5 posttreatment population density in treatment habitat. Mean abundance data for 3rd and 4th instars were combined and analyzed with a 2-way analysis of variance with treatment and sample day, and their interaction, used in the model (Zar 1999). Differences in larval abundance between treated and untreated septic tanks for each collection day were determined with the use of Tukey’s multiple comparison test (a 5 0.05) with
Treatment
%Reduction~100{½ðC1=T1Þ|ðT2=C2Þ|100,
Mean no. larvae/dip per sample day
To determine if this formulation could be of benefit to mosquito control programs in Turkey, we operationally evaluated the residual effectiveness of VectoMax WSP in septic tank habitats against Cx. pipiens larvae. Field studies were conducted in the Yurtpınar region, Antalya, Turkey during July and August 2009. In this region, monthly average temperature can range from 20uC to 36uC with relative humidity ranging from 60% to 80%. VectoMax WSP (2.7% active ingredient [AI] B. thuringiensis subsp. israelensis serotype H-14, strain AM65-52 plus 4.5% AI B. sphaericus serotype H5a5b, 2362 strain ABTS 1743, Valent Biosciences Corporation, Libertyville, IL) was used in all tests. Most households in Yurtpınar utilize septic tanks for disposal of domestic waste. Four septic tanks per VectoMax treatment were selected for our study. The study tanks contained abundant larval populations of Cx. pipiens based on pretreatment 500-ml dipper samples. Tanks varied in size and depth, but were assumed to average about 10 m2 in surface area, as previously described by Cetin et al. (2007). Two similar untreated septic tanks served as controls. Septic tanks were treated at an application rate of 1 pouch (10 g) per tank and 2 pouches (20 g) per tank. Therefore, the total number of septic tanks in the study was 10. A minimum of 3 dipper samples were taken at various points along the surface of each septic tank and the number of larvae per instar per dip recorded. On the day of treatment, larvae in all septic tanks were sampled before application of VectoMax. Once treated, septic tanks were sampled on day 3 and then every 7 days through 52 days posttreatment. All larval samples were counted in the field and returned to their respective septic tanks. Because the vast majority of samples contained 3rd and 4th instars these larval stages were pooled and percent larval reduction was calculated for each treated septic tank, at each sample date, using the formula of Mulla et al. (1971):
Mean number (6SE) of Culex pipiens larvae (3rd and 4th instars combined) collected from septic tanks before and after treatment with VectoMaxH WSP at 2 application rates. Percent larval reduction for each VectoMax treatment is shown in bold parenthesis.1
JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION
Table 1.
194
JUNE 2015
OPERATIONAL NOTE
Intel Visual Fortran Compiler XE software (2013, Intel Corporation, Santa Clara, CA). Treatment, sample day, and their interaction were significantly different (P . 0.0001) where dates influenced treatments and variation among treatments was different among sample days. Culex pipiens larval abundance in septic tanks treated at either application rate with VectoMax WSP was significantly reduced for 24 days compared with untreated controls (Table 1). Complete larval control (100%) was achieved with 2 pouches per septic tank for 10 days posttreatment, whereas 1 pouch provided slightly lower control. However, both application rates provided adequate (.96%) reduction of larvae for 24 days, even though reduction with 2 pouches was not significantly different than controls on that sample period because of high variability of larval abundance in samples on that date. During our study, mean abundance of small instars (1st and 2nd) were similarly reduced in these treated tanks, but numbers were too low to provide meaningful results for analyses (data not shown). At 31 days, the 1-pouch application rate provided .80% control of 3rd- and 4th-stage larvae, whereas the 2-pouch application