Progress 10/01/05 to 09/30/10
Outputs
OUTPUTS: Experiments were conducted and analyzed. Four graduate students and nine undergraduate students participated in research related activities. Research findings were presented and disseminated at the annual meetings of the Entomological Society of America and the Mosquito and Vector Control Association of California. A publication on current practices in wetland management for mosquito control was developed with wetlands scientists and mosquito control practitioners for the Society of Wetland Scientists newsletter. Our research findings were included in an invited chapter in a book on aquatic invasive species. Other outreach activities included participation as an invited member of the Southern California Vector Control Environmental Taskforce which promoted dialog and exchange of information among natural resource management agencies, permitting agencies such as the Army Corps of Engineers, vector control and public health agencies; participation in the Southern California Native Freshwater Fauna Working Group which is a consortium of representatives from natural resources agencies, academia, consulting firms, Cooperative Extension and other agencies that meets regularly to discuss ongoing activities related to conservation, assessment, public policy and regulations and other topics related to riparian wetlands and other aquatic habitats of southern California; participation as a technical advisor for the Vector Habitat Remediation Program in San Diego County; and as liaison between the University of California and the Mosquito and Vector Control Association of California. Significant outputs were carried out through webinars, face-to-face outreach interactions with interested parties, presentations (oral and posters) at scientific meetings, peer-reviewed scientific publications, and both web-based and paper-based publications for the general public. PARTICIPANTS: PI: Dr. William Walton, Dept. of Entomology, Univ. California, Riverside, CA Staff: Dr. Margaret Wirth, SRA IV, Dept. of Entomology, Univ. California, Riverside, CA; David Popko, Lab. Asst., Dept. Entomology, Univ. California, Riverside, CA; Anita Gordillo, Lab. Asst., Dept. Entomology, Univ. California, Riverside, CA; Peter Brabant, Lab. Asst., Dept. Entomology, Univ. California, Riverside, CA; Jennifer Thieme, Lab. Asst., Dept. Entomology, Univ. California, Riverside, CA Graduate Students: Donald Beasley, Dagne Duguma, Jennifer Henke, Adena Why, Mary Sorensen, Peter Jensen, Dept. of Entomology, Univ. of California, Riverside, CA Undergraduate Assistants: Henrique Chan, Christina Handayan, Kevin Mai, Ngoc Nguyen, Justin Richardson, Rex Tse, Andrew Nguyen, Tristan Hallum, Samantha Wong; Cooperators: Dr. Brian Federici, Dept. of Entomology, Univ. California, Riverside, CA; Jeffrey Johnson, SRA IV, Dept. of Entomology, Univ. California, Riverside, CA; Bonnie Nash, Orange County Water District, Fountain Valley, CA; Richard Zembal, Orange County Water District, Fountain Valley, CA. Training opportunities were provided for four graduate students and nine undergraduate assistants. Dr. Brian Federici and Mr. Johnson collaborated with Drs. Walton and Wirth on studies of bacterial larvicides and provided the Bacillus strains used in the selection experiments focused on the evolution of resistance in mosquitoes. Richard Zembal and Bonnie Nash collaborated on studies of the arroyo chub as a replacement for mosquitofish in integrated mosquito management programs in sensitive wetlands and watersheds of southern California. The California Dept. of Fish and Game and the Freshwater Native Fauna Working Group (a consortium of southern California scientists) are contacts on the project. TARGET AUDIENCES: The target audience includes wetlands practitioners, natural resource managers, vector control and public health personnel and other individuals involved in water reclamation activities that utilize constructed treatment wetland to improve water quality. Efforts included training of graduate and undergraduate students through the delivery of science-base knowledge by classroom and laboratory instruction, and outreach activities with Dr. Sabrina Drill. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Outcomes included the generation of new knowledge that was included in six new publications for a total of 41 publications for this project. Topics of new knowledge included improved management techniques for mosquito populations associated with man-made and natural wetlands; an improvement of environmentally friendly methods for controlling vectors of disease-causing pathogens of humans, companion animals and wildlife; and a greater understanding of the evolutionary mechanisms underlying resistance in insects. Information was provided to assist the general public for the prevention of production of mosquitoes and adoption of safe preventative measures against biting insects. Changes of conditions that resulted from this project included reduced use of chemical pesticides, improved water quality of wastewaters and stormwaters, improved methods for reducing the production of pest and vector insects during water reclamation, and improvement in the quality of life for citizens of California.
Publications
- Walton, W. E., J. A. Henke and A. M. Why. 2011. Mosquitofish (GAMBUSIA AFFINIS and GAMBUSIA HOLBROOKI). Chap. 23. In: R. Francis (ed.), A Handbook of Global Freshwater Invasive Species. Earthscan. London, U.K. In press.
- Berg, J. A., M. G. Felton, J. L. Gecy, A. D. Laderman, C. R. Mayhew, J. L. Mengler, W. H. Meredith, N. R. Read, J. R. Rey, C. Roberts, G. E. Sakolsky-Hoopes, W. E. Walton, and R. J. Wolfe. 2010. Mosquito Control and Wetlands. Wetland Science and Practice 27(2): 24-34.
- Gordillo, A. R., and W. E. Walton. 2010. Effects of Larval Diet on Life History Traits of CULEX Mosquitoes. Proc. Papers Mosq. Vector Control Assoc. Calif. 78: 16-18.
- Wirth, M. C. 2010. Mosquito Resistance to Bacterial Larvicidal Toxins. The Open Toxicology Journal (3): 110-115.
- Wirth, M. C., W. E. Walton, and B. A. Federici. 2010. Inheritance Patterns, Dominance, Stability and Allelism of Insecticide Resistance and Cross-resistance in Two Colonies of CULEX QUINQUEFASCIATUS (Diptera: Culicidae) Selected with Cry-toxins from BACILLUS THURINGIENSIS subsp. ISRAELENSIS. Journal of Medical Entomology 47: 814-822.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Experiments were conducted and analyzed. Four graduate students were trained and seven undergraduate students participated in research related activities. Research findings were presented and disseminated at the annual meetings of the Entomological Society of America and the Mosquito and Vector Control Association of California, at an invited departmental seminar at the University of California Davis, and by webinar for the American Society of Civil Engineers. A PDF of a presentation on mosquito management in constructed treatment wetlands was provided for the compilation on compact disk and for distribution to faculty, students, consultants and other interested parties. A PDF and recording of the webinar were made for distribution and for viewing by engineers, planners and other individuals interested in the topic of mosquito-related issues at constructed treatment wetlands. A publication (number 7451) on IPM of mosquitoes around the home was updated for the U.C. Division of Agriculture and Natural Resources and distributed in hard copy format and via the ANR web page. A publication on current practices in wetland management for mosquito control was developed with wetlands scientists and mosquito control practitioners for the Society of Wetland Scientists and was published on the SWS web site. Other outreach activities included participation as an invited member of the Southern California Vector Control Environmental Taskforce which promoted dialog and exchange of information among natural resource agencies, permitting agencies such as the Army Corps of Engineers, vector control and public health agencies; participation in the Southern California Native Freshwater Fauna Working Group which is a consortium of representatives from natural resources agencies, academia, consulting firms, cooperative extension and other agencies that meets regularly to discuss ongoing activities related to conservation, assessment, public policy and regulations and other topics related to riparian, wetlands and other aquatic habitats of southern California; participation as a technical advisor for the Vector Habitat Remediation Program in San Diego County; and as liaison between the University of California and the Mosquito and Vector Control Association of California. PARTICIPANTS: Dr. William Walton oversaw the project. Dr. Margaret Wirth carried out studies on resistance in mosquitoes to larvicides and assisted with other aspects of the study. Four graduate students were trained and seven undergraduate students participated in research related activities. Dr. Brian Federici and Mr. Jeffrey Johnson collaborated with Drs. Walton and Wirth on studies of bacterial larvicides. Partner organizations included the Orange County Water District, Orange County Vector Control District, Northwest Mosquito and Vector Control District, Coachella Valley Mosquito and Vector Control District and California Dept. of Fish and Game. Outreach activities were coordinated with Dr. Sabrina Drill, a member of Cooperative Extension for Los Angeles and Ventura counties and stationed at U.C. Davis. TARGET AUDIENCES: The target audience includes wetlands practitioners, natural resource managers, vector control and public health personnel and other individuals involved in water reclamation activities that utilize constructed treatment wetlands to improve water quality. Efforts included training of graduate and undergraduate students through the delivery of science-based knowledge by classroom and laboratory instruction, and outreach activities with Dr. Sabrina Drill. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Outcomes include the generation of new knowledge that was included in eight publications. Topics of new knowledge included improved management techniques for mosquito populations associated with man-made and natural wetlands; a model that predicts the extent that sampling methods underestimate mosquito production from wetlands; recognition of an important confounding factor in the interpretation of efficacy studies of biological control agents for mosquitoes; an improvement of environmentally friendly methods for controlling vectors of disease-causing pathogens of humans, companion animals and wildlife; and a greater understanding of the evolutionary mechanisms underlying resistance in insects. Information was provided to assist the general public in change of actions for the prevention of production of mosquitoes and adoption of safe preventative measures against biting insects. Changes of conditions that resulted from this project included reduced use of chemical pesticides, improved water quality of wastewaters and storm waters, improved methods for reducing the production of pest and vector insects during water reclamation, and improvement in the quality of life for citizens of California.
