Progress 10/01/10 to 09/30/15
Outputs
Target Audience:Mosquito and Vector Abatement Districts, U.S. Fish and Wildlife contaminants scientists and refuge managers, CA State Department of Pesticide Regulation personnel, CAL EPA, CA Parks and Recreation, USDA scientists, members of the public. The broader target audience includes scientists or habitat managers nationally and worldwide who require information on best practices for managing freshwater aquatic ecosystems to enhance natural resources while minimizing mosquito abundances and invasive aquatic taxa. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project provided training for junior specialist Joel Hernandez, Ph.D. graduate students Maribel Portilla, Sarah Stinson and Simone Hasenbein, and also post-doctoral training for Dr. Hasenbein. Each year the project also provided research experience for 2-4 undergraduate interns. How have the results been disseminated to communities of interest?In addition to the publications produced, results have been communicated to stakeholders through a variety of presentations. In addition to talks reported in earlier years of this project, Lawler gave an invited talk on Mosquito Ecology and Aquatic Weeds to the Central California Mosquito and Vector Abatement Districts (Agricultural Commissioner's Office, Stockton, CA, 11/05/2014, ~80 Attendees). Lawler gave an invited symposium talk to a variety of entomologists from industry, management and academia on 'Efficacy, non-target effects and other considerations for microbial and other non-traditional mosquito larvicides (Symposium title and information: Novel Ecological Approaches to Vector Control, Entomological Society of America Nov. 19,2014, Portland, OR). Lawler contributed a talk on 'New Knowledge on Weed-Mosquito Interactions to Improve Mosquito Control in Areas of Public Health Concern' at a Stakeholder and Scientist Meeting for the Area-Wide Project on Aquatic Weeds of the Sacramento-San Joaquin Delta (2015 August 28. Robert J. Cabral Agricultural Building, San Joaquin, CA). Simone Hasenbien gave a presentation about this project to at the Bay-Delta Science Conference, Oc. 28-30, Sacramento Convention Center. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
PURPOSE AND OVERALL GOALS. Control of pathogen-vectoring mosquitoes is of great importance because several mosquito-borne pathogens can damage the health and well-being of humans, livestock, and wildlife. Changing climatic conditions are extending mosquito breeding and allowing new mosquitoes and pathogens to invade California and the USA. Encephalitis viruses, dog heartworm, and other mosquito-borne pathogens are endemic and the region is vulnerable to invaders like Japanese Encephalitis Virus and Rift Valley Fever Virus. Stakeholders consider it important to choose mosquito control methods that minimize impacts on non-target species: these include the public, land managers, and agencies responsible for mosquito and vector control, environmental protection, and wildlife protection. Research is needed to quantify the effectiveness and potential environmental impacts of mosquito control. Therefore, the two aims of this project were to: 1. Evaluate the environmental effects and effectiveness of existing and emerging mosquito control techniques, especially microbially-derived larvicides. 2. Quantify how management of permanent wetlands affects mosquito production and aquatic food webs. SUMMARY OF PROGRESS DURING PRIOR REPORTING PERIODS. Specific studies changed during the project because a funded contract on mosquito production in carbon storage wetlands was cancelled due to the recession, and because a project on how mosquito control affects fairy shrimp failed to attract funding. We obtained funding from the Mosquito Research Foundation, California Department of Pesticide Regulation, and the State and Federal Contractors Water Agency for studies that fell under our aims. The first was research on the efficacy of VectoMax (Valent BioSciences) against mosquitoes in wetlands; it is a combined formulation of two microbial larvicides, Bacillus thuringiensis israelensis and Lysinibacillus sphaericus. A replicated field experiment showed that this formulation yielded extended control of Culex mosquitoes (Dritz et al. 2011). The second study was a mesocosm experiment that quantified efficacy and non-target effects of larvicides derived from the microbe spinosad (Lawler et al. 2013). Liquid and granular formulations of spinosad yielded excellent control of Culex mosquitoes. However, most taxa of non-target aquatic invertebrates also decreased in abundance in treated mesocosms. The third set of studies quantified how pesticides applications singly and in mixtures affected the survival, behavior, and community dynamics of aquatic invertebrates. Aquatic communities often receive mixtures of contaminants. Pesticides tested included permethrin, which is commonly used in mosquito control. Chemicals within