How to Manage Pests

Mosquitoes

Managing Mosquitoes in Surface-Flow Constructed Treatment Wetlands Section 4: Recommendations for Enhancing Mosquito Abatement Efforts in Constructed Wetlands, and Conclusion Published 2004 Sections of this publication:
Introduction Treatment Wetland Siting and Pretreatment to Minimize Mosquito Production Treatment Wetland Design and Operation Recommendations for Enhancing Mosquito Abatement Efforts in Constructed Wetlands, and Conclusion Bibliography For More Information

• Incorporate wide embankments to allow drivable shoreline access to all wetland cells. Access should have adequate turning areas. If cells exceed approximately 20 feet (6 m) wide, vehicular access to both sides must be provided. These embankments should have a top width of no less than 13 feet (4 m) and should have side slopes no steeper than 4:1 to allow access for mowing and sampling.
• Incorporate deep-water zones that are free of emergent and aquatic plants. Nearly vertical edges at the perimeter of the wetland limit the growth of emergent vegetation but may pose a safety concern.
• Provide access structures with appropriate slopes to cross deep-water zones. Boats or amphibious vehicles can be launched into these zones for application of mosquito control agents.
• Keep embankments and all wetland areas free of power lines, trees, and other tall vegetation and obstructions that might limit aerial spraying.
• Limit the width of emergent plant zones to facilitate access by predaceous fish and for application of chemical control agents.
• Compartmentalize the wetland so that the maximum width of ponds does not exceed two times the effective distance (40 feet [12 m]) of land-based application technologies for mosquito control agents. This design feature should reduce the costs of mosquito abatement by focusing mosquito abatement on small regions of the wetland and eliminating the need to apply mosquito control agents by aircraft.
• Minimize fluctuations in water level to prevent large areas of intermittently flooded substrate or isolated pools from being created, particularly during the period of annual mosquito activity (April to November in most regions of California).
• Budget for periodic vegetation maintenance and vector control.
• Have an emergency plan that provides for immediate drainage into acceptable areas if a public health emergency occurs.

Operating a wetland represents a long-term commitment to wetland maintenance and mosquito control and also exposes the managing organization to potential legal liability. The decision to proceed with wetland construction should be made after considering the technical, regulatory, and economic factors, as well as long-term plans for vegetation maintenance and vector control.

Regardless of how a manager attains responsibility for stewardship of a wetland—building a wetland, assuming responsibility for an existing wetland, participating in a program to enhance wetland habitat, or assuming ownership of a shared wetland or land containing a wetland—as long as the wetland contains water, managers are legally responsible under the California Health and Safety Code for the costs of mosquito control or abatement of a public nuisance created by other organisms associated with that wetland.

Managing Mosquitoes in Surface-Flow Constructed Treatment Wetlands, ANR Publication 8117 William E. Walton, Department of Entomology, University of California, Riverside

Copyright © 2004 The Regents of the University of California, Division of Agriculture and Natural Resources. All rights reserved.