1st detected in mosquito pool in Imperial Valley, July 200

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Wetlands Restoration and Mosquito Management

• Sabrina Drill
• UC Cooperative Extension
• Los Angeles and Ventura Counties
• Sldrill_at_ucdavis.edu
• 323-260-3404

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Why Restore Wetlands?

• Wetland loss reduces environmental health.
  Wetlands are the sponges, kidneys, and
  supermarkets of the natural landscape. As
  sponges, they provide natural flood protectionAs
  kidneys, they filter sediments, nutrients, and
  contaminants from inflowing watersAs
  supermarkets, they provide the foods for a wide
  variety of local and migratory animals.Zedler,
  in Meffe and Carroll, 1994

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Why Mosquitoes?

• If you produce mosquitoes on your property, you
  can be held financially liable
• Mosquitoes can spread diseases among humans and
  other animals by acting as vectors
• Viral vector-borne diseases spread by mosquitoes
  are also known arboviruses (arthropod-borne
  viruses
• Malaria
• Several kinds of encephalitis
• West Nile Virus

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WNV in North America

• Human and equine outbreaks in Africa and Eurasia
  since 1930s
• First appeared in the U.S. in 1999 in New York
• NY strain unusual in
• Speed of spread
• Pathogenicity
• Rate of neuroinvasive disease
• Broad host range
• 2004 spread to 47 states, Puerto Rico, No. and
  Central America
• 9862 human cases, 264 deaths in US

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WNV in California

• 1st detected in mosquito pool in Imperial Valley,
  July 2003
• In 2004, found throughout state, most activity in
  southern California
• 1136 positive pools
• 3232 dead birds
• 830 human cases , 25 fatalities

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WNV in Wildlife

• Evidence of infection of 328 bird, 33 mammal, and
  2 reptile sps. in N. America
• 84 SoCal resident species, 66 migrants
• Infection and mortality rates vary
• Corvids have very high mortality
• Owls, raptors, several other songbirds species
• May lead to extirpation of Greater sage grouse
• Others, like American Coot and pigeons, do not
  develop viral loads or illness

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Species reported in DHS dead bird data 2004
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WNV in California 2005

• 45 counties
• 31 human cases, 2 deaths
• 619 positive birds in state lab so far
• Most from Central Valley and Southern California
• Orange, Riverside, San Bernardino
• Only 2 from San Diego

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Wetlands Restoration and WNV

• If restoration leads to aquatic habitat
  existing where it did not before, could increase
  mosquito production
• In most cases, restoration means improving the
  ecological function of existing wetlands. This
  reduces mosquito production.

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Mosquito biology

• 53 species in CA, at least 12 could vector WNV
• Eggs laid in or near water
• Differ in
• Way they lay eggs
• Length of larval stage
• Preferred prey
• Time of day of activity
• Ability to transmit disease
• Larvae breathe air through a tube
• Prefer slow, shallow water

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Implications for Mosquito management

• Constructed wetlands
• Inherently nutrient rich water favors mosquito
  production
• Designed to attract birds, provide needed habitat
  but increase avian disease risk
• Can be carefully manipulated/managed
• Natural or restored wetlands
• May function well, control mosquitoes
  ecologically, monitoring required
• May be in very poor condition, great mosquito
  habitat, really need restoration

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Treatment Wetlands

• High nutrients, low flow, may or may not include
  a habitat component

Prado wetlands, Orange County Water District
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Coastal Saltmarsh

• Higher, but variable, salinity changing water
  levels

Pt. Mugu, Sean Anderson
Malibu Lagoon, Cathy Jacobs
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Perennial Freshwater Wetlands

• May have seasonally inundated areas

San Joaquin Freshwater Marsh, UCI
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Riparian Ecosystems

• Moderate to high flow, may have seasonally
  inundated areas in floodplain

Santa Clara River, FSCR
Malibu Creek, S. Drill
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Vernal Pools

• Seasonally inundated, drying may
• result in deep soil fissures

Vernal Pool NWR in San Diego, USFWS
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Approaches to Mosquito Control in Wetlands

• It is far more effective to control breeding and
  larvae than adults
• Ecological management
• Water flow, depth, period of inundation
• Vegetation management
• Biological control
• Natural or introduced predators
• Larval or adult
• Chemical control
• Synthetic or natural origin

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Ecological Management

• Seeks to eliminate mosquito habitat
• Improve water quality elements
• Hydrologic elements
• Keep water flowing, aerated
• Keep retention time under 72 hours
• Maintain depth, keep slopes steep
• Vegetation Management
• Reduce dense stands of vegetation

