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Bandon Marsh National Wildlife Refuge
Pacific Region
Mosquitoes

Contact Us
with inquiries or questions:

Megan Nagel
Public Affairs Officer
U.S. Fish and Wildlife Service - Pacific Region
911 NE 11th Ave Portland, Oregon 97232
Office: (503) 231-6123
Email: oregoncoast@fws.gov

Current Status

Status on 3/26/2014
The U.S. Fish and Wildlife Service issued a special use permit to Coos County Public Health to conduct mosquito monitoring activities on Bandon Marsh National Wildlife Refuge. The County has hired a person to conduct the monitoring which will begin in early April.

Status on 3/19/2014
Materials from the March 18, 2014 public meeting are available for download here (1.2 MB PDF).

Status on 3/11/2014
The U.S. Fish and Wildlife Service requests a public review and comment on the proposed Integrated Marsh Management Approach to control mosquitos at Bandon Marsh National Wildlife Refuge.  The public review and comment period begins on March 11, 2014 and ends on April 9, 2014.

**Download the draft Supplement Environmental Assessment for Tidal Marsh Restoration at Bandon Marsh Refuge (939 KB PDF) **

**Download the draft Environmental Assessment for Mosquito Control at Bandon Marsh Refuge (3,821 KB PDF)**

Status on 11/19/2013
An errata sheet documenting corrections to the November 2013 Environmental Assessment entitled "MetaLarv S-PT Treatment on the Ni-les'tun Unit of Bandon Marsh NWR" is available for download here (26 KB PDF).

Status on 11/8/2013
The post-treatment NEPA compliance documentation for the September 12, 2013 MetaLarv S-PT Treatment on the Ni-les'tun Unit of Bandon Marsh NWR is available for download here (3.7 MB PDF).

Status on 9/12/2013
A single-engine fixed wing aircraft applied MetaLarv S-PT at 4.0 lbs/acre to 292 acres of the Ni-les’tun Unit of the Refuge. The application was conducted under a contract between Coos County and Vector Disease Control International.

Status on 8/30/2013
Coos County Public Health officials and the U.S. Fish and Wildlife Service (USFWS), in consultation with refuge biologists and mosquito control experts, have developed an emergency short-term mosquito abatement plan for the Bandon Marsh National Wildlife Refuge. The Service will be providing funding for the application of a larvicide, which prevents larval mosquitoes from maturing into adults, and an adulticide, which targets flying, adult mosquitoes, to refuge lands to lessen the impacts to refuge visitors, the public and adjacent landowners. The recent explosion of mosquito numbers in and around the Bandon Marsh has resulted in an urgent need to implement measures that will control the current situation and mitigate future mosquito explosions. On August 24, Coos County Public Health issued a Health Advisory for excessive mosquito numbers and associated health impacts to residents. On August 26, USFWS Project Leader Roy Lowe declared an emergency on Bandon Marsh NWR, and issued a Special Use Permit to the Coos County Public Health Department for mosquito abatement on refuge lands. This Emergency Declaration and Special Use Permit allows application of select adulticide and larvicide on refuge lands. On August 30, Coos County Public Health issued a Draft “Proposal for Mosquito Control on the Bandon Marsh Refuge and Surrounding Area” and is actively seeking cost estimates from vector-control businesses to address the immediate mosquito problem this year. USFWS is working with experts to develop a long-term solution that includes an Integrated Marsh Management Plan that will incorporate mosquito control.

Frequently Asked Questions **Download as a PDF (40 KB)**

Why are there so many mosquitoes on Bandon Marsh National Wildlife Refuge?
Why are there so many mosquitoes on Bandon Marsh National Wildlife Refuge?
In 2011, Bandon Marsh National Wildlife Refuge completed the restoration of 420 acres of tidal marsh - the largest ever in Oregon. The restored Ni-les'tun tidal marsh is succeeding in increasing use by wildlife, including migratory waterfowl and shorebirds, along with native fish species, including the threatened coho salmon. However, an unanticipated by-product of the restoration was the large population increase of the salt marsh mosquito (Aedes dorsalis). Shallow pools resulting from the marsh restoration, which were inadvertently created as filled ditches subsided or in ruts left by equipment, provided new breeding habitat for these mosquitoes. Though mosquitoes were present in the area prior to marsh restoration, they had much less available habitat. No other salt marsh restoration effort in Oregon had experienced this issue before.