Publications
- Wirth, M. C., W. E. Walton and B. A. Federici. 2010. Evolution of resistance to the BACILLUS SPHAERICUS Bin toxin is phenotypically masked by combination with the mosquitocidal proteins of BACILLUS THURINGIENSIS subspecies ISRAELENSIS. Environmental Microbiology: In press.
- Walton, W. E. 2009. Effectiveness of pyramidal emergence traps for estimating production of CULEX mosquitoes (Diptera: Culicidae). Journal of the North American Benthological Society 28: 676-682.
- Walton, W. E., and B. F. Eldridge. 2009. Mosquitoes: Integrated pest management around the home. Pest Notes, Publ. No. 7451. University of California, Division of Agriculture and Natural Resources, Davis, CA. 5 pp.
- Berg, J., M. Felton, D. Fish, L. Gecy, A. Laderman, C. Mayhew, J. Mengler, W. H. Meredith, N. Read, J. Rey, C. Roberts, G. Sakolsky-Hoopes, W. E. Walton, B. Warner, and R. Wolfe. (alphabetical list) 2009. Current practices in wetland management for mosquito control. Wetland Concerns Committee. Society of Wetlands Scientists. SWS Web page. 19p.
- Henke, J. A., and W. E. Walton. 2009. Effects of vegetation on the efficacy of larval mosquito (Diptera: Culicidae) control by a native larvivorous fish. Proc. Papers Mosq. Vector Control Assoc. Calif. 77: 224-229.
- Popko, D. A., M. R. Sanford and W. E. Walton. 2009. The influence of water quality and vegetation on mosquitofish in mosquito control programs in wastewater wetlands. Proc. Papers Mosq. Vector Control Assoc. Calif. 77: 230-237.
- Walton, W. E., A. R. Van Dam and D. A. Popko. 2009. Ovipositional responses of two CULEX (Diptera: Culicidae) species to larvivorous fish. Journal of Medical Entomology 48: 1338-1343.
- Harbison, J. E., M. E. Metzger, W. E. Walton, and R. Hu. 2009. Evaluation of factors for rapid development of CULEX QUINQUEFASCIATUS in belowground stormwater treatment devices. Journal of Vector Ecology 34(2): 182-190.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Mosquito production from two bulrush species (SCHOENOPLECTUS CALIFORNICUS and SCHOENOPLECTUS MARITIMUS) with or without sprinkler treatments was evaluated in replicate wetland mesocosms. The sprinkler treatment effectively decreased egg laying by mosquitoes, reducing the abundance of mosquito egg rafts by more than two orders-of-magnitude (> 200-fold reduction) and consequently decreasing the abundance of immature mosquitoes by more than one order-of-magnitude (> 17-fold reduction). The predominant mosquitoes collected were CULEX TARSALIS and CULEX STIGMATOSOMA. The trends of mosquito abundance were similar in the two bulrush species despite different life history characteristics of the plants. On average, S. MARITIMUS was significantly more dense (50% more stems per unit area), spread faster (12% higher percent cover), and was 50 cm shorter than S. CALIFORNICUS. A natural annual die-off of S. MARITIMUS began during autumn and all of the above-substrate growth was dead by mid-winter. This material should provide an important source of organic carbon to the bacteria important for denitrification in wetlands; however, the short stature and shallow roots of S. MARITIMUS will probably limit its distribution in constructed treatment wetlands where windy conditions and comparatively deep water conditions are expected to favor the larger S. CALIFORNICUS and TYPHA SPP. Long-term selection studies of the genetic response in the mosquito CULEX QUINQUEFASCIATUS to the larvicidal toxins of BACILLUS were continued. Two colonies of C. QUINQUEFASCIATUS have been under selection pressure with recombinant microbial strains expressing either the toxins naturally found in both BACILLUS THURINGIENSIS ISRAELENSIS and BACILLUS SPHAERICUS or a combination of the binary toxin from B. SPHAERICUS, the CRY11Ba toxin from B.THURINGIENSIS JEGATHESAN, and the CYT1A toxin from B. T. ISRAELENSIS. A selection study was begun using the B.T.ISRAELENSIS-B. SPHAERICUS recombinant against the malaria vector ANOPHELES GAMBIAE to evaluate the efficacy and long-term utility of recombinant bacteria for mosquito control. Investigations of alternative microbial toxins, particularly the MTX toxins from B. SPHAERICUS, were carried out to determine the toxicity and interactions with Bin toxins from B. SPHAERICUS and with Cry toxins from B. THURINGIENSIS. Mutated toxins of B. T. ISRAELENSIS and two unusual B. SPHAERICUS proteins (CRY48Aa, CRY49Aa) were also tested against the various colonies of insecticide resistant C. QUINQUEFASCIATUS. Several synergistic interactions among the toxins were identified that may be useful for improving the activity of microbial toxins in recombinant strains of bacteria. PARTICIPANTS: PI: Dr. William Walton, Dept. of Entomology, Univ. California, Riverside, CA Staff: Dr. Margaret Wirth, SRA IV, Dept. of Entomology, Univ. California, Riverside, CA; David Popko, Lab. Asst., Dept. Entomology, Univ. California, Riverside, CA; Anita Gordillo, Lab. Asst., Dept. Entomology, Univ. California, Riverside, CA Graduate Students: Donald Beasley, Dagne Duguma, Jennifer Henke, Adena Why, Dept. of Entomology, Univ. of California, Riverside, CA Undergraduate Assistants: Peter Brabant, Jonalle Haug, Jonathan Nguyen, Bich Nguyen, Ngoc Nguyen Cooperators: Dr. Brian Federici, Dept. of Entomology, Univ. California, Riverside, CA; Jeffrey Johnson, SRA IV, Dept. of Entomology, Univ. California, Riverside, CA; Dr. Colin Berry, Cardiff School of Biosciences, Cardiff Univ., Cardiff, Wales, United Kingdom; R. G. Monnerat, Embrapa Recursos Geneticos e Biotechnologia, Parque Estacao Biologica, Brasilia, Brasil; G. W. Jones, Cardiff School of Biosciences, Cardiff Univ., Cardiff, Wales, U.K.; Z. Otieno-Ayayo, Dept. of Life Sciences, Ben-Gurion Univ. of the Negev, Be'er Sheva, Israel; Dr. Arieh Zaritsky, Dept. of Life Sciences, Ben-Gurion Univ. of the Negev, Be'er Sheva, Israel; Dr. Eitan Ben-Dov, Biotechnology Engineering, Achva Academic College, MP Shikmim, Israel; Dr. Robert Manasherob, Dept. of Genetics, Stanford Univ. Medical School, Palo Alto, CA; Dr. Vadim Khasdan, Dept. Entomology, Gilat Research Center, M.P. Negev, Israel; Dr. Rivka Cahan, Dept. of Chemical Engineering and Biotechnology, Ariel University, Ariel, Israel; Bonnie Nash, Orange County Water District, Fountain Valley, CA; Richard Zembal, Orange County Water District, Fountain Valley, CA Training opportunities were provided for four graduate students and five undergraduate assistants. Dr. Brian Federici and Mr. Johnson collaborated with Drs. Walton and Wirth on studies of bacterial larvicides and provided the Bacillus strains used in the selection experiments focused on the evolution of resistance in mosquitoes. Drs. Berry, Jones and Monerrat collaborated on the studies of the Mtx and Cry toxins investigating their potential to increase toxicity and reduce expression of insecticide resistance in mosquitoes. Drs. Zaritsky, Cahan, Ben-Dov, Manasherob, and Khasdan collaborated on studies of the efficacy and cross-resistance spectra of mosquitoes resistant to toxins in BACILLUS THURINGIENSIS ISRAELENSIS. Richard Zembal and Bonnie Nash collaborated on studies of the arroyo chub as a replacement for mosquitofish in integrated mosquito management programs in sensitive wetlands and watersheds of southern California. The California Dept. of Fish and Game and the Freshwater Native Fauna Working Group (a consortium of southern California scientists) are contacts on the project. The PI served as an invited member of a task force convened by the California Department of Public Health that developed and published recommendations for Best Management Practices for Mosquito Control on State-owned Properties TARGET AUDIENCES: The target audiences include public health agencies (California Department of Health), vector control agencies in the region, federal and state natural resource agencies, municipal governments, water districts and Regional Water Quality Control Boards. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands and natural wetlands as developmental sites. Accurate surveillance of vector abundance is required to provide information critical to decision-making for the management and prevention of vector-borne diseases. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction of large-scale wetlands systems that will be designed to conserve precious water resources, promote the biodiversity of endemic wetlands organisms, and protect the public from mosquitoes and the diseases that they cause.