mixtures can either act additively on non-additively (synergistically or antagonistically). We investigated the mixture effects of two pyrethroids, lambda-cyhalothrin and permethrin, and the organophosphate chlorpyrifos by assessing survival , motility and growth of the midge Chironomus dilutus in 10-day laboratory exposures (Hasenbein, Lawler, Geist and Connon 2015). Increased immobility resulted from mixture concentrations at 7.45 ng/L lambda-cyhalothrin x 24.90 ng/L permethrin x 129.70 ng/L chlorpyrifos, and single pesticides concentrations at 5.50 ng/L lambda-cyhalothrin, 24.23 ng/L permethrin, and 90.92 ng/L chlorpyrifos, respectively. Growth was inhibited by a mixture of 1.04 ng/L lambda-cyhalothrin x 3.15 ng/L permethrin x 15.47 ng/L chlorpyrifos, and singly by lambda-cyhalothrin at 5.50 ng/L and by permethrin at 18.21 ng/L. PROGRESS IN 2014-2015. We continued work on the single and combined effects of pesticides with a focus on aquatic indicator taxa including the midge C. dilutus, and the scud H. azteca. Midges and scuds are important food for fishes, and birds. To fill in gaps in the literature we used 10-day exposures to assess the effects of pesticides applied singly: bifenthrin, permethrin, cyfluthrin, and chlorpyrifos. We recorded survival, motility and growth (Hasenbein, Connon, Lawler and Geist, 2015). Pyrethroids were more toxic than the organophosphate chlorpyrifos. Bifenthrin and cyfluthrin caused high mortality of H. azteca at levels between 1-10 ng/L and cyfluthrin caused over 40% mortality at the 10 ng/L level in C. dilutus; these levels are similar to those found in some waterways. Permethrin and chlorpyrifos caused little mortality until concentrations were ~40 ng/L or more. However, all pesticides had detectable sublethal effects at just a few ng/L, especially for H. azteca. Motility was the most sensitive endpoint for assessing sublethal effects for both species, and growth was a good indicator of toxicity for all pesticides for H. azteca. The use of sublethal endpoints in water monitoring could improve identification of low-level pesticide concentrations that cause negative effects on aquatic food webs. Research was also needed to assess whether pesticide mixture effects found in the laboratory translate into population losses in the field. We used outdoor mesocosms to examine effects on aquatic invertebrate communities of mixtures of some of the most common pesticides found as contaminants: 2 pyrethroids (permethrin, lambda-cyhalothrin) and an organophosphate (chlorpyrifos) (Hasenbein, Lawler, Geist and Connon 2016). Application rates were based on either average concentrations found in contaminated California waters , or stepwise increases across the summer of lethal concentrations from 10% (LC10) to 50% (LC50) based on laboratory tests on H. azteca and C. dilutus. The repeated applications were meant to imitate runoff events in watersheds that are subject to applications by growers, homeowners, and mosquito control technicians. Abundances of 12 macroinvertebrate taxa (of 15 present) and ten of 16 zooplankton taxa were negatively affected by the contaminant exposures. The most sensitive taxa were the snail Radix., the amphipod H. azteca, the water flea Daphnia magna, and copepods. Environmentally-relevant concentrations decreased abundances of D. magna and H. azteca immediately after application, whereas lag times were more pronounced in Radix sp. snails and copepods, indicating chronic sublethal responses. Worryingly, the largest effects on zooplankton communities were observed in environmentally relevant concentration treatments. Finally, in 2014, the U.S. Department of Agriculture funded us to research how aquatic weeds and weed control affect mosquito abundances in the Sacramento-San Joaquin Delta. This allowed us to begin research on management of mosquitoes in permanent wetland habitats. The research is ongoing as part of our new project. SUMMARY. The project yielded five publications in the peer-reviewed scientific literature that advanced understanding of the effectiveness of insecticides used in mosquito control and their non-target effects. It contributed to training several junior scientists and formed the dissertation research of Dr. Simone Hasenbein, it built institutional collaborations among U.C. Davis, CA-Department of Pesticide Regulation, USDA, county Mosquito and Vector Control Agencies (e.g., Solano, Sacramento-Yolo, San Joaquin, Contra Costa) and habitat managers (e.g., CA Fish and Game). Throughout the project, we communicated the results of our studies to numerous stakeholders including habitat managers, various agency personnel, and public stakeholders through scientific and public meetings.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2015
Citation:
Hasenbein, Simone, Richard E. Connon, Sharon P. Lawler and Juergen Geist. A comparison of the
sublethal and lethal toxicity of four pesticides in Hyalella azteca and Chironomus dilutus.
