Handbook for Mosquito Management on National Wildlife Refuges - June 2018 - U.S. Fish & Wildlife Service
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U.S. Fish & Wildlife Service Handbook for Mosquito Management on National Wildlife Refuges June 2018
“The mission of the National Wildlife Refuge System is to administer a national network of lands and waters for the conservation, management, and where appropriate, restoration of the fsh, wildlife, and plant resources and their habitats within the United States for the beneft of present and future generations of Americans.” National Wildlife Refuge System Improvement Act of 1997 Photo credit: Don Brubaker, USFWS, 2011 Joy Albertson, Supervisory Wildlife Biologist, San Francisco Bay NWRC, and Jason Sequeira, Field Supervisor, Marin/ Sonoma Mosquito Control, and Vector District, CA dipping for mosquito larvae at San Pablo Bay National Wildlife Refuge.
U.S. Fish & Wildlife Service
Handbook for Mosquito Management
on National Wildlife Refuges
Introduction ............................................................................................................................................................ 1
Purpose and Scope of the Handbook...................................................................................................................... 2
Principles of Integrated Pest Management.......................................................................................................... 4
Mosquito Management Plan.................................................................................................................................. 5
Statement of Purpose and Need .............................................................................................................. 6
Refuge Natural Resources (including maps) .......................................................................................... 6
Mosquito Ecology and Life History ......................................................................................................... 6
Climate Change ........................................................................................................................................... 7
Health Considerations ................................................................................................................................ 7
Mosquito-Borne Disease ...................................................................................................................... 8
Mosquito Related Human Health Considerations ........................................................................... 8
Animal Health Considerations ............................................................................................................ 8
Mosquito-Vectored Pathogen Surveillance and Mosquito Monitoring ................................................. 8
Mosquito Management Options .............................................................................................................. 11
Best Management Practices ............................................................................................................. 11
Managing Habitats for Mosquito Source Reduction ..................................................................... 11
Mosquito Control ................................................................................................................................ 12
Larvicides, Pupacides, Adulticides .................................................................................................. 16
Modifed Mosquitoes ............................................................................................................. 17
Thresholds for Action - Risk Management ............................................................................................ 18
Pesticide Treatment Decisions ............................................................................................ 19
Human Health Emergencies ................................................................................................ 21
Natural Resource and Compliance Monitoring and Reporting .......................................................... 21
Natural Resources Monitoring ........................................................................................ 21
Mosquito Management Implementation Compliance Monitoring................................... 21
Reporting ............................................................................................................................... 22
Adaptive Management .............................................................................................................................. 22
Education and Outreach ........................................................................................................................... 22
Local Mosquito Situation and Communication .................................................................... 22
Prevention ............................................................................................................................... 23
Natural Mosquito Predators ................................................................................................ 24
Glossary ............................................................................................................................................................... 25
Literature Cited and General References.............................................................................................................. 27
Appendices ......................................................................................................................................................... 30
Appendix A Authorities and Policies Relevant to Mosquito Management .............................. 30
Appendix B Summaries of Common Mosquito-Borne Diseases in the United States and
Other Mosquito-Related Human Health Considerations..................................... 35
Appendix C Action Threshold - Example ..................................................................................... 39
Appendix D Animal Health Considerations ................................................................................ 44
Handbook for Mosquito Management on National Wildlife Refuges iii Handbook for Mosquito Management on National Wildlife Refuges
Introduction
The U.S. Fish and Wildlife Service (Service) Unless mosquitoes interfere with refuge-specifc
considers native mosquitoes a part of the natural management goals and objectives, or cause a
ecosystem in the National Wildlife Refuge System public or wildlife health risk, they are allowed to
(Refuge System) habitats in which they occur. exist unimpeded on a refuge. Mosquito-vectored
The Service allows mosquitoes on refuges to exist pathogens that cause disease are the primary public
unimpeded unless they pose a specifc human or health concern associated with mosquitoes on a
wildlife health risk. Sometimes Refuge Managers refuge. When faced with mosquito management
are called upon to manage mosquitoes on-refuge in decisions affecting Refuge System lands and waters,
coordination with local public health or mosquito the Service’s position is to work with public health
control organizations. This handbook applies to agencies and/or mosquito control organizations
mosquito management activities related to reducing using the most effective method or combination of
risks to public health from mosquito-borne disease. methods that pose the lowest risk to fsh, wildlife,
and their habitats. Often, the Service’s preferred
A Refuge Manager may authorize others to conduct mosquito management option is to use non-pesticide
mosquito management activities on a refuge to based tools.
protect public health when local, current mosquito
monitoring data provided by the public health Under Service policy, integrated pest management
agency or an authorized designated representative (IPM) is a sustainable approach to managing
indicate that mosquitoes on the refuge are causing, pests by combining physical, biological, cultural,
or are expected to cause, a public health threat. and chemical tools in a way that minimizes health,
Mosquito management includes the following environmental and economic risk. Effective
activities: planning, identifcation and inventory mosquito management on refuges requires planning
of mosquito species, surveillance and monitoring, that follows the IPM principles. This handbook for
establishing action thresholds, prevention, control mosquito management is a stepdown handbook for
(to suppress and/or reduce mosquitoes), restoration, the Service IPM policy (569 FW 1).
research, and outreach and education activities
used to minimize risks to public health. All Refuge
System mosquito management activities, including
Service planning documents, must be consistent
with all applicable Federal laws, regulations and
policies.