Publications
- Van Dam, A. R. and W. E. Walton. 2008. The Effect of Predatory Fish Exudates on the Ovipositional Behaviour of Three Mosquito Species: CULEX QUINQUEFASCIATUS, AEDES AEGYPTI and CULEX TARSALIS. Medical and Veterinary Entomology 22: 399-404.
- Peck, G. W. and W. E. Walton. 2008. Effect of Mosquitofish (GAMBUSIA AFFINIS) and Sestonic Food Abundance on the Invertebrate Community within a Constructed Treatment Wetland. Freshwater Biology 53: 2220-2233.
- Heft, D. E. and W. E. Walton. 2008. Effects of the El Nino - Southern Oscillation (ENSO) Cycle on Mosquito Populations in Southern California. Journal of Vector Ecology 33: 17-29.
- Otieno-Ayayo, Z., A. Zaritsky, M. C. Wirth, R. Manasherob, V. Khasdan, R. Cahan, and E. Ben-Dov. 2008. Variations in Mosquito Larvicidal Activities of Toxins from BACILLUS THURINGIENSIS var. ISRAELENSIS. Environ. Microbiol. 10 (9):2191-2199.
- Jones, G. W., M. C. Wirth, R. G. Monnerat, and C. Berry. 2008. The Cry48Aa - Cry49Aa Binary Toxin from BACILLUS SPHAERICUS Exhibits Highly Restricted Target Specificity. Environ. Microbiol. 10 (9): 2418 - 2424.
- Nielsen, C., V. Kramer, D. Kwasney, D. Schnabel, M. Metzger, W. K. Reisen, W. E. Walton, et. al. 2008. Best Management Practices for Mosquito Control on California State Properties. California Department of Public Health. California Department of Public Health. 64pp.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Studies with novel insecticidal bacterial toxins focused on long-term laboratory selection studies to evaluate the risk for resistance to recombinant bacteria that were engineered to enhance their toxicity, host range, and reduce the risk for insecticide resistance by Dr. Brian Federici's laboratory. One recombinant, expressing the insecticidal toxins from both BACILLUS THURINGIENSIS ISRAELENSIS and BACILLUS SPHAERICUS, has not caused resistance in the mosquito CULEX QUINQUEFASCIATUS despite 3 years of intensive selection pressure. We have extended studies with this recombinant to include the malaria mosquito, ANOPHLELES GAMBIAE. Tests of previously unknown B. SPHAERICUS toxins (Mtx-1, Mtx-2, Cry49A) showed that Mtx toxins synergize B. SPHAERICUS and Cry11Aa from B. THURINGIENSIS ISRAELENSIS, and may prove useful for engineering novel recombinant bacterial insecticides for a reduced risk for resistance associated with certain strains of B. SPHAERICUS. We also evaluated the
mosquitocidal activity of lyophilized powders derived from recombinant ANABAENA (blue-green algae) that expresses selected toxins from B. THURINGIENSIS ISRAELENSIS. The preliminary results showed the recombinant ANABAENA was highly toxic to susceptible C. QUINQUEFASCIATUS but was poorly active toward resistant larvae. The efficacy of a native fish, the arroyo chub (GILA ORCUTTI), as a biological control agent for mosquitoes and as a replacement for the non-native mosquitofish (GAMBUSIA AFFINIS) in integrated mosquito management (IMM) programs was evaluated in 28 square meter experimental wetlands at the U.C. Riverside Aquatic and Vector Control Research Facility. Bulrush (SCHOENOPLECTUS CALIFORNICUS) was planted in nursery pots and distributed among 12 wetlands. The effects of three vegetation patch sizes (0.1, 0.4 and 0.9 square meters) on the abundance of mosquitoes and co-occurring aquatic invertebrates were investigated concurrently in wetlands containing the arroyo chub versus
wetlands lacking the arroyo chub. During the late autumn and early spring, the abundance of larval mosquitoes in ponds containing the arroyo chub were reduced by more than 2-fold as compared to ponds without fish. Relative to wetlands lacking fish, the abundance of nontarget macroinvertebrates was not affected by the presence of the arroyo chub. Samples from the spring, summer and early autumn are currently being processed to assess the abundance of mosquitoes and associated invertebrates during the peak annual periods of both mosquito and arroyo chub reproduction. Results to date indicate that G. ORCUTTI is a viable replacement for the mosquitofish in IMM programs in sensitive watersheds and wetlands in the South Coastal drainage of southern California.
PARTICIPANTS: PI: Dr. William Walton, Dept of Entomology, Univ. California, Riverside, CA Staff: Dr. Margaret Wirth, SRA IV, Dept of Entomology, Univ. California, Riverside, CA; David Popko, Lab Asst, Dept Entomology, Univ. California, Riverside, CA;Anita Gordillo, Lab Asst, Dept. Entomology, Univ. California, Riverside, CA Graduate Students: Dept of Entomology or EEOB Program, Univ of California, Riverside, CA: Donald Beasley, Anita Gordillo, Jennifer Henke, Alex Van Dam Undergraduate Assistants: Peter Brabant, Jonalle Haug, Hart Lee, Jonathan Nguyen, Ngoc Nguyen Cooperators: Dr. Brian Federici, Dept of Entomology, Univ. California, Riverside, CA Jeffrey Johnson, SRA IV, Dept of Entomology, Univ. California, Riverside, CA Dr. Colin Berry, Cardiff School of Biosciences, Cardiff Univ., Cardiff, Wales, United Kingdom Dr. Yangkun Yang, Cardiff School of Biosciences, Cardiff Univ., Cardiff, Wales, U.K. Dr. Arieh Zaritsky, Dept of Life Sciences, Ben-Gurion Univ. of the Negev, Be'er Sheva,
Israel Dr. Sammy Boussiba, Dept of Life Sciences, Ben-Gurion Univ., Be'er Sheva, Israel Dr. Eitan Ben-Dov, Biotechnology Engineering, Achva Academic College, MP Shikmim, Israel Dr. Robert Manasherob, Dept of Genetics, Stanford Univ Medical School, Palo Alto, CA Dr. Vadim Khasdan, Dept. Entomology, Gilat Research Center, M.P. Negev, Israel Dr. George Peck, Northwest Mosquito and Vector Control District, Corona, CA Bonnie Nash, Orange County Water District, Fountain Valley, CA Richard Zembal, Orange County Water District, Fountain Valley, CA Kerwin Russel, Riverside-Corona Conservation District, Riverside, CA Training opportunities were provided for four graduate students and five undergraduate assistants. Two of the students (Gordillo and Van Dam) received M.S. degrees from UCR during the reporting period. Dr. Brian Federici and Mr. Johnson collaborated with Drs. Walton and Wirth on studies of bacterial larvicides and provided the Bacillus strains used in the selection experiments
focused on the evolution of resistance in mosquitoes. Drs. Berry and Yang collaborated on the studies of the Mtx toxins investigating their potential to increase toxicity and reduce expression of insecticide resistance in mosquitoes. Drs. Zaritsky, Boussiba, Ben-Dov, Manasherob, and Khasdan collaborated on studies of the efficacy and cross-resistance spectra of mosquitoes resistant to toxins in BACILLUS THURINGIENSIS ISRAELENSIS towards recombinant strains of ESCHERICHIA COLI and ANABAENA expressing the toxin genes from B. THURINGIENSIS ISRAELENSIS. Richard Zembal and Bonnie Nash, Kerwin Russell and Dr. George Peck collaborated on studies of the arroyo chub as a replacement for mosquitofish in integrated mosquito management programs in sensitive wetlands and watersheds of southern California. The California Dept. of Fish and Game and the Freshwater Native Fauna Working Group (a consortium of southern California scientists) are contacts on the project. A sampling protocol for
evaluating the efficacy of Mosquito Best Management Practices for State-owned Wetlands was written by the PI. The Mosquito and Vector Control Association of California and the California Dept. Fish and Game reviewed the document.
TARGET AUDIENCES: The target audiences include public health agencies (California Department of Health), vector control agencies in the region, federal and state natural resource agencies, municipal governments, water districts and Regional Water Quality Control Boards.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands and natural wetlands as developmental sites. Accurate surveillance of vector abundance is required to provide information critical to decision-making for the management and prevention of vector-borne diseases. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction of large-scale wetlands systems that will be designed to conserve precious water resources, promote the biodiversity of endemic wetlands organisms, and protect the public from mosquitoes and the diseases that they cause.