Environmental Science and Pollution Research, 22(15): 11327-11339.
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Hasenbein, Simone, Sharon P. Lawler, Juergen Geist and Richard E. Connon. A long-term
assessment of pesticide mixture effects on aquatic invertebrate communities. Environmental
Toxicology and Chemistry, 35(1): 218-232.
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Progress 10/01/13 to 09/30/14
Outputs
Target Audience: Mosquito and Vector Abatement Districts, U.S. Fish and Wildlife contaminants scientists and refuge managers, CA State Department of Pesticide Regulation personnel, CAL EPA, CA Parks and Recreation, USDA scientists, legislators from Stockton and Contra Costa counties, NASA scientists. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? As detailed in last year's report, this project has provided training in ecotoxicology, plus professional development for Project Leader Simone Hasenbein, a Ph.D. student. Another Ph.D. student began training via this project in 2014: Ms. Erin Donley Marineau. Ms. Marineau is now our project leader for assessing how aquatic weeds such as water hyacinth, Brazilian waterweed, and Eurasian water milfoil affect aquatic invertebrates, including mosquito populations. Several early-career scientists are participating in the project as technicians (Theresa Totah, Joel Hernandez, and Matt Perryman), and we are also working with Rakim Turnipseed, a Ph.D. student at U.C. Berkeley. Three out of these four are from groups underrepresented in the sciences. How have the results been disseminated to communities of interest? In addition to the Continuing Education and Symposium talks listed above, Lawler participated in Simone Hasenbein's presentation of her results on pesticide mixtures to the California Environmental Protection Agency 8/23/2014. Lawler presented the project on aquatic weeds and mosquitoes to numerous agencies, legislators, and public boating groups at a December 17th meeting at the San Joaquin Agricultural Commissioners office (e.g., local citizens, County Supervisors, congressional aides, CA Fish and Wildlife, NASA, Parks and Recreation, Bureau of Land Management, CA Water Resources, US Bureau of Reclamation, the Delta Stewardship Council, Sacramento-San Joaquin Delta Conservancy and etc). What do you plan to do during the next reporting period to accomplish the goals? Plans for this year include publishing the results of our research on pesticide mixtures in wetland mesocosms, and designing and executing a field experiment on how aquatic weed removal using chemicals versus harvesting affect mosquitoes, their predators, and their competitors. In addition we will perform a survey aimed at quantifying the relationship between various aquatic weed species and mosquito populations. Finally, if funded, we will initiate a survey of wetlands developed for carbon storage and other permanent, heavily-vegetated wetlands with the goal of predicting mosquito control needs for carbon mitigation projects.
Impacts
What was accomplished under these goals?