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Ecological Management

• Management of both hydrodynamics and vegetation
  may run counter to intended wetland functions for
  water quality improvement and habitat

Source Metzger et al., 2002
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Biological Control

• Increase predation by natural or introduced
  predators
• Pros
• May be self-sustaining
• Reduce use of chemicals
• Native species might be used research ongoing
• Cons
• Usually, involves introduction of non-natives
• Can compete with or predate on native, non-target
  species

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Chemical Control

• Bacterial larvicides
• Effective and safe but expensive
• Chemical larvicides
• Surface oils or films suffocate larvae
• Toxicology to wildlife not well known
• Growth regulators inhibit development of larvae
• Toxicology to humans and wildlife very low
• Adulticides
• Most have higher toxicity to wildlife
• Pros
• Allows for very rapid specific treatment in area
  and time
• Cons
• Can harm fish, wildlife species
• Requires repeated application

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Cultural Management

• Reduce conflict with human population centers
• Appropriate site selection
• Buffer zones
• Establish guidelines for acceptable levels of
  nuisance vs. risk
• Restore watershed to re-establish natural
  hydrology, ecology, reduce mosquito production
• Cons
• May be impossible (cant re-plan the civic
  environment)
• Pros
• Reduces need for costlier control down the road

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Integrated Vector Management

• Develop monitoring plan to determine sources of
  mosquitoes
• Modify sources to reduce mosquito breeding
• Maintain equipment/infrastructure to function
  properly
• Monitor mosquito production
• Use minimum necessary response
• Control larvae when necessary
• Monitor to check effectiveness of control

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Factors in Designing IVM for Restored Wetlands

• Mosquito species and habitat
• Goals for wetland
• If nutrient reduction, may need to practice
  ecological and biological control EVEN IF it
  reduces habitat quality
• For habitat wetland, spot chemical control may
  have least impact
• Establish long term management and funding
  mechanism
• 5 year restoration grants not sufficient
• On-going monitoring and management necessary
• Coordinate with vector control
• Allow access for control activities
• Develop plan for on-going maintenance
• Coordinate with neighboring communities

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For more information about wetlands and
mosquitoes

• General information about Mosquitoes and West
  Nile
• http//celosangeles.ucdavis.edu/natural_resources/
  West-Nile-Virus.pdf
• Vector management
• Guides from UC DANR Press
• Managing Mosquitoes in Surface Flow Constructed
  Treatment Wetlands by Willam Walton, UCR, can be
  downloaded at http//anrcatalog.ucdavis.edu/mercha
  nt.ihtml?pid5595step4
• Managing Mosquitoes in Stormwater Treatment
  Devices by Marco Metzger, CA DHS, can be
  downloaded at http//anrcatalog.ucdavis.edu/mercha
  nt.ihtml?pid5601step4
•  
• Guides for vector control in wetlands around
  California
• Guidelines for Ecological Control of Mosquitoes
  on Non-Tidal Wetlands of the San Francisco Bay
  Area. Collins, Joshua N., and Resh, Vincent.
  1989. Mosquito and Vector Control Association of
  California, www.mvcac.org. Other publications of
  interested can be identified at the San Francisco
  Estuary Institute web site at http//www.sfei.org/
  staff_pubs/JCpubs2000.html
• Best Management Practices for Mosquitoes on
  Managed Wetland Environments (focusing on the
  Central Valley) should be available soon from the
  Central Valley Habitat Joint Venture,
  http//www.usbr.gov/mp/cvhjv/
• Information on controlling mosquitoes with
  minimal use of pesticides can be found at the
  website of the Northwest Coalition for
  Alternatives to Pesticides at http//www.pesticide
  .org/factsheets.html

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For more information about wetlands and mosquitoes

• Information about WNV and Wildlife
• Potential Impacts of West Nile Virus on Wildlife
  in California can be downloaded at
  http//www.vetmed.ucdavis.edu/whc/pdfs/wnvreport.p
  df
• National information about WNV and wildlife can
  be found at the website for National Audubon,
  http//www.audubon.org/bird/wnv/
• National Wildlife Health Center at
  http//www.nwhc.usgs.gov/
• Data and data reporting
• Surveillance information about the spread of WNV
  can be found at the UC Davis Center for Vector
  Borne Diseases at http//vector.ucdavis.edu/arbo.h
  tml
• General West Nile information can be found at the
  state Dept. of Health Services web site at
  http//www.westnile.ca.gov/. You can also report
  a dead bird at this site, or call 1-877-WNV-BIRD
• UCR West Nile Data Collection http//www.westnile
  virus.ucr.edu/