Publications
- Wirth, M. C., A. Zaritsky, E. Ben-Dov, R. Manasherob, V. Khasdan, S. Boussiba, and W. E. Walton. 2007. Cross-resistance Spectra of CULEX QUINQUEFASCIATUS Resistant to Mosquitocidal Toxins of BACILLUS THURINGIENSIS toward Recombinant ESCHERICHIA COLI Expressing Genes from B. THURINGIENSIS subsp. ISRAELENSIS. Environmental Microbiology 9: 1393-1401.
- Wirth, M. C., Y. Yang, W. E. Walton, B. A. Federici, and C. Berry. 2007. Mtx Toxins Synergize BACILLUS SPHAERICUS and Cry11Aa Against Susceptible and Insecticide-Resistant CULEX QUINQUEFASCIATUS. Applied and Environmental Microbiology: 73 (19): 6066-6071.
- Walton, W. E., M. C. Wirth and P. W. Workman. 2007. Environmental Factors Influencing Survival of Threespine Stickleback GASTEROSTEUS ACULEATUS in a Multipurpose Constructed Treatment Wetland in Southern California. Journal of Vector Ecology 32: 90-105.
- Walton, W. E. 2007. Larvivorous Fish Including GAMBUSIA. In: Biorational Control of Mosquitoes. (T. Floore, ed.) American Mosquito Control Association, Bull. No. 7, Mount Laurel, NJ. Journal of the American Mosquito Control Association 23 (2) Suppl.: 184-220.
- Van Dam, A. R. and W. E. Walton. 2007. Comparison of Mosquito Control Provided by the Arroyo Chub GILA ORCUTTI and the Mosquitofish GAMBUSIA AFFINIS. Journal of the American Mosquito Control Association 23: 430-441.
- Jensen, P. D., M. A. Sorensen, W. E. Walton, and J. T. Trumble. 2007. Lethal and Sublethal Responses of an Aquatic Insect CULEX QUINQUEFASCIATUS (Diptera: Culicidae) Challenged with Individual and Joint Exposure to Dissolved Sodium Selenate and Methyl Mercury Chloride. Environmental Toxicology 22: 287-294.
- Sorensen, M. A., W. E. Walton and J. T. Trumble. 2007. Impact of the Inorganic Pollutants Perchlorate and Hexavalent Chromium on the Efficacy of BACILLUS SPHAERICUS and B. THURINGIENSIS subsp. ISRAELENSIS against CULEX QUINQUEFASCIATUS (Diptera: Culicidae). Journal of Medical Entomology 44: 811-816.
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Progress 01/01/06 to 12/31/06
Outputs
Two 6-week trials were conducted in 0.028 hectare earthen ponds to compare the efficacy of the arroyo chub, GILA ORCUTTI, to the mosquitofish, GAMBUSIA AFFINIS, as a biological control agent for mosquitoes and a possible replacement for the mosquitofish in sensitive watersheds of southern California. The mosquitofish population growth rate was 1.73 times greater than the arroyo chub population growth rate; however, greater reproduction by GAMBUSIA did not result in significantly better reduction of mosquitoes than was provided by the comparatively smaller populations of GILA. On average across a 6-week study in the spring, both larvivorous fishes reduced the abundance of 3rd and 4th instars of CULEX mosquitoes by 4- to 5-fold that observed in the control ponds that lacked fish but contained few invertebrate predators. The abundance of non-target microinvertebrates in ponds containing the mosquitofish was only 7% that in ponds containing the arroyo chub during the
summer, but did not differ significantly between the fish species treatments when zooplankton was comparatively more abundant during the spring. Even though the number of individuals produced by each fish species during 6 week in the spring was greater than for fish stocked in the summer, species-specific population growth rates in the spring study were only slightly higher than in the summer indicating that differences in the number of fish stocked contributed primarily to the differences of final population size between spring and summer studies. GILA ORCUTTI is native to the South Coastal drainages in California and should be considered as a viable alternative to GAMBUSIA AFFINIS for integrated mosquito management programs in riverine wetlands and sensitive watersheds of southern California. Two mosquitocidal toxins (Mtx) of BACILLUS SPHAERICUS were investigated for their potential to increase toxicity and reduce the expression of insecticide resistance through their interactions
with other mosquitocidal proteins. Fusion proteins of Mtx-1 or Mtx-2 and glutathione-S-transferase were induced in ESCHERICHIA COLI and the sporulated, lyophilized powders were assayed against CULEX QUINQUEFASCIATUS larvae. Both Mtx proteins showed strong activity against susceptible and resistant mosquitoes. When Mtx-1 or Mtx-2 was mixed with BACILLUS SPHAERICUS or a recombinant BACILLUS THURINGIENSIS strain expressing the toxin Cry11Aa, synergy improved activity and reduced resistance levels. Activity levels for the mixtures of Mtx toxins with BACILLUS SPHAERICUS were equal to baseline BACILLUS SPHAERICUS activity, illustrating the influence of relatively low concentrations of these toxins. Similar to Cyt toxins from BACILLUS THURINGIENSIS, Mtx toxins play important roles in toxicity and may be useful for increasing the activity of BACILLUS SPHAERICUS strains and managing resistance in mosquito populations.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands and natural wetlands as developmental sites. Accurate surveillance of vector abundance is required to provide information critical to decision-making for the management and prevention of vector-borne diseases. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction of large-scale wetlands systems that will be designed to conserve precious water resources, promote the biodiversity of endemic wetlands organisms, and protect the public from mosquitoes and the diseases that they cause.
Publications
- Peck, G. W. and W. E. Walton. 2006. The Effect of Bacterial Food Quality and Density on Growth and Whole Body Stoichiometry of CULEX QUINQUEFASCIATUS and CULEX TARSALIS (Diptera: Culicidae). Journal of Medical Entomology 43: 25-33.
- Popko, D. A., S.-K. Han, B. L. Lanoil, and W. E. Walton. 2006. A Molecular Ecological Analysis of Planktonic Bacterial Communities in Constructed Wetlands Invaded by CULEX (Diptera: Culicidae) Mosquitoes. Journal of Medical Entomology 43: 1153-1163.
- Sorensen, M. A., P. D. Jensen, W. E. Walton and J. T. Trumble. 2006. Acute and Chronic Activity of Perchlorate and Hexavalent Chromium Contamination on the Survival and Development of CULEX QUINQUEFASCIATUS Say (Diptera: Culicidae). Environmental Pollution 144: 759-764.
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Progress 01/01/05 to 12/31/05
Outputs
The relative effectiveness as biological control agents for mosquitoes of the arroyo chub (GILA ORCUTTI) and the mosquitofish (GAMBUSIA AFFINIS) was studied in 0.028 hectare mesocosms. Four adult and 35 larval arroyo chubs (mean wet weight per mesocosm: 12.53 grams) or 4 large, gravid mosquitofish among 18-25 fish (mean wet weight per mesocosm: 9.43 grams) were added to each mesocosm. Each fish species was added to three mesocosms so that the variation in larval mosquito abundance was equalized between the two fish treatments. The abundances of immature mosquitoes and two groups of nontarget organisms (microinvertebrates and macroinvertebrates) were measured using hand dippers. At the end of the experiment, fish production was measured. The arroyo chub and the mosquitofish provided similar levels of mosquito control. The abundance of late instar (3rd and 4th instars) CULEX mosquito larvae declined 20-fold by day 30 after adding the fish to the mesocosms. The diversity
of nontarget invertebrates differed between the two fish treatments: microinvertebrates (zooplankton) in mesocosms containing arroyo chubs were 3-times more abundant than in mesocosms with mosquitofish. The number of macroinvertebrates collected in dipper samples did not differ significantly between mesocosms with the arroyo chub and the mosquitofish. Fish production differed significantly between the two treatments. The mean wet weight of GILA individuals was 1.5-times greater than for individual GAMBUSIA. Total biomass of the mosquitofish (57.8 kilograms per hectare) exceeded that of the arroyo chubs (4.6 kilograms per hectare) at one month after stocking fish because many more mosquitofish were produced per mesocosm than were arroyo chubs. The arroyo chub was not adversely affected by high water temperatures that were detrimental to other native fishes. The results from this study were promising for the use of the native arroyo chub as a replacement for the non-native mosquitofish
in integrated mosquito management programs, especially for riverine wetlands in southern California. CULEX QUINQUEFASCIATUS populations were selected to recombinant strains of BACILLUS THURINGIENSIS that produced Cyt1Aa, Cry11Aa or a 1:3 mixture of these strains. After 20 generations, the resistance ratio was 1237 in the Cry11Aa-selected population, 242 in the Cyt1Aa-selected population and only 8 in population selected with the combination of the toxins. When the resistant strain selected with the combination of toxins was assayed against Cry11Aa after 48 generations, resistance was 9.3-fold. These results indicate even though resistance to Cry11Aa evolved in the presence of Cyt1Aa, the level of resistance was much lower than when Cyt1Aa was absent. Cyt1Aa is the principal factor responsible for delaying the evolution and expression of resistance to mosquitocidal Cry proteins.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands and natural wetlands as developmental sites. Accurate surveillance of vector abundance is required to provide information critical to decision-making for the management and prevention of vector-borne diseases. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction of large-scale wetlands systems that will be designed to conserve precious water resources, promote the biodiversity of endemic wetlands organisms, and protect the public from mosquitoes and the diseases that they cause.