had dropped considerably below this level. Although a certain level of larval reduction in treatment tanks appeared to continue for the remainder of the 52-day study, these differences were not significant compared with larval abundance in control tanks (Table 1). A study conducted by Anderson et al. (2011) found that VectoMax WSP–treated catch basins in the City of Stratford, CT could provide significant control of Aedes japonicus (Theobald) and Culex 3rd and 4th instars for 2 wk as compared with untreated basins. Our results from septic tanks provided slightly greater control than the above study. Obviously, differences in water volume, habitat quality, and target species can affect the residual efficacy of any larvicidal product. However, we do note that our results are well within the range of retreatment recommendations (1–4 wk) for polluted water habitats on the VectoMax WSP label. We found that VectoMax WSP proved to be very efficacious for operational long-term residual control of larval Cx. pipiens in highly polluted open-water habitats in Turkey. The authors are thankful to Akdeniz University, Scientific Research Projects Committee Unit, Antalya, for financial support. We would like to thank Heiko Kotter (Valent BioSciences
195
Corporation) for his useful suggestions. Also, appreciation is extended to Alec Richardson, Navy Entomology Center of Excellence, for his assistance with statistical analyses. REFERENCES CITED Anderson JF, Ferrandino FJ, Dingman DW, Main AJ, Andreadis TG, Becnel JJ. 2011. Control of mosquitoes in catch basins in Connecticut with Bacillus thuringiensis israelensis, Bacillus sphaericus, and spinosad. J Am Mosq Control Assoc 27:45–53. Cetin H, DeChant P, Yanikoglu A. 2007. Field trials with tank mixtures of Bacillus thuringiensis subsp. israelensis and Bacillus sphaericus formulations against Culex pipiens larvae in septic tanks in Antalya, Turkey. J Am Mosq Control Assoc 23:161–165. Cetin H, Yanikoglu A, Cilek JE. 2005. Evaluation of the naturally-derived insecticide spinosad against Culex pipiens L. (Diptera: Culicidae) larvae in septic tank water in Antalya, Turkey. J Vector Ecol 30:151–154. Mulla MS, Norland RL, Fanara DM, Darwazeh HA, McKean DW. 1971. Control of chironomid midges in recreational lakes. J Econ Entomol 64:300–307. Mulla MS, Thavara U, Tawatsin A, Chomposrf J, Su TY. 2003. Emergence of resistance and resistance management in field populations of tropical Culex quinquefasciatus to the microbial control agent Bacillus sphaericus. J Am Mosq Control Assoc 19:39–46. Ocal M, Orsten S, Inkaya AC, Yetim E, Acar NP, Alp S, Erisoz Kasap O, Gunay F, Arsava EM, Alten B, Ozkul A, Us D, Niedrig M, Ergunay K. 2014. Ongoing activity of Toscana virus Genotype A and West Nile virus lineage 1 strains in Turkey: a clinical and field survey. Zoonoses Public Health 61:480–491. Pantuwatana S. 1989. The prospect of Bacillus thuringiensis var. israelensis and Bacillus sphaericus in mosquito control in Thailand. Israel J Entomol 23:51–57. Silapanuntakul S, Pantuwatana S, Bhumiratana A, Charoensiri K. 1983. The comparative persistence of toxicity of Bacillus sphaericus strain 1593 and Bacillus thuringiensis serotype H-14 against mosquito larvae in different kinds of environments. J Invertebr Pathol 42:387–392. Wirth MC, Jiaqnnion JA, Federici BA, Walton WE. 2004. Synergy between toxins of Bacillus thuringiensis subsp. israelensis and Bacillus sphaericus. J Med Entomol 41:935–941. Zahiri NS, Mulla MS, Su T. 2002. Strategies for management of resistance in mosquitoes to the microbial control agent Bacillus sphaericus. J Med Entomol 39:513–530. Zar JH. 1999. Biostatistical analysis. 4th ed. Upper Saddle River, NJ: Prentice Hall: 663 pp.
BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/ terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder.
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.
Journal of the American Mosquito Control Association, 31(2):193–195, 2015 Copyright E 2015 by The American Mosquito Control Association, Inc.