The two overarching goals of this project are: 1. To evaluate the environmental effects and efficacy of existing and emerging mosquito control techniques, especially microbially-derived larvicides, and 2. To quantify how the establishment and management of permanent wetlands affects mosquito production and aquatic food webs in these habitats. In 2014 we completed our work on microbial larvicides. This culminated in an invited symposium talk to the Entomological Society of America that produced changes in knowledge among scientists and policymakers, some of whom were unfamiliar with the efficacy and safety of mixtures of Bacillus thuringiensis israelensis and Bacillus sphaericus, and most of whom were not aware of the deleterious effect of spinosyns on aquatic invertebrates. The bulk of our work in 2014 was directed to two additional two specific goals: to address how mixtures of broad-spectrum insecticides affect the survival and behavior of aquatic invertebrates, and to prepare new studies on quantifying mosquito production from aquatic weed beds in California's delta region. An outstanding specific objective is `to quantify mosquito production from permanent wetlands established for soil restoration and carbon banking'. Funding was cancelled in 2010 due to government cuts, however in 2014 S. Lawler participated in a proposal on this topic to CA Fish and Wildlife, as a Co-PI with scientists from U.C. Berkeley and Hydrofocus, Inc.. A major activity during this period was to complete our research on comparing the toxicities of single pesticides and pesticide mixtures on aquatic scuds (Hyalella azteca) and/or midge larvae (Chironomus dilutus). A paper on the toxicity of pesticide mixtures has been accepted in Ecotoxicology, and another was submitted to Environmental Science and Pollution Research that compared the reactions of scuds and midges to three major pesticides, lambda-cyhalothrin, permethrin, and chlorpyrifos. This and our related work in field mesocosms also have been submitted to CA Department of Pesticide Regulation (CA DPR) as an interim reports. Freshwaters in the USA are often contaminated with mixtures of pesticides from agriculture, home and lawn maintenance, and mosquito control. We quantified how a three-part mixture of lambda-cyhalothrin (used in agriculture), permethrin (agriculture and mosquito control), and chlorpyrifos (agriculture, termite control) affected growth, behavior (motility), and survival of Chironomus dilutus in 10-day exposures. We utilized a toxic units (TU) approach, based on median lethal concentrations (LC50) for each compound. We tracked both lethal and sublethal endpoints, because our single-species work (see below) showed that the latter were much more sensitive indicators of contaminants. Motility was the most sensitive, followed by growth, and then mortality. The no observed effect concentrations (NOEC) for immobility and growth, for both mixture and single-pyrethroid exposure, were up to 8.0 and 12.0 times respectively lower than the corresponding NOEC for survival. The median effective concentrations (EC50) for growth were up to 7.0 times lower than the respective LC50. We included research on individual pesticides that was directed at filling critical information gaps regarding their sublethal effects. In 10-day exposures, we assessed the lethal and sublethal (motility and growth) toxicities of four commonly used pesticides, bifenthrin, permethrin, cyfluthrin, and chlorpyrifos, on two freshwater invertebrates, Chironomus dilutus and Hyalella azteca. Pyrethroids were more toxic than the organophosphate chlorpyrifos in both species. Bifenthrin was most toxic to H. azteca survival and growth (LC50-Survival 2.01 ng/L, EC50-Weight 1.65 ng/L). Cyfluthrin was most toxic to C. dilutus (LC50-Survival 17.36 ng/L, EC50-Weight 14.48 ng/L). Cyfluthrin had the greatest effect on motility on both H. azteca and C. dilutus (EC50-Motility 0.53 ng/L and 4.81 ng/L, respectively). The evaluated concentrations of chlorpyrifos did not affect C. dilutus motility nor growth, but impacted H. azteca growth (EC50-Growth 25.08 ng/L). Motility served as the most sensitive endpoint in assessing sublethal effects at low concentrations for both species, while growth was a good indicator of toxicity for all four pesticides for H. azteca. The integration of sublethal endpoints in ambient water monitoring and pesticide regulation efforts could improve identification of low-level pesticide concentrations that may cause negative effects on food webs and community structure in aquatic environments. Laboratory toxicity may not reliably indicate field toxicity due to differences in exposure or because laboratory animals may differ from field strains (due to differences in natural selection, source population, acclimatization or other reasons). Research was needed to understand the toxicity of pesticide mixtures under more realistic conditions. We therefore created artificial ponds in outdoor 1000 L cattle-watering tanks with natural substrates, to allow for insects to colonize. We exposed