Handbook for Mosquito Management on National Wildlife Refuges 1Purpose and Scope of this Handbook
This handbook establishes the Service’s The Service relies on public health authorities
interpretation of existing laws, regulations, and mosquito control organizations to determine
and policies that allow us to authorize mosquito the risks and threats to public health related to
management activities on Refuge System lands mosquito-borne pathogens and to advise us on
and waters. The handbook provides consistency in management actions to minimize these risks. Public
the decision-making process regarding mosquito health authorities may work with refuge staff to
management on national wildlife refuges for implement integrated pest management principles
protection of public health. In general, the Service that include the following:
does not treat for mosquito-vectored wildlife
disease. The handbook guides development of (1) Identifying mosquito species in the area
Mosquito Management Plans (MMP) in compliance and understanding their life history and
with the National Environmental Policy Act and conditions that support their production;
provides information to make informed management (2) Monitoring mosquitoes and mosquito-
decisions and minimize the impacts to natural borne pathogen surveillance (as needed)
resources from mosquito management activities on to provide relevant information to
Refuge System lands and waters. Mosquito control refuge staff;
activities may include prevention practices, habitat
management actions, biological controls, chemical (3) Establishing action thresholds that help
treatments, and, potentially, modifed mosquitoes. the Refuge Managers make informed
Mosquito management planning is most effective decisions about actions such as pesticide
when conducted in partnership with public health treatments, when needed;
authorities or their authorized representatives. (4) Recording decisions and effectiveness
Such representatives are often mosquito control of actions implemented; and
or mosquito abatement districts (referred to (5) Monitoring for effcacy, compliance,
throughout the handbook as “mosquito control and non-target impacts.
organizations”).
Mosquito management planning for a national
Mosquito management planning includes identifying wildlife refuge must consider public health while
acceptable control strategies. An MMP serves as an protecting natural resources. Pesticides used to
important tool to communicate with the community manage mosquitoes have the potential to adversely
and provides common understanding of acceptable impact non-target species either directly or
and permitted mosquito management strategies indirectly. Some mosquito control pesticides impact
among the health authority, mosquito control the immune, reproductive, or nervous system of
organization, and the refuge staff. insects. Some larvicides kill susceptible chironomid
(midge) larvae, with research suggesting that
Planning is necessary to ensure that mosquito population-level impacts may affect the food web at
management activities on a refuge are compatible the community-level. Mosquito adulticide products
with the establishing purposes of the refuge. are broad-spectrum insecticides that may impact a
Mosquitoes are a part of the ecosystem; they wide variety of invertebrates and vertebrates.
serve as a food resource for other organisms.
Nevertheless, they are also pathogen vectors. The degree to which mosquito control pesticides
Generally, the Service receives no appropriated may impact non-target organisms or non-target
funds to conduct mosquito management activities insect communities is often diffcult to predict
and implementation of monitoring and treatment on- because of differences in sensitivity among species,
refuge is conducted by public health or the mosquito differences in toxicity of various formulated
management organizations. Mosquito management products, and basic knowledge gaps in species-
activities on refuges are considered a use of a specifc toxicity. There are few studies that examine
refuge and require a Special Use Permit (SUP). the non-target impacts of mosquito control
2 Handbook for Mosquito Management on National Wildlife Refugespesticides at diverse spatial and temporal scales. This handbook guides Service review, planning,
The use of mosquito larvicides is considered and authorization processes for use of lawfully
preferable to mosquito adulticides for several registered pesticides for mosquito control on-
reasons: refuge. The U.S. Environmental Protection Agency
(USEPA) assesses human health and non-target
(1) Larvicides prevent the emergence resource risks of pesticides during the pesticide
of adults; registration process. There is increasing attention
(2) Larvicides can provide up to a month to mosquito species evolving resistance to mosquito
(or longer) of control, rather than the pesticide products currently in use. Uncertainty
few hours provided by adulticides; about human health risks of pesticides, non-target
resources impacts, and resistance is ever changing;
(3) Most larvicides are far less toxic than that is why, in part, that the USEPA conducts
adulticides; and pesticide re-registration reviews. These concerns
(4) Larvicides are generally applied to support an integrated approach to mosquito
smaller spatial areas, thus impacting management.
fewer non-target resources.
This handbook is applicable to all units of the
For these reasons and in view of the mission of Refuge System where the Service has jurisdiction
the Refuge System, when mosquito management over mosquito management activities, regardless of
actions include pesticide use, they should target whether the Service or a Service-authorized entity
the mosquito larval stage. Mosquito larvicides / conducts the mosquito management actions.
pupacides pose less risk than adulticide products
to non-target species and the environment.
Handbook for Mosquito Management on National Wildlife Refuges 3Principles of Integrated
Pest Management (IPM)
Integrated Pest Management is a sustainable environmental risk. These IPM principles are the
approach to managing pests by combining foundation for mosquito management planning and
physical, biological, cultural, and chemical tools implementation.
in a way that minimizes economic, health, and
The Principles of Integrated Pest Management
• Understand the refuge management
objectives and establish short- and long-term
priorities. Refuge objectives would be found in the • Build partnerships and consensus with
Comprehensive Conservation Plan (CCP) or in the stakeholders, such as communities and decision-
Habitat Management Plan, or both. Decide on your makers. Example: Public health agency staff
refuge objectives for mosquito management; use and technical experts such as mosquito control
specifc, measurable, achievable, realistic, and time- organization staff. Partnership building is an on-
based objectives when choosing tools. Example: going effort throughout the process.
Due to past history of mosquito-vectored disease
in the area, a Refuge Manager may allow a public • Review available tools and BMPs for mosquito
health district or a mosquito control organization to management. Tools and strategies can include: 1)
treat some mosquito breeding habitat on the refuge no action, 2) physical (manual and mechanical), 3)
for larval mosquitoes if the public health district cultural, 4) biological, and 5) chemicals.
requests it. • Establish the “action threshold” at which
• Prevent mosquitoes from becoming a pest at a management action will be implemented to
your site. This is the frst line of defense against any control the pest population. (Action thresholds are
pest species. See the Best Management Practices a key Mosquito Management Plan (MMP) element
(BMPs ) section of the handbook. and are discussed in detail later in the handbook.)