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What is the Service doing to control mosquitoes at Bandon Marsh NWR?
What is the Service doing to control mosquitoes at Bandon Marsh NWR?
The U.S. Fish and Wildlife Service is working closely with Coos County Public Health, the Coos County Commissioners, members of Congress, and experts in the field of mosquito control to develop an Integrated Marsh Management approach that will control mosquitoes in the long term by drastically reducing the amount of available breeding pools by improving tidal flow throughout the Ni-les'tun Unit, and until habitat reduction takes effect, by applying larvicides to control mosquito numbers. The Draft Supplemental Environmental Assessment for the Ni-les'tun Unit of the Bandon Marsh National Wildlife Refuge Restoration Project proposes to improve the tidal hydrology and productivity of the Ni-les'tun Unit for fish and wildlife. The larvicides that are proposed to be used in the Draft Plan and Environmental Assessment for Mosquito Control for the Bandon Marsh National Wildlife Refuge and the methods of their application were selected for their minimal negative effects on the environment and efficacy for mosquito control. With the conclusion of the planning process (anticipated for spring 2014), plan implementation would begin with intensive monitoring of mosquito development in order to be able to address significant hatches with larvicide application. The proposed work to reduce mosquito breeding habitat would take place this summer. Details about the Service's Integrated Marsh Management approach and draft plans for mosquito control are available for above.

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Are the mosquito species documented at Bandon Marsh vectors or carriers of disease?
Are the mosquito species documented at Bandon Marsh vectors or carriers of disease?
The dominant species of mosquito found at Bandon Marsh NWR is Aedes dorsalis or the salt marsh mosquito. Aedes mosquitoes have been documented as secondary vectors for California Encephalitis and are considered to be low to moderately efficient vectors for West Nile Virus. However, Aedes dorsalis is of most concern as an adverse health impact and a public health risk because they do occur in large numbers, bite throughout the day and cause severe allergic reactions in some people.

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Who is paying for mosquito control?
Who is paying for mosquito control?
The Service has committed to funding the restoration work necessary to reduce the amount of available mosquito habitat on the Ni-les'tun Unit of Bandon Marsh NWR by creating channels to improve tidal flows throughout the marsh. The Oregon Watershed Enhancement Board is also contributing funding toward the restoration work. Because there is currently no Mosquito Control District in Coos County, the Service is also providing funding to Coos County Public Health to monitor mosquitoes and control mosquitoes with the use of approved larvicides on the Refuge. The final cost of mosquito control will depend on the contractor hired by Coos County Public Health to carry out this work and the extent of the area that is treated; however, the Service can only fund mosquito control work that occurs on the Refuge.

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Why are pesticides being proposed for mosquito control on Bandon Marsh National Wildlife Refuge?
Why are pesticides being proposed for mosquito control on Bandon Marsh National Wildlife Refuge?
The Service has developed a comprehensive Integrated Marsh Management approach that will ultimately reduce both the amount of available mosquito habitat and the numbers of mosquitoes. This long term approach emphasizes modifying the restoration site hydrology to eliminate most of the mosquito breeding pools that were inadvertently created. However, the work needed to accomplish that cannot begin until summer 2014, and will therefore not be completed in time to prevent the expected large fly-offs of mosquitoes in spring and summer of 2014. Consequently, to manage mosquito numbers in the short-term the Service is proposing to use larvicides to kill mosquitoes in their aquatic immature life stages as they hatch in breeding pools on the Refuge, until the plans to eliminate mosquito-breeding habitat are implemented and begin to be effective.