OPERATIONAL NOTE OPERATIONAL EVALUATION OF VECTOMAXH WSP (BACILLUS THURINGIENSIS SUBSP. ISRAELENSIS + BACILLUS SPHAERICUS) AGAINST LARVAL CULEX PIPIENS IN SEPTIC TANKS1 HUSEYIN CETIN,2 EMRE OZ,2 ATILA YANIKOGLU2
AND
JAMES E. CILEK3
ABSTRACT. The residual effectiveness of VectoMaxH WSP (a water-soluble pouch formulation containing a combination of Bacillus thuringiensis subsp. israelensis strain AM65-52 and B. sphaericus strain ABTS 1743) when applied to septic tanks against 3rd- and 4th-stage larvae of Culex pipiens L. was evaluated in this study. This formulation was evaluated at operational application rates of 1 pouch (10 g) and 2 pouches (20 g) per septic tank. Both application rates resulted in .96% control of larvae for 24 days. Operationally, VectoMax WSP has proven to be a useful tool for the nonchemical control of Culex species in septic tank environments. KEY WORDS Bacillus thuringiensis subsp. israelensis, B. sphaericus, Culex pipiens, septic tanks, watersoluble pouch formulation
Open septic tanks are a common source for mosquito production in Antalya, Turkey. Specifically, Culex pipiens L. develops in these highly enriched organic habitats and by its prolific nature is the most abundant species and important possible disease vector in Turkey (Cetin et al. 2005, 2007; Ocal et al. 2014). Different types of insecticide formulations, such as insect growth regulators, are commonly used to control mosquitoes in these tanks. Currently, biweekly applications of chitin synthesis inhibitors or juvenile hormone analogs are routinely applied to open septic tanks by vector control teams without assessing the presence or absence of mosquito larvae. Because larval control measures are applied indiscriminately in Antalya, Turkey with a narrow range of active ingredients, the risk of developing resistance, we believe, may be substantial. An additional class of products currently available for operational use by mosquito control agencies is the microbial pesticide products of Bacillus thuringiensis subsp. israelensis (Bti) and B. sphaericus (Bs). Like many biological products used in larval control, effectiveness is often based on mosquito species and habitat. For example, in a study by 1 Mention of a trademark, vendor, or proprietary product does not constitute a guarantee or warranty of the product by the US Navy and does not imply its approval to the exclusion of other products that may also be suitable. The views expressed in this manuscript are those of the authors and do not reflect the official policy or position of the Navy and Marine Corps Public Health Center, Navy Bureau of Medicine and Surgery, Department of Defense, or the US Government. 2 Biology Department, Faculty of Science, Akdeniz University, 07058 Antalya, Turkey. 3 The Navy Entomology Center of Excellence, PO Box 43, Naval Air Station, Jacksonville, FL 32212.
Pantuwatana (1989), Bti activity against larval Cx. quinquefasciatus Say in organic-rich water was short lived (90–100% control through 18 days); whereas Bs provided nearly 100% control for 60 days in similar habitats. Silapanuntakul et al. (1983), reported that Bti-treated tap water provided complete (100%) reduction of larvae of Cx. quinquefasciatus for 1 wk posttreatment, declining to 50% at 10 wk posttreatment. This same study evaluated Bs-treated tap and polluted water against larval Cx. quinquefasciatus and achieved a constant 90% mortality level in both types of water quality that lasted for 9 months in tap water and 6 months in polluted water. Unfortunately, field resistance to Bs has been reported in this species after 2–3 years of application (Mulla et al. 2003). But tank mixtures of Bti and Bs have been reported in the literature as very effective in controlling mosquito larvae in septic tank habitats and could provide an operational strategy to prevent and/or reduce the buildup of Bs resistance development in Culex species (Zahiri et al. 2002, Cetin et al. 2007). Indeed, Wirth et al. (2004) reported that the combination of Bti and Bs toxins synergistically enhanced toxicity against Cx. quinquefasciatus larvae. Currently, there is a commercially available mixture that combines Bti (strain AM65-52) and Bs 2362 (strain ABTS 1743) into single microparticles by a proprietary binding process marketed under the trade name VectoMaxH WSP (Valent Biosciences Corporation). This product is packaged as a combined granule concentrate enclosed in a water-soluble pouch (WSP). The WSP formulation was developed by the manufacturer at the request of customers for direct application to catch basins and other contained water sources for control of mosquito larvae (Peter DuChant, Valent Biosciences Corporation, personal communication).