• Identify and monitor the pest species • Obtain approval, defne responsibilities, and
(mosquito), and know the life history, and the implement preventive and best management
conditions that support the pest(s). Similarly, practices (BMPs) and control treatments, in
know the diseases that are vectored by the accordance with applicable laws, regulations,
mosquitoes that occur in your area. The Centers policies and the refuge MMP.
for Disease Control and Prevention (CDC), • Practice adaptive management. Evaluate
public health agencies, and mosquito control results of implemented management strategies
organizations have relevant information. Access through authorized monitoring; determine
information on the CDC website located at https:// if objectives have been achieved, and modify
www.cdc.gov/niosh/topics/outdoor/mosquito-borne/ strategies, if necessary.
• Understand the physical (air, water, food, • Maintain written records. Document decisions
shelter, temperature, and light) and biological and report treatments implemented and monitoring
factors that affect the number and distribution results.
of mosquitoes and any natural enemies. Conserve
natural enemies when implementing any strategy. • Outreach and education. Inform refuge staff
Integrated marsh management, for example, can of the mosquito management issues in and around
restore high marsh pools to serve as native fsh the refuge, and prepare informative materials for
reservoirs in areas that had been previously drained. outreach to visitors.
4 Handbook for Mosquito Management on National Wildlife RefugesMosquito Management Plan
If mosquito management activities occur on or the local public health authorities and mosquito
impact a refuge, then refuge staff should prepare control organizations. Regardless of refuge-specifc
an MMP. An MMP is a step-down management plan circumstances, collaborating with experts who
with specifc objectives and strategies that support work for local public health authorities or mosquito
the objectives identifed in a CCP. An MMP is control organizations will help refuge staff plan
also identifed as an integrated pest management for mosquito management. Planning also provides
plan. Mosquito management planning provides transparency of operations and public inclusion
the Service with the opportunity to assess the in decision-making. The MMP may include the
impacts of mosquito management activities and following sections where appropriate, recognizing
helps to ensure the protection of natural resources. the need for refuge-specifc fexibility in planning.
Mosquito management planning facilitates the
development of the working relationships with
National Wildlife Refuge Mosquito Management Plan
Statement of Purpose and Need
Refuge Natural Resources (including maps)
Mosquito Ecology, Life History, and Pathogen Transmission
Climate Change Infuences
Health Considerations - Human and Animal
Mosquito-vectored Pathogen Surveillance and Mosquito Monitoring
Mosquito Management Options
Best Management Practices
Managing Habitats for Mosquito Source Reduction
Mosquito Control Products
Larvicides, Pupacides, Adulticides
Modifed Mosquitoes
Thresholds for Action - Risk Management
Pesticide Treatment Decisions
Human Health Emergencies
Natural Resource and Compliance Monitoring and Reporting
Natural Resources Monitoring
Mosquito Management Implementation Compliance Monitoring
Reporting
Adaptive Management
Education and Outreach
Local Mosquito Situation and Communication
Prevention
Natural Mosquito Predators
Handbook for Mosquito Management on National Wildlife Refuges 5I. Statement of Purpose and Need • Structures, components, and functions of
the ecosystem(s) of which the refuge is a part;
State the purpose of the refuge MMP • Rare or declining fsh, wildlife, and plants and
and clearly articulate the public health their habitats and communities; and
∑ need for mosquito management on the
refuge. • Special management areas (e.g., wild, scenic,
and recreational river areas; wilderness
areas).
Relate the need for mosquito management planning
to refuge goals and objectives, as appropriate. For III. Mosquito Ecology, Life History,
example, if the refuge provides habitat for a federally
listed butterfy, then mosquito management planning and Pathogen Transmission
might be crucial to minimize impacts to the species and
its habitat while conducting mosquito management Summarize the inventory of mosquito
control activities.
∑ species on refuge and their potential as
pathogen vectors.
II. Refuge Natural Resources
This handbook focuses on mosquito management
Summarize the natural resources and planning and decision-making as required for the
∑ potential impacts from mosquito
management.
purposes of protecting public health from diseases
caused by mosquito-vectored pathogens regardless of
whether vectored by a native or non-native mosquito
species. Over 80 million years and the evolution
A thorough review of the natural resources and the of 3,500 mosquito species, there are now over 175
impacts of the mosquito management actions, such species of native and non-native mosquitoes in the
as habitat manipulation or effects of pesticides on contiguous United States. Not all mosquito species
the natural resources, is necessary. Natural resource are vectors of disease. Mosquitoes vary in pathogen
descriptions are often presented in an Environmental transmission effciency, habitat and host requirements,
Assessment as part of National Environmental Policy and, therefore, they may require different control
Act (NEPA) compliance; however, if natural resources strategies. Many native mosquito species are prey for
have been addressed within another NEPA-compliant other aquatic and terrestrial fauna and because of their
planning process, such as in a CCP, then you can role in ecosystems, thorough planning is necessary to
incorporate that review by reference. minimize impacts when mosquito management actions
are implemented on refuge to protect public health.