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What kind of pesticides may be used to treat refuge land for mosquitoes?
What kind of pesticides may be used to treat refuge land for mosquitoes?
Pesticides that target immature mosquitoes are called larvicides and these are proposed for use. Pesticides that target adult mosquitoes are called adulticides. The Service is not considering the use of adulticides on Bandon Marsh NWR. Larvicide use is intended primarily as a supplement to, rather than substitute for, the physical marsh manipulation that will reduce the amount of available mosquito habitat on the Ni-les'tun Unit of Bandon Marsh National Wildlife Refuge.

Larvicides affect the four larval stages of mosquitoes known as instars. They can be applied through a wide variety of methods including hand application and backpack sprayers, amphibious tracked vehicle, truck-mounted equipment and aerial sprayers. Mosquito larvicides being considered by the Service include Bti, methoprene, and CocoBearTM. Much more information about these larvicides is available in the Draft Plan and Environmental Assessment for Mosquito Control on Bandon Marsh National Wildlife Refuge.
  • Bacillus thuringiensis (Bt) is a naturally derived soil bacterium that acts as a larval arthropod stomach poison. Several varieties of Bt have been discovered and identified by the specificity of the toxins to certain insect orders. Bacillus thuringiensis israelensis (Bti) is specific only to certain primitive dipterans (flies), particularly mosquitoes. Bti is the form proposed for use on the fresh or brackish water breeding sites at the Ni-les'tun Unit of the Bandon Marsh Refuge. Bti is not toxic to non-dipteran insects including bees, moths, and butterflies, or fish, mammals, and birds.

  • Methoprene is a synthetic mimic of a naturally produced insect hormone. When an insect is exposed to methoprene, a hormonal imbalance in the development of the insect results, and it dies before it can mature into an adult. For mosquito control, methoprene is applied directly to the larval breeding pools. It is available in several formulations including micro-encapsulated and extended-release formulations that remain effective for up to 42 days. Single-dose formulations released into water are non-persistent with a half-life of about 30–40 hours. Methoprene can affect other animals with exoskeletons, such as other aquatic insects, shrimp, and crabs, but the lower concentrations applied to kill mosquitoes are generally not harmful to these other animals, and most of them would only be exposed to methoprene that is greatly diluted by tidal waters.

  • CocoBearTM is a surface film that is applied to mosquito breeding sites to kill aquatic larvae and pupae. The product creates a barrier at the air-water interface and suffocates the insects, which require periodic contact with the water surface in order to breathe. CocoBearTM is 10% mineral oil and is effective for 2–3 days. Surface oils such as CocoBearTM are potentially lethal to any aquatic invertebrate that lives on the water surface or requires periodic contact with air to breathe. The use of this product would be very limited and would only be directly applied to pools containing large numbers of 4th instar larvae or pupae that may pose a health and safety threat, and were not effectively treated with other larvicides.

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What are the potential effects of the selected pesticides on people, water, pets, livestock, crops, and wildlife?
What are the potential effects of the selected pesticides on people, water, pets, livestock, crops, and wildlife?
The three larvicidal products included in the draft Mosquito Pesticide Plan were selected because, after intensive toxicological review, they were determined to be the least toxic options that would be effective at controlling the salt marsh mosquito in the refuge environment. They represent the "state of the science" of targeted pest control with minimal environmental effects, and are consistent with the Service's mission to conserve native wildlife, including threatened and endangered species. The proposed plan adopts methods of pesticide application that insures that minimal amounts of pesticide will be applied only as needed, and avoids exposure of non-target species whenever possible. The larvicides proposed were selected after thorough toxicological review concluded that they were the least toxic options that would be effective at mosquito control in the refuge environment, and have minimal effects on non-target species and marsh ecology. The Service has completed a Draft Plan and Environmental Assessment for Mosquito Control that comprehensively addresses the possible effects to human health, soil, air, water, plants, and wildlife, and how the Plan mitigates those effects. Download the plan above or request a hard copy by calling the U.S. Fish and Wildlife Service at 541-867-4550 or emailing at oregoncoast@fws.gov.