Publications
- Wirth, M. C., H.-W. Park, W. E. Walton, and B. A. Federici. 2005. Cyt1A of BACILLUS THURINGIENSIS delays the evolution of resistance to Cry11A in the mosquito, CULEX QUINQUEFASCIATUS. Applied and Environmental Microbiology 71: 185-189.
- Park, H.-W., D. K. Bideshi, M. C. Wirth, J. J. Johnson, W. E. Walton, and B. A. Federici. 2005. Recombinant larvicidal bacteria with markedly improved efficacy against CULEX vectors of West Nile virus. American Journal of Tropical Medicine and Hygiene 72: 732-738.
- Wirth, M. C., J. A. Jiannino, B. A. Federici, and W. E. Walton. 2005. Evolution of resistance to BACILLUS SPHAERICUS or a mixture of B. SPHAERICUS + Cyt1A from BACILLUS THURINGIENSIS in the mosquito CULEX QUINQUEFASCIATUS (Diptera: Culicidae). Journal of Invertebrate Pathology 88: 154-162.
- Walton, W. E. and J. A. Jiannino. 2005. Vegetation management to stimulate denitrification increases mosquito abundance in multipurpose constructed wetlands. Journal of the American Mosquito Control Association 21: 22-27.
- Peck, G. W. and W. E. Walton. 2005. Effect of natural assemblages of larval foods on CULEX QUINQUEFASCIATUS and CULEX TARSALIS (Diptera: Culicidae) growth and whole body stoichiometry. Environmental Entomology 34: 767-774.
- Sanford, M. R., K. Chan, and W. E. Walton. 2005. Effects of inorganic nitrogen enrichment on mosquitoes (Diptera: Culicidae) and the associated aquatic community in a constructed treatment wetland. Journal of Medical Entomology 42: 766-776.
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Progress 01/01/04 to 12/31/04
Outputs
The effects of three vegetation planting regimes on mosquito production and water quality improvement were studied in replicate 0.1 hectare experimental wetlands. The mosquito production and water quality improvement associated with wetlands containing one of three types of raised planting beds supporting emergent vegetation, the bulrush SCHOENOPLECTUS CALIFORNICUS, were studied. Mosquito abundance increased in all treatments during the spring. Mosquito production per unit area of vegetated water surface did not differ significantly among the treatments during the spring. In early summer, wetlands supporting comparatively dense stands of vegetation produced numbers of CULEX greater than did wetlands supporting comparatively sparse vegetation. Unplanned fluctuations in water level significantly reduced mosquito abundance in some of the wetland cells by forcing immature stages of mosquitoes into open water where they were readily consumed by predatory insects. All
mosquito populations were eliminated from the wetlands by mid-July because the presence of the WEST NILE VIRUS in adult mosquitoes necessitated treatment of all standing water with mosquitocides. Wetlands containing emergent vegetation growing in isolated stands reduced 5-day biochemical oxygen demand significantly more than did wetlands containing vegetation in 1.5-meter wide or 5-meter wide strips. Concentrations of nitrite nitrogen, nitrate nitrogen, ammonium nitrogen, organic nitrogen and total suspended solids did not differ significantly among the three vegetation planting regimes. A strategy for delaying the phenotypic expression of resistance was tested by exposing CULEX QUINQUEFASCIATUS larvae to BACILLUS SPHAERICUS alone or in combination with the Cyt1Aa toxin from BACILLUS THURINGIENSIS ISRAELENSIS. The mosquito strain sensitive to BACILLUS SPHAERICUS evolved more than 1000-fold resistance when selected with either BACILLUS SPHAERICUS or a 3:1 mixture of BACILLUS SPHAERICUS
and CYT1Aa. A strain that underwent parallel long-term selection with a combination of BACILLUS SPHAERICUS and CYT1Aa exhibited only low resistance. Although selection with BACILLUS SPHAERICUS and CYT1Aa did not prevent evolution of resistance in the mosquitoes, the component toxins acted synergistically and will provide longer lasting and more effective mosquito control than will BACILLUS SPHAERICUS alone.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands and natural wetlands as developmental sites. Accurate surveillance of vector abundance is required to provide information critical to decision-making for the management and prevention of vector-borne diseases. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction of large-scale wetlands systems that will be designed to conserve precious water resources, promote the biodiversity of endemic wetlands organisms, and protect the public from mosquitoes and the diseases that they cause.
Publications
- Jiannino, J. A. and W. E. Walton. 2004. Evaluation of vegetation management strategies for controlling mosquitoes in a southern California constructed wetland. Journal of the American Mosquito Control Association 20: 18-26.
- Sanford, M. R. and W. E. Walton. 2004. A new collection record for URANOTAENIA ANHYDOR in Southern California. Journal of the American Mosquito Control Association 20: 85-86.
- Wirth, M. C., A. Delecluse, and W. E. Walton. 2004. Laboratory selection for resistance to BACILLUS THURINGIENSIS subsp. JEGATHESAN or a component toxin, Cry 11B, in CULEX QUINQUEFASCIATUS Say (Diptera: Culicidae). Journal of Medical Entomology 41: 435-441.
- Keiper, J. B., M. Stanczak, and W. E. Walton. 2003. Adult Chloropidae (Diptera) associated with constructed treatment wetlands modified by three vegetation management techniques. Entomological News 114: 205-210.
- Wirth, M. C., J. A. Jiannino, B. A. Federici, and W. E. Walton. 2004. Synergy between toxins from BACILLUS THURINGIENSIS subsp. ISRAELENSIS and BACILLUS SPHAERICUS. Journal of Medical Entomology 41: 935-941.
- Wirth, M.C., W. E. Walton, R. Manasherob, V. Khasdan, E. Ben-Dov, S. Boussiba, and A. Zaritsky. 2004. Larvicidal activitites of transgenic ESCHERICHIA COLI against susceptible and BACILLUS THURINGIENSIS ISRAELENSIS-resistant strains of CULEX QUINQUEFASCIATUS. Symposium on the "Ecological Impact of Genetically Modified Organisms." IOBC/WPRS Bulletin 27: 171-176.
- Knight, R. L., W. E. Walton, G. F. OMeara, W. K. Reisen, and R. Wass. 2004. Strategies for effective mosquito control in constructed treatment wetlands. Ecological Engineering 21 (Dec. 2003): 211-232.
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Progress 01/01/03 to 12/31/03
Outputs
The effects of three vegetation planting regimes on mosquito production and water quality improvement were studied in replicate 0.1 hectare experimental wetlands. Three types of raised planting beds were constructed and emergent vegetation, the bulrush SCHOENOPLECTUS CALIFORNICUS, was transplanted onto the planting beds during the summer. Mosquito abundance declined appreciably by five weeks after flooding and water quality did not differ significantly among the three treatments; these results are not surprising because the vegetation was still sparse and did not yet differ among the planting regimes. Potential differences in mosquito production and water quality performance among the three treatments are expected during the second year of the study after the bulrush has filled the planting beds. Bacterial diversity in the experimental wetlands was quantified using density-gradient gel electrophoresis (DGGE). Patterns of bacterial diversity changed similarly across
time regardless of vegetation planting regime and thirteen bacteria types (bands) were associated with high mosquito abundance. The DNA within the bands is currently being sequenced for later testing of these bacteria types/groups as putative attractants to egg laying mosquitoes. The potential for species-specific differences of larval behavior to contribute to discrepancies in surveillance data for mosquitoes inhabiting man-made wetlands also was studied in the laboratory. The behavior of the tule mosquito, CULEX ERYTHROTHORAX, differed significantly from that of three closely related species. CULEX ERYTHROTHORAX larvae dived less frequently but aggregated strongly in low light conditions and were comparatively sensitive to disturbances created while carrying out larval surveys than were the larvae of three closely related mosquito species. Larval mosquito surveys therefore underestimate the abundance of the tule mosquito and other surveillance methods will be needed in order to make
appropriate decisions for mosquito management in constructed treatment wetlands. Long-term selection studies demonstrated that the Cyt1Aa toxin from BACILLUS THURINGIENSIS ISRAELENSIS was the key protein responsible for the lack of resistance evolution in field populations of mosquitoes. Further, Cyt1Aa was found to mask the evolution of resistance to another bacterial insecticide, BACILLUS SPHAERICUS. Resistance was slowed and greatly reduced in mixtures containing Cyt1Aa compared to mixtures lacking that protein. These findings suggest that new recombinant strains of bacterial larvicides should contain Cyt1Aa to reduce the probability of resistance in mosquitoes when using this environmentally friendly approach for mosquito control.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands and natural wetlands as developmental sites. Accurate surveillance of vector abundance is required to provide information critical to decision-making for the management and prevention of vector-borne diseases. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction
Publications
- Walton, W. E. 2003. Managing mosquitoes at surface-flow constructed treatment wetlands. Publ. No. 8117. Univ. of Calif. Div. Agric. & Nat. Resources IPM Program, Davis. 11 pp.