As a publicly vetted document, appropriate CCP
chapter(s) on natural resources can be copied or Inventory and identifcation of the mosquito species
cited into the Natural Resources section of the MMP. that reproduce on the refuge is fundamental
Potential content may include, but is not limited to: information in mosquito management planning. In the
MMP, include an inventory of the mosquito species
• Distribution and abundance of fsh, wildlife, known or suspected to occur on and near the refuge
and plant populations, including any and brief life histories. Species that may vector disease
threatened or endangered species and pathogens are particularly important to include. This
related habitats; handbook does not provide life histories because they
are readily available online. Sources for determining
• Wildlife habitat and species’ relationships species of mosquitoes currently occurring on or near
that may be impacted by mosquito a refuge are usually available on websites of the local
management; mosquito control organizations, and from the State and
local public health authorities. If there is no current
• Ability of the refuge to meet the habitat inventory of the mosquitoes species that occur on or
needs of fsh, wildlife, and plants; near the refuge, contact the local mosquito control
organization or public health agency to conduct an
• Context of the refuge in relation to the inventory. This is not a refuge function. A current
surrounding ecosystem; mosquito inventory is necessary because the species
6 Handbook for Mosquito Management on National Wildlife Refugesoccurrence may change with climate change or other decades, the effects of climate change have become
introductions, such as global transport. more measurable in coastal wetlands. Signs of
climate change include increased sea levels, marsh
In the aquatic environment, mosquitoes are most edge erosion from intense storms, and conversion
effectively managed in the larval and pupal life- of vegetated salt marshes to open water. Wherever
cycle stages (Figure 1) https://www.cdc.gov/Dengue/ there is increased standing water, mosquitoes are
entomologyEcology/m_lifecycle.html. more likely to occur. Managers must continue to
adapt strategies to the changing landscape and
consider mosquito production in management and
also periodically update the mosquito inventory on
the refuge.
Some scientists have reported that higher global
temperatures will enhance transmission rates of
mosquito-borne diseases (Shope 1991). Others
suggest that the geographic range of diseases will
change (Hales et al. 2002). Gubler et al. (2001)
reviewed the response of vector-borne pathogens to
climate changes and suggested that climate changes
will likely affect transmission patterns - some may
increase and some may decrease - and that we need
to understand more about how pathogens persist
It takes a mosquito between 4 to 30 days to develop and what conditions trigger amplifcation before the
from an egg to an adult, depending on species and role of the weather and long-term climate trends
water temperature. Mosquito larvae develop through can be determined. Reiter (2001) argued that
four instars. Skilled observers can determine the the histories of malaria, yellow fever, and dengue
instar of larvae and infer hatching or adult emergence suggest that human activities and their impact on
time. Instar information is critical for proper timing local ecology have generally been more signifcant
of larvicide or pupacide applications for maximum determinants of disease prevalence than climate.
effectiveness to help avert the need to use mosquito Since climate change scenarios differ across the
adulticides. Mosquito control organization staff are country and depend highly on local conditions,
usually skilled in mosquito life stage identifcation; refuge staff should consult local models as they
we do not expect the refuge staff to conduct this develop their mosquito management strategies.
identifcation.
V. Health Considerations
IV. Climate Change Infuences
Briefy identify and describe the
Provide a summary of how climate ∑ health considerations that drive the
∑ change could infuence mosquito MMP on the refuge.
production and habitats on your refuge.
Mosquito-vectored pathogens that cause disease
Changing environments, whether naturally are the primary public health concern associated
or through actions taken to restore habitats, with mosquitoes. Health considerations related
may result in increased or decreased mosquito to mosquitoes vary depending on the species
production. Climate change effects may include present, abundance, geographic area, and time
increased rainfall that creates ponded water, or of year. For most refuges and the surrounding
decreased precipitation and drought conditions communities, public health authorities and their
that reduce mosquito habitats (IPCC 2013). Sea authorized, designated representatives, such as
level rise may alter a landscape so that areas where a mosquito control organization, are responsible
mosquitoes have never been an issue eventually for surveillance of mosquito-vectored disease, and
become a concern. For example, salt marsh control treatments, where needed.
mosquitoes may come to inhabit areas further
inland than they did historically. Over the past few
Handbook for Mosquito Management on National Wildlife Refuges 7healthy individuals within hours of a mosquito bite
Examples of Mosquito-Borne and can last for 3 to 10 days. With any break in the
Diseases in the United States skin, there is the potential for secondary (indirect)
bacterial infection resulting from mosquito bites.
• West Nile Virus Anaphylactic reactions (life-threatening, whole-body
• Dengue Fever allergic reaction) to mosquito bites are extremely
rare. Appendix B provides a non-exhaustive
• Chikungunya
reference list and more information on mosquito-
• La Crosse Encephalitis associated health considerations.
• Eastern Equine Encephalitis
• St. Louis Encephalitis Animal Health Considerations
• Western Equine Encephalitis
Animal health can be affected by mosquito-borne
• Zika Virus
diseases. This handbook guides development
of MMPs to reduce the threat to public health
from mosquito-vectored pathogens. In general,
Mosquito-Borne Disease the Service does not manage mosquitoes for
mosquito-vectored animal disease. Mosquito
An MMP must identify which mosquito-borne management actions, such as managing non-native
diseases may be vectored by mosquitoes that breed mosquitoes that threaten endangered species,
on the refuge, either historically or currently. would follow another plan, such as an exotic
This information is helpful to identify source-area animal or invasive species management plan or an
control. Brief summaries of diseases and mosquito- endangered species recovery plan that includes
related health conditions that are potentially of a National Environmental Policy Act analysis,
concern to refuges are provided in Appendix B. and an Endangered Species Act consultation, if
Consult the Centers for Disease Control and appropriate.