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When larvicides are planned for use on refuge lands, how and when will the public be notified?
When larvicides are planned for use on refuge lands, how and when will the public be notified?
The Service is collaborating with the Coos County Public Health Department to conduct education and outreach activities aimed at protecting human and wildlife health from threats associated with mosquitoes. Once approved and prior to implementing the plan that will include application of larvicide on the Ni-les'tun Unit of Bandon Marsh National Wildlife Refuge, notification will be made public on the Coos County Public Health's website at http://www.co.coos.or.us/Departments/PublicHealth/PublicServiceAnnouncements.aspx and notification will be sent to news outlets throughout Coos County. However, once the plan is implemented, larvicide application will depend on mosquito monitoring results showing that application is needed, and will occur immediately without public notification of each instance, unless aerial application is deemed necessary, for which the public will be notified in advance. All applications are expected to be of larvicides applied directly to mosquito breeding pools located on the Refuge, and will not affect adjacent lands or visitors to the Refuge.

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How will mosquito populations be monitored?
How will mosquito populations be monitored?
Monitoring of immature (larval and pupal) mosquitoes on the Refuge will be conducted by the Coos County Public Health and funded by the Service. County staff will develop and maintain a list and map of known mosquito breeding sites on the Refuge and visit them during likely periods of mosquito production. Mosquito populations would be sampled using established protocols and samples would be examined by Coos County Public Health to determine the abundance, species, and life-stage of mosquitoes. This information would be compared to database records and established thresholds and would be used as a tool for future treatment decisions.

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Will the Service also be using pesticides to treat private lands for mosquitoes?
Will the Service also be using pesticides to treat private lands for mosquitoes?
No. Please refer to the Coos County Public Health's website (http://www.co.coos.or.us/Departments/PublicHealth/PublicServiceAnnouncements.aspx) for information about mosquitoes and pesticide application outside of refuge lands. The Service has no authority over the County's mosquito control activities on other federal, state, county, and privately-owned lands.

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How do I comment on the proposed plan to control mosquitoes?
How do I comment on the proposed plan to control mosquitoes?
A Draft Plan and Environmental Assessment for Mosquito Control and a Draft Supplemental Environmental Assessment for Tidal Marsh Restoration for Bandon Marsh National Wildlife Refuge outlining these alternatives will be available for review and comment beginning March 11, 2014 and ending April 9, 2014. The Service invites the public to review the draft documents and encourages active participation. Printed copies can be requested from the Refuge Office at (541) 867-4550 or by emailing oregoncoast@fws.gov.

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News Releases

March 11, 2014: Draft Mosquito Management Plans for Bandon Marsh National Wildlife Refuge Available for Public Review and Comment

February 14, 2014: U.S. Fish and Wildlife Service is working with Coos County to develop a marsh and mosquito management plan

August 30, 2013: Coos County and U.S. Fish and Wildlife Service Mosquito Treatment Plan to Move Forward at Bandon Marsh

July 3, 2013: Bandon Marsh Refuge partners with experts in mosquito study

Timeline through August 30, 2013:

For more information on the timeline of events through the end of summer 2013, click here.

Pre tidal marsh restoration: Mosquitoes have always been present in the lower Coquille Estuary and Bullards Beach State Park areas but in unremarkable numbers.

Early Fall 2011: Bandon Marsh NWR’s Ni-les’tun Unit tidal marsh restoration project completed.  A natural tidal regime is re-established in the historic saltmarsh to assist estuary-dependent fish (salmon) and wildlife (migratory birds) for the benefit of the American public.

Summer 2012:
Refuge staff received several calls and one letter describing increased mosquito numbers from landowners across the river from the Ni-les’tun Unit.  Refuge Staff coordinated with Regional Office regarding USFWS mosquito management policies.  USFWS guidance generally limits mosquito surveillance and control activities on refuge lands to those conducted by local county Mosquito Abatement Districts through Special Use Permit.