- Wirth, M. C., W. E. Walton and A. Delecluse. 2003. Deletion of the Cry11A or the Cyt1A toxin from BACILLUS THURINGIENSIS subsp. ISRAELENSIS: effect on toxicity against resistant CULEX QUINQUEFASCIATUS (Diptera: Culicidae). Journal of Invertebrate Pathology 82: 133-135.
- Workman, P. W. and W. E. Walton. 2003. Larval behavior of four CULEX (Diptera: Culicidae) associated with treatment wetlands in the southwestern United States. Journal of Vector Ecology 28(2): 213-228.
- Sanford, M. R., J. B. Keiper and W. E. Walton. 2003. The relationship of drying period for harvested wetland vegetation to the abundance of mosquitoes and other invertebrates. Journal of the American Mosquito Control Association 19: 361-366.
- Keiper, J. B., J. A. Jiannino, M. R. Sanford, and W. E. Walton. 2003. Effect of vegetation management on the abundance of mosquitoes at a constructed treatment wetland in southern California. Proceedings of the Mosquito and Vector Control Association California 70: 35-43.
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Progress 01/01/02 to 12/31/02
Outputs
Whole body elemental composition of field-collected adult mosquitoes differed significantly among three CULEX mosquito species. Whole body nitrogen of adult mosquitoes was directly related to developmental rate and growth rate measured as the accumulation of dry body mass. The elemental composition of seston in developmental sites was similar to that found in the adult mosquitoes from constructed wetlands treating municipal wastewater, but differed markedly for mosquitoes utilizing agricultural wastewater ponds as developmental sites. The differences in the nutrient regimes and seston quality in aquatic habitats receiving municipal versus agricultural wastewater significantly affected the life history traits of CULEX mosquitoes reared in the laboratory in water from the two habitats. Two parallel, long-term selection projects designed to test the effect on resistance in CULEX QUINQUEFASCIATUS of combining the cytolytic toxin (Cyt1Aa) from BACILLUS THURINGIENSIS
ISRAELENSIS (BTI) with BACILLUS SPHAERICUS (BS) were continued. In addition to evaluating the effectiveness of toxin mixtures for resistance management of BS, we tested for interactions among microbial toxins to further investigate the phenomenon of toxin synergism that is responsible for the extremely high toxicity of this material. A comparatively more rapid progression of selection was observed in the resistant (Bsr-X) strain due to the presence of resistance genes which predisposed the strain to respond to selection pressure with BS. The second BS-susceptible strain, Syn-C, was more adversely affected by BS selection and exhibited a high rate of secondary mortality after the initial 48 hour exposure. Tests of the Bsr-X series initially showed a lower frequency of resistant mosquitoes in the line selected with BS and Cyt1A compared to the line selected with BS alone. However this difference disappeared in more recent tests. Long-term selection is needed to determine whether these
changes are transient. No change in resistance level has been detected in the Syn-C series to date. In our studies of toxin synergism, the results indicate that different Cry toxins of BTI can synergize BS and that the patterns of synergism differ between the mosquito species CULEX QUINQUEFASCIATUS and AEDES AEGYPTI.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands as developmental sites. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction of large-scale wetlands systems that will be designed to conserve precious water resources, promote the biodiversity of endemic wetlands organisms, and protect the public from mosquitoes and the diseases that they cause.
Publications
- Walton, W. E. 2002. Multipurpose constructed treatment wetlands in the arid southwestern United States: Are the benefits worth the risks? pp. 115-123. IN: J. Pries (ed.). Constructed Wetlands for Water Quality Improvement, CH2MHill Canada Limited, Pandora Press, Waterloo, ON.
- Keiper, J. B., D. L. Deonier, J. Jiannino, M. Sanford and W. E. Walton. 2002. Biology, immature stages, and redescriptions of HYDRELLIA PERSONATA Deonier (Diptera: Ephydridae), a LEMNA miner. Proceedings of the Entomological Society of Washington 104: 458-467.
- Thullen, J, S., J. J. Sartoris and W. E. Walton. 2002. Effects of vegetation management in constructed wetland treatment cells on water quality and mosquito production. Ecological Engineering 18: 441-457.
- Keiper, J. B. and W. E. Walton. 2002. Effects of three vegetation management strategies on shore-flies (Diptera: Ephydridae) in newly constructed treatment wetlands. Annals of the Entomological Society of America 95: 570-576.
- Keiper, J. B., W. E. Walton and B. A. Foote. 2002. Biology and ecology of higher Diptera from freshwater wetlands. Annual Review of Entomology: 47: 207-232.
- Walton, W. E., G. Peck and K. Chan. 2002. Factors regulating mosquito production at a renovated constructed treatment wetland. Mosquito Control Research Annual Report 2001. Univ. of Calif., Div. of Agric. & Nat. Resources, Berkeley, CA. pp. 41-45.
- Wirth, M. C., W. E. Walton, and B. A. Federici. 2002. Evaluation of alternative resistance management strategies for BACILLUS SPHAERICUS. Mosquito Control Research Annual Report 2001. Univ. of Calif., Div. of Agric. & Nat. Resources, Berkeley, CA. pp. 23-24.
- Federici, B. A., H-W. Park, A. Delecluse, D. K. Bideshi, B. Ge, J. J. Johnson, M. C. Wirth and W. E. Walton. 2002. Optimization of recombinant BTI/BS mosquito larvicides. Mosquito Control Research Annual Report 2001. Univ. of Calif., Div. of Agric. & Nat. Resources, Berkeley, CA. pp. 20-22.
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Progress 01/01/01 to 12/31/01
Outputs
The effects of mosquitofish (GAMBUSIA AFFINIS) on the aquatic insect community in a hypereutrophic constructed treatment wetland differed both spatially and among four cage treatments in an experiment. These results indicate both strong bottom-up regulation of the wetland ecosystem by nutrient loading and marked top-down effects of mosquitofish predation on wetland community structure. The four treatments in the experiment included screen (mesh size = 530 micrometers) cages without fish, cages containing 15-25 mosquitofish, 3-sided cages to control for changes in water flow by cages, and an ambient control without cages. Four blocks of treatments were placed both near the inlet and near the outlet of the wetland. Aquatic insect abundance in the inlet cages without fish was nearly three times higher than in the outlet cages without fish. A two-fold difference of zooplankton abundance observed in fishless cages in the inlet vs. the outlet was lessened markedly in
treatments where mosquitofish were present. On average, mosquito (CULEX spp.) abundance within the fishless cages was approximately 30- and 12-fold greater than in the inlet and outlet marshes of the wetland (ambient levels), respectively; whereas, ambient mosquito abundance in the inlet and outlet marshes containing the cages did not differ significantly across time. These results demonstrate that mosquitofish have an impact on mosquito abundance despite the presence of abundant alternate food resources and strong nutrient-driven effects in the food web. Two parallel, long-term selection projects designed to test the effect on resistance in CULEX QUINQUEFASCIATUS of combining the cytolytic toxin (Cyt1Aa) from BACILLUS THURINGIENSIS ISRAELENSIS (BTI) with BACILLUS SPHAERICUS (BS) are ongoing. In addition to evaluating the effectiveness of toxin mixtures for resistance management of BS, we tested for interactions among microbial toxins to further investigate the phenomenon of toxin
synergism that is responsible for the extremely high toxicity of this material. A comparatively more rapid progression of selection was observed in the resistant (Bsr-X) strain due to the presence of resistance genes which predisposed the strain to respond to selection pressure with BS. The second BS-susceptible strain, Syn-C, was more adversely affected by BS selection and exhibited a high rate of secondary mortality after the initial 48 hour exposure. Tests of the Bsr-X series showed a lower frequency of resistant mosquitoes in the line selected with BS and Cyt1A compared to the line selected with BS alone. No changes of resistance levels have been detected in the Syn-C series to date. In our studies of toxin synergism, the results indicate that the different Cry toxins of BTI also synergize BS.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands as developmental sites. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction of large-scale wetlands systems that will be designed to conserve precious water resources, promote the biodiversity of endemic wetlands organisms, and protect the public from mosquitoes and the diseases that they cause.