our study organisms, as well as ambient invertebrates, to the effects of two pyrethroids; lambda-cyhalothrin and permethrin (used in mosquito control), and one organophosphate; chlorpyrifos. We added Chironomus dilutus and Hyalella azteca (test taxa. Pesticides were applied to mesocosms either at lethal concentrations relative to one of the test taxa, or at concentrations derived from field studies of California waters. The effects of a series of applications of tertiary contaminant mixtures resulted in significant decrease in populations of H. azteca, Zygoptera (damselflies), and the zooplankton taxa Copepoda and Cladocera. The lethal concentrations determined in single-species tests in the laboratory did not necessarily reflect the effects predicted in the environment. Levels that were moderately toxic to laboratory H. azteca rarely caused detectable effects, however some population decreases were noted for the environmentally-relevant treatment and many were noted for higher concentrations based on C. dilutus toxicity, both of which contained higher amounts of lambda-cyhalothrin. Lambda-cyhalothrin was one of the most toxic pesticides in our prior laboratory test, and in S. Lawler's past work. On another note, our failure to detect synergistic effects of the pesticides is somewhat encouraging, because possible synergisms have been of great concern due to the multiple contaminants that now affect many freshwater systems. In a new study for this project, ecological and interactions between mosquitos and invasive aquatic plants in permanent waters of the CA Delta region are being investigated by S. Lawler and M. P. Parrella collaboration with USDA-ARS and the Contra Costa and San Joaquin Mosquito and Vector Control Districts (MVCDs). Two USDA-ARS Pathways Ph.D. students (Rakim Turnipseed and Erin Donley Marineau) are contributing to these studies. Participants from UC Davis, the MVCDs, USDA-ARS, and Parks and Recreation met in September and December to select study sites and to discuss experimental designs, with the goal of developing `best practices' control methods and a system of prioritizing sites for treatment. Quantitative studies are needed to assess methods for weed control that do not worsen mosquito problems by impacting beneficial predators, for example through oxygen depletion from decomposing vegetation. To discover associations between mosquitoes and weed extent and diversity, three sites were surveyed repeatedly in 2014 (Mosher Slough, White Slough, and Upland Canal) and eight additional locations are scheduled for study in 2015.
Publications
- Type:
Journal Articles
Status:
Accepted
Year Published:
2015
Citation:
Hasenbein, S., S.P. Lawler, J. Geist and R. Connon. The use of growth and behavioral endpoints to assess the effects of pesticide mixtures upon aquatic organisms. Ecotoxicology.
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Mosquito and Vector Abatement Districts, U.S. Fish and Wildlife contaminants scientists and refuge managers, CA State Department of Pesticide Regulation personnel, pest control industry environmental managers and sales personnel. Changes/Problems: The project was broadened to include research on the toxicity of pesticide mixtures. This approach enabled us to secure funding through the State and Federal Contractor's Water Agency via CA DPR, thus we have been able to continue assessment of insecticides used to protect public health. What opportunities for training and professional development has the project provided? This study has provided training and professional development for Project Leader Simone Hasenbein, a Ph.D. student. She has learned numerous techniques in bioassays, pesticide analysis, and field ecology.She co-authored the proposal for the project and presented results at local and national conferences. In addition two undergraduate interns worked on the project and learned field techniques in ecotoxicology. How have the results been disseminated to communities of interest? Results of the spinosad project were disseminated via a publication, last year's presentation at the Mosquito and Vector Control Association of California Annual Meeting, this year's presentation at the American Mosquito Control Association, and via email to scientists and managers at the US Department of Fish and Wildlife and various Mosquito and Vector Control Districts. Results of the pesticide mixture project were presented to the California Department of Pesticide Regulation as an Interim Report, and to ecotoxicologists at the annual meeting of the Society for Environmental Toxicology and Chemistry. What do you plan to do during the next reporting period to accomplish the goals? Plans for this year include publishing the results of the laboratory research on pesticide toxicity, and completing, publishing, and presenting our research on pesticide mixtures in wetland mesocosms. In addition we will seek funding and collaborators for new projects on the non-target effects and efficacy of mosquito control techniques.
Impacts
What was accomplished under these goals?