193
Means within a column followed by the same letter are not significantly different according to Tukey’s multiple comparison test (P 5 0.05). 1
52 45 38 31
0.82 6 0.54 a 1.62 6 0.58 a 2.55 6 0.75 a 2.97 6 0.50 a 3.95 6 1.52 a (96.22) (80.40) (49.06) (38.86) (27.39) 2.12 6 1.19 ab 7.37 6 5.73 a 4.05 6 2.07 a 5.47 6 2.54 a 6.72 6 2.92 a (96.30) (67.04) (70.10) (57.02) (55.46) 32.3 6 23.00 b 12.30 6 1.30 a 7.45 6 0.85 a 7.00 6 1.00 a 8.30 6 1.00 a
24 17 10
0.08 6 0.08 a 0.82 6 0.49 a 0.55 6 0.37 a (99.99) (97.43) (96.74) 62.45 6 22.5 a 0a 0a 0.40 6 0.40 a (100) (100) (99.10) 34.45 6 12.15 a 26.45 6 21.15 b 47.65 6 37.65 b 25.15 6 18.15 b 23.16 6 10.0 a
3
VOL. 31, NO. 2
One pouch (10 g) Two pouches (20 g) Control (untreated)
0 (pretreatment)
where C1 5 pretreatment population density in control habitat, C2 5 posttreatment population density in control habitat, T1 5 pretreatment population density in treatment habitat, and T2 5 posttreatment population density in treatment habitat. Mean abundance data for 3rd and 4th instars were combined and analyzed with a 2-way analysis of variance with treatment and sample day, and their interaction, used in the model (Zar 1999). Differences in larval abundance between treated and untreated septic tanks for each collection day were determined with the use of Tukey’s multiple comparison test (a 5 0.05) with
Treatment
%Reduction~100{½ðC1=T1Þ|ðT2=C2Þ|100,
Mean no. larvae/dip per sample day
To determine if this formulation could be of benefit to mosquito control programs in Turkey, we operationally evaluated the residual effectiveness of VectoMax WSP in septic tank habitats against Cx. pipiens larvae. Field studies were conducted in the Yurtpınar region, Antalya, Turkey during July and August 2009. In this region, monthly average temperature can range from 20uC to 36uC with relative humidity ranging from 60% to 80%. VectoMax WSP (2.7% active ingredient [AI] B. thuringiensis subsp. israelensis serotype H-14, strain AM65-52 plus 4.5% AI B. sphaericus serotype H5a5b, 2362 strain ABTS 1743, Valent Biosciences Corporation, Libertyville, IL) was used in all tests. Most households in Yurtpınar utilize septic tanks for disposal of domestic waste. Four septic tanks per VectoMax treatment were selected for our study. The study tanks contained abundant larval populations of Cx. pipiens based on pretreatment 500-ml dipper samples. Tanks varied in size and depth, but were assumed to average about 10 m2 in surface area, as previously described by Cetin et al. (2007). Two similar untreated septic tanks served as controls. Septic tanks were treated at an application rate of 1 pouch (10 g) per tank and 2 pouches (20 g) per tank. Therefore, the total number of septic tanks in the study was 10. A minimum of 3 dipper samples were taken at various points along the surface of each septic tank and the number of larvae per instar per dip recorded. On the day of treatment, larvae in all septic tanks were sampled before application of VectoMax. Once treated, septic tanks were sampled on day 3 and then every 7 days through 52 days posttreatment. All larval samples were counted in the field and returned to their respective septic tanks. Because the vast majority of samples contained 3rd and 4th instars these larval stages were pooled and percent larval reduction was calculated for each treated septic tank, at each sample date, using the formula of Mulla et al. (1971):
Mean number (6SE) of Culex pipiens larvae (3rd and 4th instars combined) collected from septic tanks before and after treatment with VectoMaxH WSP at 2 application rates. Percent larval reduction for each VectoMax treatment is shown in bold parenthesis.1
JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION
Table 1.