Prevention or your State and local mosquito
control organization and public health authorities
for current local information. The Centers for VI. Mosquito-Vectored Pathogen
Disease Control and Prevention, National Center
for Emerging and Zoonotic Infectious Diseases
Surveillance and Mosquito
website provides links to useful mosquito-vectored Monitoring
pathogen and related diseases information, https://
www.cdc.gov/ncezid/. The U.S. Geological Survey
also provides current maps of mosquito-borne Describe the pathogen surveillance and
disease in the U.S. at: https://diseasemaps.usgs. ∑ mosquito monitoring activities used to
direct mosquito management.
gov/mapviewer/ . If there are no current or
historical occurrences of mosquito-borne diseases
in the refuge area, document that fact and the
source of the information in the MMP. Refuge staff, public health authorities, and mosquito
control organizations must rely on mosquito
Other Mosquito-Related Human Health Considerations pathogen surveillance (referred to as “pathogen
surveillance” throughout the remainder of the
There are other human health considerations handbook) and mosquito monitoring to direct
associated with mosquitoes. Most of the human mosquito management activities in order to be
population at any given time will have some most effective and minimize non-target impacts. In
reactivity to mosquito bites. Outdoor workers, general, Refuge Managers may authorize, but do
young children, immuno-defcient people, and not implement, disease surveillance and mosquito
visitors to an area with indigenous mosquitoes to monitoring. There must be mosquito monitoring or
which they have not been previously exposed are pathogen surveillance data to support treatment
at increased risk for severe reactions to mosquito decisions. The refuge staff evaluates the mosquito
bites. Though allergic reactions to mosquito bites monitoring data results against Action Thresholds
are common, the clinical diagnosis of “mosquito to guide mosquito management decisions.
allergy” is reserved for those with atypical or
systemic reactions that may occur in otherwise
8 Handbook for Mosquito Management on National Wildlife RefugesThe Refuge Manager must: decisions regarding responses to mosquito activity.
Public health authorities and mosquito control
• Identify the public health agency or organizations conduct mosquito-borne pathogen
mosquito control organization who will identifcation and surveillance. Detecting the
conduct pathogen surveillance and mosquito-borne pathogens includes testing adult
mosquito monitoring on or near the refuge mosquitoes for pathogens or testing reservoir hosts
and include the contact information and for pathogens or antibodies.
their roles in the MMP.
This is not a refuge function. Request copies of the
• Identify the on-refuge restrictions and surveillance protocols that the local public health
stipulations in a Special Use Permit (SUP) authority and/or mosquito control organization use.
for mosquito monitoring and pathogen Surveillance of mosquito-borne pathogens may:
surveillance activities (e.g., access, vehicle
use, sensitive species and/or habitats, time • Confrm the mosquito species vectoring
of day) to protect sensitive resources while a pathogen.
still allowing activities needed to make
decisions. • Identify locations where mosquitoes
vectoring pathogens breed on-refuge.
• Document the communication and
notifcation procedures between the public • Confrm pathogen incidence/prevalence.
health agency (or their authorized
representative) and the refuge. • Confrm the seasonality of pathogen
prevalence (as appropriate).
• Review the monitoring and pathogen
surveillance protocols (including objectives, • Identify and confrm locations where
methods, frequency, and locations) and pathogens (human or wildlife) occur.
include them in the MMP (and reference
in the SUP); these protocols are more Mosquito Monitoring
appropriate in the MMP than in the Inventory
and Monitoring Plan for the refuge. Mosquito monitoring identifes the mosquito species
present, relative abundance, and distribution.
• Archive mosquito monitoring and Mosquito monitoring is generally not a refuge
pathogen surveillance protocols and data function; public health or mosquito control
reports in PRIMR and ServCat, organizations usually monitor for mosquitoes.
respectively. Refuge staff should review the protocols used to
determine that each step is appropriate on the
Mosquito-vectored pathogen surveillance data will refuge and that the data will be adequate to make
include vector abundance (larval and adult forms) decisions. Mosquito monitoring protocols should
and may document mosquito-based pathogen be standardized protocols that are included in
infection rates on- and off-refuge. Monitoring the MMP, and referenced in the SUP. Repeated
vector-mosquito abundance and pathogen-related monitoring should reveal trends in mosquito
data, such as dead bird surveillance and human production over time. Public health and mosquito
disease cases, can serve as the basis for decision- control organizations use monitoring data that
making and the thresholds for pesticide treatment. they collect with standardized methodologies to
Mosquito management is adaptive management, determine if, when, where, and how to treat; to
where mosquito activity is identifed and quantifed, assess effectiveness of treatment; and to map
perhaps treated, and re-checked periodically, mosquito breeding and harboring areas to focus
often every 7 to 14 days, for activity status and, if treatment strategies. Monitoring protocols are
necessary, treatment effectiveness. developed by the State or local public health
authorities and mosquito control organizations.
Mosquito-borne Pathogen Surveillance
Objectives for mosquito monitoring are to:
The purpose of mosquito-borne pathogen
surveillance on or near the refuge is to provide • Determine if areas on the refuge exceed
the refuge staff information to make informed established action thresholds as a basis to
Handbook for Mosquito Management on National Wildlife Refuges 9determine if treatment is warranted. species in an area are known, a trained observer can
• Establish a baseline of mosquito species often identify the larvae in the feld; however, this is
present and relative abundance. not always simple or reliable.
• Identify mosquito source habitats and Identifcation keys for regions of North America
determine the relative contribution of are available for fourth instar larvae that have been
refuge sources to the regional vector collected and are examined under a microscope.
populations. Some mosquito control organizations raise numbers
of larvae to adults in rearing chambers to confrm
• Detect changes in relative abundance. that the larvae found in the area (which could
include a refuge) are the same species as the adults
• Determine the seasonality for mosquito that are causing problems. There may be situations
monitoring based on mosquito activity and where treatment will depend on the mosquito
lifestages. species (as opposed to the genus) present. It is
preferable that the public health or mosquito control
The timing and frequency of monitoring is based organization staff trained in larval (4th instar)
on such factors as life histories of mosquito identifcation conduct this identifcation. Specimens
species present, tidal cycles (if applicable), water can also be sent to local experts at State universities
temperature, water levels in wetlands, timing, or extension offces to confrm identifcation and
and volume of precipitation events, and available establish a reference collection.
resources.