The first stated goal of this project is to evaluate the environmental effects and efficacy of existing and emerging mosquito control techniques. A major activity during this period was to write up the results of our prior work on spinosad-based insecticides used in mosquito control; this work and its results were described in last year's report and the result is that the research is now published in a peer-reviewed journal. We showed that spinosad-based insecticides were highly effective against mosquito larvae, but that there was also toxicity to a variety of other aquatic insects. Mosquito abatement managers and wildlife managers are now able to use this knowledge in making pesticide use decisions. My collaborators, myself, and our project leader Simone Hasenbien are currently researching the environmental effects of additional pesticides. Flowing waters and associated sediments may be contaminated by a variety of pesticides used in mosquito control and agriculture. Non-target tests are performed routinely as part of the pesticide registration process; however, we discovered information gaps on the toxic effects of several materials. Not only are their information gaps on individual pesticides, pesticide mixture effects are a concern but their effects are rarely explored. The California Department of Pesticide Regulation contracted with us to quantify individual and mixture toxicities of permethrin, bifenthrin, cyfluthrin, lambda-cyhalothrin and chlorpyrifos, to standard freshwater test species, the scud Hyalella azteca and the midge Chironomus dilutus. Permethrin is the only one of these widely used by mosquito and vector control districts. However, all others except for chlorpyrifos are marketed to homeowners for outdoor insect control, including mosquito control. A major activity was to measure mortality and sublethal effects on motility and growth for both test species. We performed ten-day toxicity tests using a dilution series of individual pesticides. Results showed that H. azteca were more sensitive than C. dilutus to all of the insecticides. Sublethal effects, however, were more pronounced in C. dilutus, and occurred at levels down to one ninth of the 50% lethal effect concentrations (LC50). Lambda-cyhalothrin caused the greatest effect on C. dilutus motility, with as low as 38% mean swimming velocity relative to the control, followed by permethrin (47%), and chlorpyrifos (55%) at sub-lethal concentrations. Ten-day growth was as low as 24% of the control for bifenthrin and lambda-cyhalothrin, 33% for cyfluthrin, and 37% for permethrin. H. azteca growth was not detectably affected by most of the pesticides. Motility was affected, but predominantly at levels near the lethal concentration. The exception was bifenthrin, which inhibited H. azteca growth at the picogram concentration level. Across the tested pesticides, sublethal responses in H. azteca, were decreased to 34-70% of mean swimming velocity and 33% mean 10-day growth compared to controls. Conclusions were that patterns in lethal and sublethal responses are not predictable across species, and now regulators will have better information on the comparative toxicity of these major pesticides. Moreover, some of the pesticide levels showing harm are found in a number of California waterways. This work is being prepared for publication. In a second major activity, we tested environmental effects of pesticide mixtures in the summer of 2013. We constructed artificial ponds next to a wetland in the spring, and allowed them to be colonized by aquatic invertebrates. We introduced populations of H. azteca and zooplankton, which were less likely to colonize quickly because they do not have a winged stage. These mesocosms were exposed to mixtures of several of the most common pesticides found in streams and rivers: permethrin, lambda-cyhalothrin, and chlorpyrifos. One set of replicates were unexposed, another was exposed to five treatments of typical environmental levels, and two sets were exposed to five treatments that gradually increased from LD 10 levels of all materials to LD50 levels of all materials. Of these latter sets, the first toxicity levels were based on the H. azteca trials discussed above, and the second on the C. dilutus trials. Preliminary results showed little if any effect of mixtures of LD10 levels. However, there were fewer H. azteca in mesocosms that had two applications of LD 25 levels versus controls, and toxicity was also associated with higher levels or repeated applications of the environmental concentration. Only a fraction of taxa have been enumerated and this work will be completed in the coming year.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Lawler, S.P. and D. A. Dritz. 2013. Efficacy of Spinosad in Control of Larval Culex tarsalis and Chironomid Midges, and Its Nontarget Effects. Journal of the American Mosquito Control Association 29(4):352-357