Publications
- Keiper, J. B., J. Jiannino, M. Sanford, and W. E. Walton. 2001. Biology and immature stages of TYPOPSILOPA NIGRA (Williston) (Diptera: Ephydridae), a secondary consumer of damaged stems of wetland monocots. Proceedings of the Entomological Society of Washington. 103: 89-97.
- Walton, W. E. 2001. Multipurpose constructed treatment wetlands in the arid southwestern United States: Are the benefits worth the risks? IN: J. Pries (ed.). Constructed Wetlands for Water Quality Improvement, Quebec 2000 Conference Proceedings. CH2MHill Canada Limited, Waterloo, ON.
- Walton, W. E. 2001. Effects of TRIOPS NEWBERRYI (Notostraca: Triopsidae) on aquatic insect communities in ponds in the Colorado Desert of southern California. Israel Journal of Zoology 47:
- Wirth, M. C., A. Delecluse, and W. E. Walton. 2001. Lack of cross-resistance to Cry19A from BACILLUS THURINGIENSIS subsp. JEGATHESAN in CULEX QUINQUEFASCIATUS (Diptera: Culicidae) resistant to Cry toxins from BACILLUS THURINGIENSIS subsp. ISRAELENSIS. Applied and Environmental Microbiology 67(4):1956-1958.
- Wirth, M. C., A. Delecluse, and W. E. Walton. 2001. Cyt1Ab1 and Cyt2Ba1 from BACILLUS THURINGIENSIS subsp. MEDELLIN and B. THURINGIENSIS subsp. ISRAELENSIS synergize BACILLUS SPHAERICUS against AEDES AEGYPTI and resistant CULEX QUINQUEFASCIATUS (Diptera: Culicidae). Applied and Environmental Microbiology 67(7):3280-3284.
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Progress 01/02/00 to 12/31/00
Outputs
Following renovation of a constructed treatment wetland to improve water nitrogen removal and reduce mosquito populations, the dynamics of the mosquitoes during 2000 differed markedly from the abundance trends observed during previous four years. During the three years of operation under the previous wetland configuration (80% of the water surface containing emergent vegetation) and during 1999 (the year after the renovation), host-seeking CULEX TARSALIS were collected from about late March through early November. In each year, the number of host-seeking females collected by carbon dioxide-baited traps declined beginning in October. In contrast to the pattern observed during the four aforementioned years, the C. TARSALIS host seeking population at the wetland exhibited a marked decline of about 4 orders of magnitude beginning during the last week of July and extending until the third week of September 2000. The mid-summer decline in mosquito abundance was also evident
in dip samples and emergence trap collections. After the first week of August 2000, larval mosquitoes and newly emerged adults were rare in 5 of the 7 marshes of the wetland. Two factors, predation and nutrient status, potentially influencing mosquito populations in the wetland changed during the summer. The number of mosquitofish collected by minnow traps increased two-fold during the summer. A decline in large-sized cladocerans preceded the decline in the mosquitoes and might have been indicative that mosquitofish switched from preying on zooplankton to mosquitoes as DAPHNIA populations declined in abundance. Water quality also improved during summer 2000. Influent ammonium-N concentrations declined from 19 MG/L to 7 MG/L after July 14. Effluent ammonium-N concentrations declined from 7.3 MG/L before July 14 to 1.8 MG/L after July 14. Total suspended solids in the effluent declined by 33% after July 14, even though algal biomass in September was about 10-fold higher than in May.
Based on the results of nutrient manipulations carried out at other wetlands, levels of ammonium-N comparable to that in the Hemet wetland effluent after July 14 did not sustain mosquito production. Long-term selection studies designed to test the effect of combining the cytolytic toxin (Cyt1Aa) from BACILLUS THURINGIENSIS ISRAELENSIS (BTI) with BACILLUS SPHAERICUS (BS) were carried out. Cyt1Aa played an important role in delaying and suppressing resistance to Cry toxins from BTI. We showed that Cyt1Aa suppressed high levels of resistance to BS and dramatically increased its toxicity against AEDES AEGYPTI, a species that is normally not susceptible to BS. The mechanism of resistance suppression and increased toxicity is synergism between the Cyt1Aa toxin and BS.
Impacts
The results of this study will help to provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands as developmental sites. Mosquito abatement and resistance management of mosquitoes to control agents must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands. The work summarized here will assist a multiagency effort to develop criteria for the construction of large-scale wetlands systems that will be designed to conserve precious water resources, promote the biodiversity of endemic wetlands organisms, and protect the public from mosquitoes and the diseases that they cause.
Publications
- Keiper, J. B., M. Sanford, J. Jiannino, and W. E. Walton. 2000. Invertebrates inhabiting wetland monocots by Lepidoptera. Entomological News 111(6): 348-354.
- Keiper, J. B. and W. E. Walton. 2000. Biology and immature stages of BRACHYDEUTERA STURTEVANTI (Diptera: Ephydridae), a hyponeustic generalist. Annals of the Entomological Society of America 93: 468-475.
- Wirth, M. C., B. A. Federici, and W. E. Walton. 2000. Cyt1A from Bacillus thuringiensis synergizes activity of BACILLUS SPHAERICUS against AEDES AEGYPTI (Diptera: Culicidae). Applied and Environmental Microbiology 66: 1093-1097.
- Wirth, M. C., W. E. Walton, and B. A. Federici. 2000. Cyt1A from BACILLUS THURINGIENSIS restores toxicity of BACILLUS SPHAERICUS against resistant CULEX QUINQUEFASCIATUS (Diptera: Culicidae). J. Med. Entomol. 37: 401-407.
- Workman, P. D. and W. E. Walton. 2000. Emergence patterns of CULEX mosquitoes (Diptera: Culicidae) at an experimental constructed treatment wetland in southern California. J. Am. Mosq. Control Assoc. 16: 124-130.
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Progress 01/01/99 to 12/31/99
Outputs
The second year of a study of three vegetation management strategies in small experimental wetlands was carried out during 1999. Compared to burning only, the use of hummocks to limit the proliferation of emergent vegetation reduced mosquito production during year 1 by more than 100-fold during the first three months of the study and by 98 percent across 1998. The marked differences in mosquito production observed among treatments during 1998 were lessened during 1999 as mosquito abundance increased directly with bulrush, SCHOENOPLECTUS CALIFORNICUS, growth. Mosquito production from wetlands containing hummocks was 53 percent that from the control treatment (burning only). Over two years, mosquito production was reduced by 60percent by incorporating hummocks into constructed treatment wetlands. Reduction of bulrush root densities following burning of dried emergent vegetation reduced mosquito abundance by approximately 10 fold during the three months after inundation
as compared to a treatment in which burning was the only vegetation management strategy; however, across 1998 mosquito production was 25percent of that from the control wetlands. During 1999, mosquito production from wetlands where bulrush root densities were reduced was equivalent to that from control wetlands. Averaged across the 2 years, mosquito production was reduced by only 15 percent following a 50 percentA reduction in bulrush root densities.
Impacts
The results of this study will help provide criteria for the management of pest and pathogen-transmitting mosquitoes that utilize constructed treatment wetlands as developmental sites. Mosquito abatement must be included as part of any comprehensive plan for the design and operation of multipurpose constructed treatment wetlands, particularly where human residences are situated near wetlands.
Publications
- Walton, W. E., K. Chan, L. H. Gould and L. Randall. 1998. Effects of vegetation management practices for constructed treatment wetlands on mosquito populations. Mosquito Control Research Annual Report. Univ. of Calif., Div. of Agric. & Nat. Resources, Berkeley, CA. pp. 58-61.
- Walton, W. E., L. Randall, J. Jiannino and J. B. Keiper. 1998. Influence of vegetation and dewatering on mosquito populations at a constructed treatment wetland. Mosquito Control Research Annual Report. Univ. of Calif., Div. of Agric. & Nat. Resources, Berkeley, CA. pp. 62-65.
- Walton, W. E., M. C. Wirth, and B. A. Federici. 1998. The effect of the CytA toxin ratio on the suppression of resistance and cross-resistance to mosquitocidal BACILLUS toxins. Mosquito Control Research Annual Report. Univ. of Calif., Div. of Agric. & Nat. Resources, Berkeley, CA. pp. 39-40.
- Keiper, J. B., J. Jiannino, J. Beehler and W. E. Walton. 1999. Distribution and abundance of Culicidae and Chironomidae (Diptera) following storm damage in a southern California constructed wetlands. Proc. Mosq. Vector Control Assoc. Calif. 67: In press.