2. Adult Mosquito Traps: A variety of adult
Following are examples of brief, summary mosquito traps are available for monitoring
descriptions of current mosquito monitoring purposes: sticky surfaces; fans that draw
protocols typically used by mosquito control mosquitoes into a trap; and some traps that
organizations (consult local public health district or use an attractant, such as CO2, that lures
mosquito control organization websites for other mosquitoes close enough to be drawn into a
standardized protocols): trap chamber. Traps are typically set out from
sunset to sunrise to sample during periods
1. Monitoring Larval Mosquitoes: The when most species are actively dispersing
primary technique for larval population and feeding. Counts of the species captured
counts is the dip count (using a standard dip- each trap night can indicate where adults are
cup on the end of a pole). Dips are taken in concentrating and how the adult populations are
undisturbed pools identifed as representative changing over time relative to control activities.
of the breeding areas. The trained feld person Trap sites at the refuge boundary may identify
avoids disturbing the water or casting a that the species being produced on the refuge
shadow over the water which will cause larvae are dispersing to populated areas, although
to move/dive, thereby lowering counts. For direction of fight can be diffcult to discern.
large sites, dipping would likely be conducted Mosquito control organizations sometimes
at permanent, identifed (or easily located) dip use the number, frequency, and location of
stations; although sampling location is often complaints from citizens regarding mosquitoes
random. For small sites, dips may be taken to help identify locations for mosquito
at random locations throughout the site. Dips monitoring, such as setting traps.
per site will be relative to the area needing
sampling. Recommendations for treatment of 3. Landing Rate/Bite Counts: Although
an area may be determined with fewer dips if many historical datasets include landing rate
numbers of larvae and pupae per dip exceed counts, this is not a scientifcally rigorous
action thresholds established in the refuge monitoring method and it is not recommended.
MMP (Walton, W. 2005). For mosquito monitoring on national wildlife
refuges, request that mosquito control
Standards require feld identifcation of larvae at organizations look for and implement other
least to the genus level. A trained observer can methods (see above). Landing rates, or bite
identify the following genera most of the time: counts, are equal to the number of mosquitoes
Aedes, Anopheles, Coquillettidia, Culex, Culiseta, landing on an observer in a pre-determined
Psorophora, and Uranetaenia. If the common length of time, e.g., in 1 minute intervals. This
10 Handbook for Mosquito Management on National Wildlife Refugesmethod, when repeated at multiple locations, Habitat manipulations for mosquito management
provides a rough, rapid assessment of the (such as draining or maintaining high water levels)
likelihood of being bitten in populated areas. that confict with wildlife management objectives
are prohibited except when it is necessary to
VII. Mosquito Management temporarily suspend, allow, or initiate mosquito
management activity in a refuge to protect the
Options health and safety of the public or a fsh or wildlife
population, as provided in section 8 Emergency
Power of the National Wildlife Refuge System
Describe the mosquito management Improvement Act of 1997.
options, including BMPs, habitat
∑ management, and products that may
be used on the refuge. Managing Habitats for Mosquito
Source Reduction
Source reduction is a commonly used term in
Mosquito management options can include grounds- mosquito management. Whether a refuge has
keeping activities and habitat manipulation to bogs, swamps, salt marsh, or freshwater marsh
reduce breeding habitat, and, when necessary, may habitats (collectively referred to as wetlands),
include the use of pesticides. When considering water circulation is a natural function that impedes
mosquito control measures, the Service authorizes production of mosquitoes. Since European
those methods that present the lowest risk to settlement, wetlands have been altered or degraded
our natural resources while still accomplishing by various practices such as grazing, farming,
the mosquito control goal. Always use BMPs ditching, and construction of roads and bridges.
preventively when implementing any treatment Unaltered wetlands are rare, and source reduction
option, including pesticide treatments that may techniques are not permitted in these unique
be considered. The table below provides BMPs to wetlands. In some cases, restoration of degraded or
reduce mosquito breeding habitat in and around previously altered habitat can be an effective and
facilities. economically viable option to accomplish mosquito
source reduction while also restoring natural
hydrological function. In contrast, weirs, dams, or
Best Management Practices missing or undersized culverts inhibit natural water
fow that may promote a low-fow environment for
Establish and implement a periodic review of eggs to hatch and adults to emerge before being
facilities at risk for standing water: fushed out of the system. Mosquito population
reduction may occur when a tidal marsh habitat is
• Minimize standing water to the managed to drain effectively or high marsh ponds
maximum extent possible are created or restored to serve as reservoirs
• Remove/eliminate discarded tires, road for fsh that then control mosquito larvae. Native
ruts, open tanks, or similar debris/ fsh throughout the country continue to provide
containers effective mosquito control in natural habitats. In
• Clear rain gutters to allow rainwater to coastal salt marshes, species such as Fundulus
fow freely heteroclitus, and other cyprinid fsh can exert
• Turn over containers that can hold water control over mosquitoes in the egg, larval, and
when stored outside pupal stages (Rochlin et al. 2012).
• Check for trapped water in tarps used
to cover boats/equipment and arrange Flowing water is a poor producer of mosquitoes
covers to drain water because egg masses are destroyed and larvae
• Pump out boat bilges and pupae drown. Restricting the fow of streams
• Replace water in birdbaths and livestock and rivers or channelizing these waterways may
troughs twice a week reduce riffes and rapids, which reduces fow so that
• Fix outside water faucets that are mosquitoes can breed and reproduce effectively.
dripping. Maintaining or restoring the meander and
• Use screens on rain barrels and water streambed topography will restore hydrology that
cisterns naturally prevents streams and rivers from being
sources of mosquitoes. This also diversifes the
Handbook for Mosquito Management on National Wildlife Refuges 11system, providing habitats conducive to mosquito Establishing and maintaining positive working
predators both in and out of the water. relationships is important when working with
mosquito control organizations, other State
Aquatic habitats should be supported by natural and Federal agencies, and private contractors.