Fall 2012:
Refuge staff began coordinating with Coos County Public Health concerning the complaints of increased mosquito numbers and investigated whether mosquito-transmitted disease was historically an issue with mosquitoes in Coos County.  Refuge staff began detailing funding needs for USFWS-led inventory and monitoring of mosquitoes, which are activities that are normally carried out by local Mosquito Abatement Districts on refuges across the country.

Winter 2012/2013:
USFWS began discussions of mosquito inventory and monitoring needs on the Refuge with Oregon Vector Control Organization and Private Vector Control Managers.  Discussions continued with Coos County Public Health concerning inventory and monitoring needs on Refuge lands.  USFWS coordinated with Oregon State University (OSU) Entomology and Zoology Departments concerning assistance in inventory and monitoring; however, there are no public health/vector control entomologists on staff.

Spring 2013:
USFWS coordinated with Center for Disease Control, Oregon State Health Department, U.S. Geologic Survey Research Branch, and Private Mosquito Research organizations concerning funding for inventory and monitoring. No funding was readily available.

May 2013:
Spring high tides (late May) flooded the upper most portions of the marsh on the Ni-les’tun Unit and created pooled shallow waters in depressions caused by subsiding filled agricultural ditches and ruts from equipment used during the restoration effort. Discussions continued with OSU Entomology Program for assistance, and Refuge staff established a working relationship with OSU.

June 5–15, 2013:
The first major adult mosquito emergence occurred 10–15 days after the high tide of May 26; Refuge staff received the first complaints from adjacent landowners about large numbers of mosquitoes.

June 27–28, 2013:
OSU/USFWS began sampling of adult and larval mosquitoes on Bandon Marsh NWR for species identification. This was coordinated with Multnomah and Benton County Public Health/Vector control programs due to the lack of a local Mosquito Abatement/Vector Control District in Coos County. 

July 11–12, 2013: OSU sampled for adult and larval mosquitoes on Ni-les’tun Unit.  Larvae numbers were low in most areas on the Ni-les’tun Unit.  Pools had dried up from sun and summer winds, and the numbers of adults were observed to be decreasing. Mosquito samples were sent in to experts for identification. The reason for the need to identify mosquito species is that each species requires different habitat conditions to proliferate and expand, and without a clear understanding of the species present, it would not be possible to take effective action to reduce mosquito breeding habitat and thus mosquito numbers.

Week of July 21, 2013:
Multnomah County Public Health Department – Vector Control identified the adult and larval mosquito samples collected on July 11/12.  Five species were identified including Culex tarsalis, Culex pipiens, Aedes cinereus and Culisetas particeps.  They indicated that by far the most abundant species was Aedes dorsalis, commonly known as the salt marsh mosquito.  This species breeds primarily in brackish and saline habitats and under the right conditions breeds in abundance in intertidal marshes.  The majority of females live less than 90 days and males rarely live for more than 30 days.  This species can fly long distance (reportedly up to 30 miles, which is probably wind aided), and is a vicious biter night and day.  Populations left unchecked grow with each generation and under ideal conditions they can produce 8 generation/year. 

July 25–26, 2013:
OSU/USFWS sampling followed the recent high tide series.  Researchers reported finding larvae in great abundance in nearly every shallow ponded depression they encountered.  In one location they had 300–400 larvae in a single dip.  Another large flyoff of adult mosquitoes was expected this week or next. 

Week of August 4, 2013:
Refuge acquired a small moldboard plow to be pulled by a 6-wheel Amphibious ATV in the hopes of connecting some of the low areas to tidal channels to increase water circulation. Refuge staff began to plow small ditches to drain small ponds holding water and determined that the tool had very limited effectiveness on a large scale.  The determination was made that a much bigger effort was needed, including engineering, design and use of large equipment.

August 8–9, 2013:
OSU continued sampling of adults and larvae. Numbers of mosquito larvae and adults were observed to be decreasing slightly. A formal Cooperative Agreement with OSU Entomology Program was established to continue mosquito work including identifying species and breeding areas.