- Offill, Y. A. and W. E. Walton. 1999. Comparative efficacy of the threespine stickleback (GASTEROSTEUS ACULEATUS) and the mosquitofish (GAMBUSIA AFFINIS) for mosquito control. J. Amer. Mosq. Control Assoc.: 15: 380-390.
- Walton, W. E., K. Chan, L. H. Gould and J. B. Keiper. 1999. Mosquito production from three vegetation management practices for constructed treatment wetlands: preliminary findings. Proc. Mosq. Vector Control Assoc. Calif. 67: In press.
- Walton, W. E., P. D. Workman, and J. B. Keiper. 1999. An inexpensive collapsible pyramidal emergence trap for the assessment of wetland insect populations. Proc. Mosq. Vector Control Assoc. Calif. 67: In press.
- Workman, P. D. and W. E. Walton. 2000. Emergence patterns of CULEX mosquitoes (Diptera: Culicidae) at an experimental constructed treatment wetland in southern California. J. Amer. Mosq. Control Assoc.: In press.
- Workman, P. D. and W. E. Walton. 1999. Adult spatial emergence patterns and larval behavior of the "tule mosquito" CULEX ERYTHROTHORAX. Proc. Mosq. Vector Control Assoc. Calif. 67: In press.
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Progress 01/01/98 to 12/31/98
Outputs
Mosquito production from two bulrush species (SCHOENOPLECTUS ACUTUS and SCHOENOPLECTUS CALIFORNICUS) in a constructed wetland was determined during spring 1998 and during dewatering in the early summer. Significantly more adult CULEX TARSALIS were produced from S. ACUTUS quadrats than were produced from S. CALIFORNICUS quadrats. Adult CULEX ERYTHROTHORAX production declined during dewatering and was two orders of magnitude lower than during a period of operation in the summer 1997. Host seeking mosquitoes continued to use the wetlands vegetation as resting sites even after water was drained from the wetland. The potential for arbovirus transmission between the wetland avifauna and the mosquito vectors remained high even though mosquito developmental sites were eliminated by draining the wetland. Three vegetation management strategies were studied in small experimental wetlands. Compared to burning only, the use of hummocks to limit the proliferation of emergent
vegetation reduced mosquito production by more than 100-fold during the first three months of the study. Reduction of bulrush root densities following burning of dried emergent vegetation reduced mosquito production by approximately 10 fold as compared to a treatment in which burning was the only vegetation management strategy. Laboratory studies of larval mosquito behavior showed that CULEX ERYTHROTHORAX larvae aggregated along vertical structures in comparatively dark areas of experimental arenas and were very sensitive to changes in light levels. The results from the laboratory studies and field studies examining the spatial distribution of adult emergence resolved an apparent discrepancy in the relative abundance of mosquito species in larval dip samples versus carbon dioxide baited trap samples of host seeking adults.
Impacts
(N/A)
Publications
- Walton, W. E., P. D. Workman, L. A. Randall, J. A. Jiannino, and Y. A. Offill. 1998. Effectiveness of control measures at a constructed wetland in southern California. J. Vector Ecol. 23: 149-160.
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Progress 01/01/97 to 12/01/97
Outputs
Mosquito production from two bulrush species (SCHOENOPLECTUS ACUTUS and SCHOENOPLECTUS CALIFORNICUS) in a constructed wetland was determined for July until October 1997. Significantly more adult CULEX TARSALIS were produced from S. ACUTUS quadrats than were produced from S. CALIFORNICUS quadrats. Adult CULEX ERYTHROTHORAX production was ten fold greater than for CULEX TARSALIS and was statistically equivalent throughout the wetland. The effectiveness of larvicide treatments against mosquitoes at a constructed wetland in San Jacinto, California was assessed via larval surveys, trapping of emerging adults and collections of host-seeking females by carbon dioxide-baited traps. BACILLUS THURINGIENSIS var. ISRAELENSIS was ineffective against CULEX spp. BACILLUS SPHAERICUS corn cob granules reduced larval populations from approximately 1 third-fourth instar larva per dip to undetectable levels within two to four weeks of the initial application. The CULEX ERYTHROTHORAX
host-seeking population declined about 80 fold at two weeks after the first treatment with B. SPHAERICUS. The marked decline in the host-seeking population in 1997 began 79 and 43 days earlier than in 1995 and 1996, respectively. The CULEX TARSALIS host-seeking population declined markedly during mid-October in 1995-97 suggesting that a photoperiodically induced cessation of host seeking (i.e., diapause) and immigration of females from other developmental sites might be important factors influencing autumnal host-seeking populations at the wetlands.
Impacts
(N/A)
Publications
- WALTON, W. E., P. D. WORKMAN, Y. OFFILL, L. RANDALL and J. JIANNINO. 1997. Influence of vegetation on mosquito production from a constructed wetlands Mosquito Control Research: Annual Report 1997. Univ. Calif. Div., Agric. Natur. Resources.
- WORKMAN, P. D. and W. E. WALTON. 1996. Biology and spatial distribution of mosquitoes in constructed wetlands. pp. 73-76. Mosquito Control Research: Annual Report 1996. Univ. Calif. Div.,
- OFFILL, Y. A., and W. E. WALTON. 1997. A comparison of two larvivorous fishes for mosquito control. Mosquito Control Research: Annual Report 1997. Univ. Calif Div., Agric. Natur. Resources,
- WALTON, W. E., M. C. WIRTH, P. D. WORKMAN and L. A. RANDALL. 1997. Survival of two larvivorous fishes in a multipurpose constructed wetland in southern California. Proc. Mosq. Vector Control Assoc.
- OFFILL, Y. A., and W. E. WALTON. 1998. A comparison of two larvivorous fishes, the stickleback (GASTEROSTEUS ACULEATUS) and the mosquitofish (GAMBUSIA AFFINIS), for larvicidal mosquito control. Proc. Mosq. Vector Control Assoc. Calif 66:.
- WALTON, W. E., and P. D. WORKMAN. 1998. Effect of marsh design on the abundance of mosquitoes in experimental constructed wetlands in southern California. J. Amer. Mosq. Control Assoc. 14: In press.
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Progress 02/01/96 to 12/30/96
Outputs
The efficacy of sticklebacks, GASTEROSTEUS ACULEATUS, as a biological control agent for mosquitoes inhabiting constructed wetlands was evaluated in small experimental wetlands in San Jacinto, CA. Sticklebacks were stocked into one half of the wetlands at a final rate of 0.75 kg per ha in late June and early July. Environmental stresses associated with an especially large die off of bulrush, SCIRPUS CALIFORNICUS, and secondary treated effluent may have contributed to the demise of the sticklebacks. Mosquitofish, GAMBUSIA AFFINIS, were unexpectedly found in one of the marshes. The restricted distribution and the failure of the population to proliferate suggest that conditions may also have been stressful for mosquitofish. The predominant mosquito captured as host-seeking females in the vicinity of the constructed wetlands, CULEX ERYTHROTHORAX, exhibited limited dispersal tendencies as compared to CULEX TARSALIS. More than 99% of marked CULEX ERYTHROTHORAX were
recaptured within 1 kilometer of the release point. The mean distance traveled was approximately 0.5 km per night. CULEX TARSALIS dispersed between 1.25 and 2 kilometers per night. The documented developmental site preferences of CULEX ERYTHROTHORAX for bulrush marshes and high survival of adults indicates that large populations can develop in the vicinity of constructed wetlands.
Impacts
(N/A)
Publications
- WALTON, W. E., P. D. WORKMAN and S. PUCKO. 1996. Efficacy of larvivorous fish against CULEX spp. in experimental wetlands. Proc. Mosq. Vector Control Assoc. Calif 64: 96-101.
- WALTON, W. E., and P. D. WORKMAN. 1996. Dispersal of CULEX mosquitoes from a constructed wetland in southern California. pp. 64-66. Mosquito Control Research: Annual Report 1995. Univ. Calif., Div. Agric. Natur. Resources, Berkeley, CA.
- WALTON, W. E., P. D. WORKMAN and S. PUCKO. 1996. Ecology and control of mosquitoes in constructed wetlands: effect of marsh design and the efficacy of an indigenous larvivorous fish. pp. 67-70. Mosquito Control Research: Annual Report 1995.
- WALTON, W. E., P. D. WORKMAN and S. PUCKO. 1996. Field evaluation of ovipositional attractancy for mosquitoes to constructed wetlands. pp. 71-72. Mosquito Control Research: Annual Report 1995. Univ. Calif, Div. Agric. Natur. Resources,.
- WALTON, W. E., M. C. WIRTH, P. D. WORKMAN and L. A. RANDALL. 1997. Survival of two larvivorous fishes in a multipurpose constructed wetland in southern California. Proc. Mosq. Vector Control Assoc.
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