hydrological processes, where possible. To do so The refuge staff will work with them from the
may require researching historic fow conditions, initial contact and planning phases through
consulting a hydrologist or restoration ecologist, implementation, monitoring, and evaluation to adopt
and coordinating with landowners up- and marsh management techniques that enhance fsh
downstream to re-establish natural fows and and wildlife benefts for the public while limiting the
conditions. You may need to clear channels creation of mosquito breeding habitats.
of accreted sediment, and remove or enlarge
structures to increase water fow into and out Mosquito Control
of the system. This may require some adaptive
management before the natural fows return,
where channels scour properly, and water fows are Describe the mosquito control
regular and consistent through the system. Wetland techniques and pesticides that may be
enhancements may re-create channels to drain or ∑ used on the refuge. The information
below may help you make better
food a poorly circulating habitat. Engineering a
tidal marsh restoration should ensure wetlands informed decisions.
have adequate circulation to almost completely
drain the marsh and allow food-up at regular daily
tide cycles. Similarly, stream restorations should be
engineered to keep water moving. Mosquito control can be accomplished with prevention
techniques, habitat management practices, pesticides,
Marsh alterations, whether for source reduction and biological controls. Each Regional offce’s
or marsh enhancement have not been without Integrated Pest Management (IPM) Coordinator
unintended consequences. Ditches used to drain reviews proposed uses of pesticides in coordination
mosquito breeding habitat on the East Coast also with the National IPM Coordinator. The public
drained high marsh pools and salt pannes important health authority or mosquito control organizations
for waterfowl and shorebirds (Cottam 1938). and the Refuge Manager must use data from various
Projects designed to restore natural hydrology may sources (e.g. scientifc literature) to identify control
also fail if, after restoration, they produce excessive products and ensure new products and technologies
mosquito populations adjacent to local communities are reviewed as they become available. The MMP
where there previously was not a mosquito breeding should include all potential products that may be
issue. For this reason, we should continually make used. In most instances, refuge staffs do not apply
efforts to develop integrated, ecologically-sound pesticides for the control of mosquitoes. If the Refuge
approaches for marsh alteration that not only Manager authorizes mosquito pesticide application
restores natural function, but also does not create through a SUP, the pesticide may be applied by
mosquito breeding habitats. the public health authority or a mosquito control
organization. The Refuge Manager must understand
The decision to consider a particular marsh for the treatment options and consequent risks to
physical alterations should begin with local, site- non-target resources, and require the use of IPM
specifc data and documentation that describes the principles to minimize pesticide use and impacts.
need for a management decision. If physical marsh Refuge staff may work with the Regional IPM
management is appropriate, the Refuge Manager Coordinator or Service environmental contaminants
may invite a technical advisory committee (TAC) of staff to make an appropriate choice of pesticide-based
Service staff and external scientists as well as local control products. Use local mosquito monitoring
partners, such as mosquito control organizations, to data provided by the public health authority or the
help evaluate a suite of potential marsh alterations. mosquito control organization when considering
The TAC recommendations may include type, extent, the pesticide products. Pesticide active ingredients
intensity of alterations, and physical and biological described below can be used to develop an MMP
metrics for post-alteration monitoring. Use BMPs and to prepare for discussions with public health
during restoration to avoid heavy equipment ruts, authorities or mosquito control organizations.
fll subsidence, or any other action that may result in
unintended temporary pools of standing water.
12 Handbook for Mosquito Management on National Wildlife Refugesa month of control, rather than the few
Mosquito Control Pesticides hours or days provided by fogging with
adulticides
Mosquito control pesticides can be categorized into • The commonly used mosquito larvicides
three classes: larvicides, pupacides, and adulticides. are less toxic than the adulticides and are
There are relatively few products available within applied in such a way that there is much
each of these classes, and all differ with regard to less human exposure
effcacy and effects on non-target organisms. Active • Mosquito larvicides generally are applied
ingredients in these pesticide products may include: to smaller areas than are adulticides
chemicals, naturally occurring bacteria, analogs of
insect molting hormones, and monomolecular oils as Larvicides. Larvicides are pesticides that
well as inert ingredients. The USEPA registration affect the four instars of mosquitoes. The most
process for pesticide products considers primarily the common mosquito larvicides are derived from
toxicity and environmental persistence of the active natural bacteria or act on insect-specifc pathways
ingredient. In many pesticide products, the active not shared by other insect species. Spinosad,
ingredient is combined with “inert” ingredients that s-methoprene, and Bacillus-based Bacillus
alter the environmental behavior of the chemical. thuringiensis israelensis (Bti) or Lysinibacillus
All inert ingredients in USEPA registered pesticide sphaericus (Ls), the main active ingredients,
products are pre-approved before being used in a have unique routes of exposure and modes of
pesticide product formulation (USEPA 2015). These toxicological action against larval mosquitoes. The
inert ingredients are added to increase activity or route of exposure and mode of action infuence
modify a physical property such as increase the their non-target toxicity relative to each other
bulk of the product, lengthen its persistence in the and to other types of chemical insecticides. They
environment, or otherwise improve its ability to reach can be applied through a variety of methods
the target species. While these inert ingredients are including hand application via backpack sprayers,
not intended to have non-target toxicity, in some cases low-pressure amphibious tracked vehicles, truck-
they do. mounted equipment, and aerial sprayers. Spinosad
and s-methoprene work via contact rather than
If mosquito control measures using pesticides are ingestion. Bacillus-based products have lower
necessary, the Refuge Manager’s next goal is to risk to non-target organisms in part because they
ensure that the public health authority or mosquito must be ingested by the insect and are activated
control organization selects products for on-refuge at a high pH that occurs almost solely in the gut
use that minimize natural resource non-target of mosquitoes, midges, and black fies. As with all
impacts. Products allowed for use on-refuge should pesticide use in the Service, we review and approve
correspond with the information known about: or decline to approve the use of larvicides through
the Pesticide Use Proposal System.