August 16, 2013:
Bandon Marsh Refuge Manager David Ledig met with Dr. Nikki Zogg, Administrator for Coos County Public Health, at the Bandon Marsh Office.  Manager Ledig gave Dr. Zogg the history of refuge coordination with the Coos County Health Department over the last year and a half, to ensure that she was aware of USFWS efforts to coordinate with Coos County and to explain how Multnomah County Public Health Department got involved through our work with OSU. He provided her with a list of mosquito species we have documented, that led to a discussion about our restoration effort, the effects of tidal flooding on A. dorsalis, the NWR mosquito Integrated Pest Management policy/process, and USFWS’ current plans to conduct mosquito breeding site reduction through habitat management. 

August 19, 2013:
City of Bandon passed Resolution 13-21:  Demanding Federal Government Action to Abate the Mosquito Problem Caused by the United States Fish & Wildlife Service Development of the Ni-les’tun Unit of the Bandon Marsh National Wildlife Refuge.

August 20, 2013:
Project Leader Roy Lowe attended a Town Hall with Senator Merkley and provided information on the current mosquito situation at Bandon Marsh and the efforts to remedy a solution to the problem.

August 22, 2013:
Dr. Nikki Zogg of Coos County Public Health issued a Health Advisory for excessive mosquito numbers and associated health impacts to residents.

August 22, 2013:
Refuge and regional staff discussed potential treatment prescriptions to control the mosquito source population for the remainder of this mosquito season.  Participants in the discussion included managers and vector control biologists from other National Wildlife Refuges and Mosquito Vector Control Districts, and technical representatives from mosquito treatment providers that are familiar with salt marsh mosquitoes.

August 22–23, 2013:
Oregon State University continued sampling of adults and larvae.  All five documented species were found in the adult traps and larvae were observed in approximately 50% of the depressions with pooled water.

August 23, 2013:
Jackson County Vector Control District (VCD) was contacted by Coos County Public Health about the mosquito situation at Bandon Marsh because Coos County has no vector control district.  Based upon a recent request from the City of Bandon and Coos County, Jackson County VCD provided a proposed mosquito control prescription for Bandon Marsh based upon limited information about the mosquito problem; the prescription involved both a larvicide and adulticide treatments.

August 26, 2013:
USFWS Project Leader Roy Lowe declared an emergency on Bandon Marsh NWR due to excessive numbers of mosquitoes, and issued a Special Use Permit (SUP) to the Coos County Public Health Department for mosquito abatement on refuge lands.  This SUP allows Coos County to apply select adulticide and larvicide treatments on refuge lands.

August 27, 2013:
USFWS Deputy Regional Director Richard Hannan and Public Affairs Officer Megan Nagel of External Affairs attended the Coos County Commissioners meeting in Coquille to answer questions from County Commissioners and the public about the mosquito issue on Bandon Marsh NWR.

August 29, 2013:
Project Leader Roy Lowe participated in a live interview on OPB’s Think Out Loud, with Mary Schamehorn (Mayor, City of Bandon). 

August 29, 2013:
Refuge and Regional staff met at Bandon Marsh NWR with the mosquito control experts and Dr. Nikki Zogg of Coos County public health Department to discuss and assist Coos County in the proposed immediate abatement treatment on the Refuge.    Coos County also discussed with the experts their proposed plans to treat off-refuge areas in the vicinity of the refuge.

August 30, 2013:
The Coos County Public Health Department released a Draft “Proposal for Mosquito Control on the Bandon Marsh Refuge and Surrounding Area”.  The purpose of this plan is to inform the County Commissioners, USFWS, and the public concerning implementation measures that will aid in the control of the current mosquito situation and help reduce future mosquito explosions. Coos County commissioners will consider the plan for approval next week. USFWS is funding the control effort, and Coos County Public Health is seeking cost estimates from vector-control businesses to address the existing mosquito problem.  USFWS is working to develop a long-term solution that includes an Integrated Marsh Management Plan that will incorporate mosquito control.  Coos County Public Health Department and USFWS also issued a joint news release today to update the public on the situation.

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