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: In 2012 we performed an experimental study of the efficacy and non-target effects of Natular, a mosquito larvicide based on the bacteria spinosad. We performed the study in 15 wetland mesocosms to quantify the effects of mid- to high- label rates on Culex tarsalis mosquitoes and a variety of other aquatic invertebrates. Five mesocosms received a mid-label dosage of the granular G30 Natular, five received maximum label rates of the liquid 2EC Natular, and five were untreated controls. Our project was collaborative with the manufacturer, Clarke, two mosquito and vector control districts (Sacramento-Yolo MVCD, Sutter-Yuba MVCD), and US Fish and Wildlife and wildlife managers at Roosevelt Ranch provided space or organisms for the study. Thus three kinds of stakeholders were well informed about our study and its results. Results have been disseminated as an oral presentation to the Mosquito and Vector Control Association of California. Continuing education credits were awarded to many who attended this conference. A manuscript is in preparation. PARTICIPANTS: This project was made possible by funding from the Mosquito Research Foundation. Staff Research Associate Deborah Dritz partnered with PI Sharon Lawler in all aspects of the work. Roosevelt Ranch (Manager Brian Olson) provided space for the work and practical assistance, Mike Fike of Sac-Yolo MVCD applied the material, Deborah Lemanager of Sutter Yuba MVCD supplied mosquito larvae, Grifith Lizarraga and Jake Hartle of Clarke assisted with study design and execution. Mike Wolder of US Fish and Wildlife assisted with mayfly collection, and Pleasant Grove Farms allowed us to collect mayflies from their organic rice fields. Two undergraduate interns obtained research experience during this project: Joel Hernandez and Erin Barry. TARGET AUDIENCES: Target audiences for this work include public and private mosquito control organizations in California and similar professionals worldwide who need information on the effectiveness and environmental impacts of insecticides used in mosquito control. Wildlife agencies and environmentalists also require information on the impacts of mosquitoes and insecticides on human health and the environment. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Our mesocosm study showed that the liquid formulation of Natular (spinosad) had efficacy of unusual duration under our clean-water study conditions; it controlled mosquito larvae for several weeks although it is a single-brood formulation. The granular formulation was effective for up to 35 days. Mayfly larvae were used as a representative non-target species. These were less sensitive to the insecticide than were mosquitoes, but showed substantial mortality of 60-85% for up to three weeks. Other non-target insects were significantly scarcer in treated mesocosms than in controls for up to 35 days. The duration of the non-target effect may in part be due to the time needed for recolonization after the initial mortality event. In total the work showed that Natular had some non-target effects under study conditions, and that it was highly effective against Culex tarsalis, a vector for West Nile Virus and other pathogens. Further work is needed with other rates and conditions.
Publications
- Lawler, S.P. and D.A. Dritz. 2013. Efficacy of Natular 2EC and G30 Formulations Against Culex tarsalis, and Non-target Effects. Mosquito and Vector Control Association of California Annual Meeting (abstract), Feb 3-6, Hyatt Sacramento, Sacramento, CA.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: For 2011 we planned to study the non-target effects of three materials used for mosquito control, spinosad, Bti, and Bs. We also planned to write up our prior research on the efficacy of VectoMax against mosquitoes. Our project suffered a reversal in 2011 with delays or cancellation of the funding for the non-target studies. Therefore we invested much of our research time in writing proposals: these outputs included a proposal to the mosquito research foundation, a proposal to industry, a pre-proposal and a proposal to UC ANR, and a revised proposal to US Fish and Wildlife. We have secured a promise of increased funds through the Mosquito Research Foundation for the spinosad work, and are actively planning that work for this year. We also wrote up results on our study of the efficacy against larval mosquitoes of VectoMax (a combined formulation of Bti and Bs), and disseminated findings to mosquito abatement personnel in the form of two presentations, one to vector control districts and another to the Northern California Entomology Club. Results were also disseminated as a journal article. PARTICIPANTS: Deborah A. Dritz, Staff Research Associate, UC Davis. Carol Evkhanian, Vic Baracosa, Gary Dula, Staff, Solano Mosquito Abatement District Patrick Graham, California Department of Fish and Game, Grizzly Island Wildlife Area TARGET AUDIENCES: The target audiences for this work are mosquito and vector control districts in California and similar professionals worldwide, who wish to improve both the effectiveness of mosquito control. These stakeholders also strive to protect the environment via use of mosquito abatement techniques with limited non-target effects. Other audiences include a variety of wildland and wetland managers who are also interested in mosquito control and environmental stewardship. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Our analysis of the data on the efficacy of VectoMax showed that it was effective against Culex tarsalis mosquito larvae for up to four weeks, and it showed a trend toward controlling Oc. melanimon larvae as well. Mosquito and Vector Control districts have found this information useful in planning their integrated pest management programs. This project will lead to wider adoption of VectoMax, which reduces the need to apply broad-spectrum insecticides. At the same time broader use of this material will reduce the risk that resistance to either of its component materials will emerge in mosquitoes.