• Mosquito species and targeted life stage
• The breeding habitat Preferred Active Ingredients
• Density of larval populations Bacillus thuringiensis israelensis (Bti) is a natural
• Temperature soil bacterium that acts as a larval mosquito
• Effcacy of the products stomach poison. Bti must be ingested by the larval
• Potential impacts to non-target resources form of the insect in order to be effective. Bti
• Resistance management contains crystalline structures that have protein
• Costs endotoxins that are activated in the alkaline
conditions of an insect’s gut. These toxins attach
Following the long-standing IPM principles, the to specifc receptor sites on the gut wall and,
Service continually strives to minimize exposure of when activated, destroy the lining of the gut and
non-target refuge natural resources to pesticides. eventually kill the insect. The toxicity of Bti to an
Therefore, in general mosquito adulticide products insect is directly related to the specifcity of the
are not used on refuges. Larvicides are preferred toxin and the receptor sites. Without the proper
over mosquito adulticides for several reasons: receptor sites, the Bti will pass through the insect’s
gut. Bti is most effective on frst, second, third and
• Use of mosquito larvicides prevents the early fourth instar larvae. The earlier instars feed
appearance of the blood feeding adults at a faster rate (late fourth instar larvae feed very
• Mosquito larvicides can provide up to little) and require ingestion of fewer crystals to
Handbook for Mosquito Management on National Wildlife Refuges 13induce mortality. Bti has been shown to have toxic the mosquito larvae will continue to feed and may
activity against mosquitoes, black fies, and certain reach pupal stage, but the S-methoprene interferes
species of midge; no direct effects of Bti toxicity with the maturation of the pupa and they will not
have been found for aquatic invertebrates and this emerge as adults. The mosquito third and fourth
profle is preferred for use on a refuge. Bti has larval instars are the most susceptible stages of
limited acute and no chronic toxicity to mammals, development when exposed to S-methoprene.
birds, fsh, or vascular plants (USEPA 1998). Bti- Mammals, birds, fsh, reptiles, and amphibians do
based products with labels indicating effcacy for not have this juvenile hormone nor do they share
1-2 weeks are preferred for use on refuges, however this biochemical pathway, which is what makes
a number of product labels indicate effcacy for up S-methoprene a relatively targeted insecticide.
to 40 days, and the activity of Briquet formulations S-methoprene is essentially non-toxic to mammals,
can last for months. has some limited toxicity to birds, amphibians, fsh,
and certain non-target freshwater invertebrates,
Lysinibacillus sphaericus (Ls) is a registered and some marine crustaceans, that share
larvicide, and few feld studies have examined similar biochemical pathways to those on which
its non-target effects. Data available indicate a S-methoprene acts in target organisms. Hormones
high degree of specifcity of Ls for mosquitoes, act on biological systems at exceedingly low levels,
with no demonstrated toxicity to midge larvae at thus, a very low concentration of S-methoprene
mosquito control application rates (Mulla 1984; Ali is required in the environment to control target
1986; Lacey 1990; and Rodcharoen 1991). Some Ls organisms. This fact, combined with its low toxicity
product labels indicate effects lasting for as long as to birds and mammals makes S-methoprene a useful
four weeks. mosquito larvicide alternative that can be used in
an integrated approach. Products are available
Less Preferred Active Ingredients in several formulations: liquid, granular, pellet,
Spinosad is derived from two fermentation and briquette. There are several extended-release
products of a soil actinomycete bacteria formulations that remain effective for up to 150
(Saccharopolyspora spinosa), the spinosyns A days. Due to the fact that S-methoprene can act
and D. Spinosad is a contact neurotoxin that on invertebrates that share the juvenile hormone
disrupts the nicotinic acetylcholine receptors in and biochemical mode of action as well as the active
insects. This mode of action is similar to that of ingredients persistence, it is less preferred for use
the neonicotinoid insecticides, and similar to the on refuges (Pinkney et al. 2000).
organophosphates which act on a different receptor
in the same biochemical system. Due to the mode Not Recommended for Use on Refuges
of action on a pathway that is conserved across Organophosphate mosquito larvicides (e.g.,
taxa, spinosad acts on a broad array of insects. temephos) inhibit the enzyme acetylcholinesterase
Products designed to increase the environmental by binding it irreversibly and cause cumulative
persistence of spinosad have been found to enable effects in animals repeatedly exposed to these
target (mosquito) and non-target toxic effects chemicals. This biochemical pathway is essential
that can persist for several weeks (Duchet et al. to nerve function in insects, humans, and other
2015; Lawler and Dritz 2013). Due to spinosad’s animals, and the effects of exposure are cumulative,
mode of action that impacts a diversity of aquatic therefore, safer alternatives are preferred.
invertebrates and its persistence, this active The USEPA banned most residential uses of
ingredient is less preferred for use on-refuge than organophosphates in 2001, but they are still used in
the Bacillus-based products. agriculture and for control of larval mosquitoes.
S-methoprene is a synthetic mimic of the naturally Surface Oils and Films. Surface oils and flms are
produced insect juvenile hormone (JH); it is applied to aquatic mosquito breeding sites to kill
commonly referred to as an insect growth regulator. mosquito larvae and pupae. The products create a
Mosquitoes produce JH in the larval stages, barrier to the air-water interface and suffocate the
with the highest levels occurring in the early insects, which generally require periodic contact
developmental stages. As an insect reaches the with the water surface to obtain oxygen. Surface
fnal stages of larval development, the JH level is oils can prevent female mosquitoes from landing
low. This low level of JH triggers the development to lay eggs. Due to the broad-spectrum action of
of adult characteristics. When S-methoprene is surface oils and flms, they are not appropriate
applied directly to larval mosquito breeding habitat, and are rarely authorized for use on refuges. The
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