194
JUNE 2015
OPERATIONAL NOTE
Intel Visual Fortran Compiler XE software (2013, Intel Corporation, Santa Clara, CA). Treatment, sample day, and their interaction were significantly different (P . 0.0001) where dates influenced treatments and variation among treatments was different among sample days. Culex pipiens larval abundance in septic tanks treated at either application rate with VectoMax WSP was significantly reduced for 24 days compared with untreated controls (Table 1). Complete larval control (100%) was achieved with 2 pouches per septic tank for 10 days posttreatment, whereas 1 pouch provided slightly lower control. However, both application rates provided adequate (.96%) reduction of larvae for 24 days, even though reduction with 2 pouches was not significantly different than controls on that sample period because of high variability of larval abundance in samples on that date. During our study, mean abundance of small instars (1st and 2nd) were similarly reduced in these treated tanks, but numbers were too low to provide meaningful results for analyses (data not shown). At 31 days, the 1-pouch application rate provided .80% control of 3rd- and 4th-stage larvae, whereas the 2-pouch application had dropped considerably below this level. Although a certain level of larval reduction in treatment tanks appeared to continue for the remainder of the 52-day study, these differences were not significant compared with larval abundance in control tanks (Table 1). A study conducted by Anderson et al. (2011) found that VectoMax WSP–treated catch basins in the City of Stratford, CT could provide significant control of Aedes japonicus (Theobald) and Culex 3rd and 4th instars for 2 wk as compared with untreated basins. Our results from septic tanks provided slightly greater control than the above study. Obviously, differences in water volume, habitat quality, and target species can affect the residual efficacy of any larvicidal product. However, we do note that our results are well within the range of retreatment recommendations (1–4 wk) for polluted water habitats on the VectoMax WSP label. We found that VectoMax WSP proved to be very efficacious for operational long-term residual control of larval Cx. pipiens in highly polluted open-water habitats in Turkey. The authors are thankful to Akdeniz University, Scientific Research Projects Committee Unit, Antalya, for financial support. We would like to thank Heiko Kotter (Valent BioSciences
195
Corporation) for his useful suggestions. Also, appreciation is extended to Alec Richardson, Navy Entomology Center of Excellence, for his assistance with statistical analyses. REFERENCES CITED Anderson JF, Ferrandino FJ, Dingman DW, Main AJ, Andreadis TG, Becnel JJ. 2011. Control of mosquitoes in catch basins in Connecticut with Bacillus thuringiensis israelensis, Bacillus sphaericus, and spinosad. J Am Mosq Control Assoc 27:45–53. Cetin H, DeChant P, Yanikoglu A. 2007. Field trials with tank mixtures of Bacillus thuringiensis subsp. israelensis and Bacillus sphaericus formulations against Culex pipiens larvae in septic tanks in Antalya, Turkey. J Am Mosq Control Assoc 23:161–165. Cetin H, Yanikoglu A, Cilek JE. 2005. Evaluation of the naturally-derived insecticide spinosad against Culex pipiens L. (Diptera: Culicidae) larvae in septic tank water in Antalya, Turkey. J Vector Ecol 30:151–154. Mulla MS, Norland RL, Fanara DM, Darwazeh HA, McKean DW. 1971. Control of chironomid midges in recreational lakes. J Econ Entomol 64:300–307. Mulla MS, Thavara U, Tawatsin A, Chomposrf J, Su TY. 2003. Emergence of resistance and resistance management in field populations of tropical Culex quinquefasciatus to the microbial control agent Bacillus sphaericus. J Am Mosq Control Assoc 19:39–46. Ocal M, Orsten S, Inkaya AC, Yetim E, Acar NP, Alp S, Erisoz Kasap O, Gunay F, Arsava EM, Alten B, Ozkul A, Us D, Niedrig M, Ergunay K. 2014. Ongoing activity of Toscana virus Genotype A and West Nile virus lineage 1 strains in Turkey: a clinical and field survey. Zoonoses Public Health 61:480–491. Pantuwatana S. 1989. The prospect of Bacillus thuringiensis var. israelensis and Bacillus sphaericus in mosquito control in Thailand. Israel J Entomol 23:51–57. Silapanuntakul S, Pantuwatana S, Bhumiratana A, Charoensiri K. 1983. The comparative persistence of toxicity of Bacillus sphaericus strain 1593 and Bacillus thuringiensis serotype H-14 against mosquito larvae in different kinds of environments. J Invertebr Pathol 42:387–392. Wirth MC, Jiaqnnion JA, Federici BA, Walton WE. 2004. Synergy between toxins of Bacillus thuringiensis subsp. israelensis and Bacillus sphaericus. J Med Entomol 41:935–941. Zahiri NS, Mulla MS, Su T. 2002. Strategies for management of resistance in mosquitoes to the microbial control agent Bacillus sphaericus. J Med Entomol 39:513–530. Zar JH. 1999. Biostatistical analysis. 4th ed. Upper Saddle River, NJ: Prentice Hall: 663 pp.