Publications
- Dritz, D. A., S. P. Lawler, C. Evkhanian, P. Graham, V. Baracosa and G. Dula. 2011 in press. Control of mosquito larvae in seasonal wetlands on a wildlife refuge using VectoMax. Journal of the American Mosquito Control Association 27(4).
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: The purpose of this research is to advance understanding of mosquito ecology, and to test the effects of mosquito control on non-target species. Mosquito and Vector Control Districts (MVCDs) control mosquitoes which can transmit diseases and create pest problems for humans and livestock. However, conservationists and public agencies such as the U.S. Fish and Wildlife Service (USFWS) are concerned that mosquito control techniques may harm non-target species, especially endemic protected taxa like fairy shrimps. There is also a need to understand how agricultural and restored wetlands affect the prevalence of mosquitoes. These are increasingly common on the landscape, especially along the Sacramento and San Joaquin rivers and in the Delta. We proposed three studies to be completed during the project period. Specific objectives are 1. To quantify the effects of mosquito larvicide formulations of Bti (Bacillus thuringiensis israelensis) and Bs (Bacillus sphaericus) on endemic fairy shrimp, 2. To test the efficacy and non-target effects of the larvicide spinosad on mosquito and midge larvae and other aquatic fauna., 3. To quantify mosquito production from permanent wetlands established for soil restoration and carbon banking.
We are in the developmental stages of this project. Field work for # 1 is beginning in Feb 2011. Our field work on # 3, scheduled for last year, was cancelled due to suspension of the CA State contract that was funding it. In 2010 - Jan 2011, we submitted proposals to seek funding for all objectives as follows. The first was with US Fish and Wildlife through Cathy Johnson to fund research on how bacterial mosquito larvicides affect fairy shrimps, the second was with the Mosquito Research Foundation of the Mosquito and Vector Control Association of California to fund work on the non-target effects of spinosad (a back-up grant was recently submitted to CA LCC through C. Johnson and USFWS), and the third was to USDA through Steve Deverel of HydroFocus, Inc, to fund research on how carbon restoration wetlands affect mosquito populations in the Delta region of California (the original PI Roger Fujii approved our collaboration with Deverel because funding had not been restored).
Research plans for BTI/BS were disseminated to USFWS, Solano Mosquito Abatement, and Valent BioSciences via a written research proposal, meetings and telephone calls. Research plans for spinosad were disseminated to the Mosquito Research Foundation through a written proposal, an oral presentation at the CMVCA conference, and via email. A similar project was submitted to USFWS and CA LCC as a written proposal. Research plans for carbon restoration wetlands were disseminated to USDA and HydroFocus, Inc. through a written proposal and email. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: The scope of the project on how carbon restoration wetlands may affect mosquito populations has been reduced due to greater funding limitations for the project. We no longer plan to sample the predators and competitors of mosquitoes extensively, rather we will quantify only those appearing in dip samples for mosquitoes.
Impacts
The impact of this project has been to raise awareness of potential non-target effects of mosquito control with wildlife agencies and mosquito and vector control districts (Objectives 1 &2).
Publications
- No publications reported this period
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