5A - Wetland permit application to allow mosquito control measure to reduce the threat of West NileCITY OF BOULDER
PLANNING BOARD AGENDA ITEM
MEETING DATE: May 15, 2003
(Agenda Item Preparation Date: May 9, 2003)
AGENDA TITLE:
Public hearing and consideration of wetland permit application to allow mosquito control
measures to reduce the threat of West Nile Virus.
Applicant: City of Boulder, Department of Environmental Affairs, Alice Guthrie
REQUESTING DEPARTMENT:
Planning and Development Services:
Peter Pollock, Planning Director
Maureen Rait, Director of Public Works for Development and Support Services
Jeff Arthur, Engineering Review Manager
Varda Blum, Floodplain and Wetland Permitting, Planning & Development Services
OVERVIEW:
This item requests Planning Board's decision on the wetland permit application to apply
microbial treatment to wetlands on lands owned by the city of Boulder where larvae of the
species of mosquitoes that transmit West Nile virus have been found. Because of the time
constraints surrounding commencement of tha control plan, the public health issues involved,
and the high interest level of Planning Board in the permit application, this item has been
refened to Planning Board for decision. This is in accordance with Section 9-12-7(c), B.R.C.
1981 which allows the city manager to refer any wetland permit application to the Planning
Boazd for decision. Key issues include determination of whether the proposed West Nile
Virus Control Plan meets the standards for activities which may be permitted in regulated
wetlands. Staff has reviewed the application and recommends approval of the permit with
conditions based on a finding that the applicable standards for wetland permits have been met.
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KEY ISSUES:
Can the proposed activity be permitted under Section 9-12-8, "Standards for Wetland Permits,"
Boulder Revised Code, 1981?
1. Has the applicant for the wetland permit for the West Nile Virus Control Plan
demonstrated that all impacts on wetlands have been avoided through a reduction in the
size, scope, or density of the project or a change of project configuration or design or that
it is not feasible to do so? (Section 9-12-8(a), B.R.C. 1981)
2. Has the applicant demonstrated that any impact on a wetland has been minimized, will
result in minimal impact or impairment to any wetland function, and will not jeopardize
the continued existence of habitat for identified plant, animal, or other wildlife species?
(Section 9-12-8(b), B.R.C. 1981)
3. Has the applicant demonstrated that the project is in the public interest, considering the
public need, the functional values of the wetland that may be affected, the extent and
permanence of any adverse effects, and the uniqueness and scarcity of the wetlands that
may be affected? (Section 9-12-8(c), B.R.C. 1981)
BACKGROUND:
The city of Boulder is proposing to implement mosquito control measures to reduce the threat of
West Nile Virus (a mosquito-borne virus) to the city's residents. Two Colorado species of
mosquito aze known to transmit West Nile virus to humans. Starting in May, all of the
approximately 1,700 acres of wetlands regulated by the city of Boulder will be surveyed to
determine if either of these two species occurs. Control measures include treatment of wetlands
with bacteria that attacks mosquito larvae. The wetland permit application addresses any
wetland where larvae of either of the two species of mosquitoes is found. Control of the larvae
will limit the possible future need for nonbiologica] control of adult mosquitoes. This control
plan was formulated in conjunction with the Boulder County Health Department.
Impacts to the wetlands include the potential for killing not only the targeted mosquito larvae,
but other inver[erbrates of the order diptera (flies). Although the applied bacteria generally
dissipate within a few days, the affected species of flies will likely not repopulate the wetlands
until the next year.
The proposed control plan was presented at the City Council meeting on April 15, 2003. City
Council had no objections to the proposed approach of performing larval control on the targeted
mosquito species. Therefore, the Department of Environmental Affairs has proceeded with the
larval control plan and submitted a wetland permit application for the proposed activity to
Planning and Development Services.
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ANALYSIS:
Key Issue: Can the proposed activity be permitted under Section 9-12-8, "Standards fbr
Wetland Permits," Boulder Revised Code,1981?
Has the applicant for the wetland permit for the West Nile Virus Control Plan
demonstrated that all impacts on wetlands have been avoided through a reduction
in the size, scope, or density of the project or a change of project configuration or
design or that it is not feasible to do so? (Section 9-12-8(a), B.R.C. 1981)
This standard is intended to address impacts of proposed development on wetlands. Although uo
development is being proposed, this standard is being applied to this wetland permit application
as a means of determining whether the applicant performed appropriate alternatives analysis.
Boulder County Health Department controls mosquitoes within the county with a mosquito
control plan that targets both adult and larval mosquitoes. The applicant rejected the option of
adopting a similar program because of the larger environmental impacts that result from such a
program. The applicant evaluated seven alternatives for controlling the threat of West Nile virus,
and ranked the alternatives according to their projected impact on wetlands. The attached
wetland permit application contains a complete discussion of the seven alternatives. The chosen
alternative involves applying a microbial insecticide ("Bti") only to those wetlands where larvae
from either of the two species of mosquitoes has been found. The insecticide generally dissipates
within a few days. With the exception of the "no action" alternative, the chosen altemative has
the least potential impact to wetland functions. The applicant rejected the "no action" aiternative
because of the need to protect public health.
Staff finds that the altemative analysis was comprehensive and appropriate and that the proposed
activity meets standard BRC 9-12-8a.
2. Has the applicant demonstrated that any impact on a wetland has been minimized,
will result in minimal impact or impairment to any wetland function, and will not
jeopardize the continued existence of habitat for identiTied plant, animal, or other
wildlife species? (Section 9-12-8(b), B,R.C. 1981)
Impact to the wetlands will be minimized by following "City of Boulder Wetlands Protection
Program Best Management Practices" during testing and treatment of wetlands. However,
application of Bti will reduce the abundance and diversity of aquatic life within any of the
wetiands that are treated. Because part of the food chain is temporarily removed by killing the
larvae, the functional value of the wetland as fish and wildlife habitat will be reduced. This
effect should be temporary. The affected species of flies and mosquitoes are likely to return in
the next year.
Staff finds that that the applicant has minimized wetland impacts by choosing the least obtrusive
way of controlling the threat of West Nile virus. In addition, the proposed larval testing and
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treatment will result in minimal impact or impairment to the wetland. Finally, because the effect
is temparary, the proposed treatment will not jeopardize the continued existence of habitat.
Therefore, staff finds that the proposed activity meets standard BRC 9-12-8b.
3. Has the applicant demonstrated that the project is in the public interest, considering
the public need, the Functional values of the wetland that may be affected, the extent
and permanence of any adverse eFfects, and the uniqueness and scarcity of the
wetlands that may be affected? (Section 9-12-8(c), B.R.C. 1981)
The Boulder County Health Department considers West Nile virus a serious public health threat.
City Council has concurred with the Health Department and directed the Department of
Environmental Affairs to proceed with a West Nile Virus Control Plan. Despite the city's history
of not performing mosquito control within the city of Boulder, the Department of Environmental
Affairs acknowiedged the need for a control and chose the proposed plan as the best balance
between effectiveness and low impact in the wetlands. Direct impacts to the regulatory wetlands
are the minimum necessary to provide for the required mosquito control to protect the public
from the threat of West Nile virus.
Staff finds that the proposed activity is in the public interest and therefore meets standard Section
9-iz-s~~~, B.R.c. i9si~.
PUBLIC COMMENT & PROCESS:
Required public notice of the wetland permit application was given in the form of an
advertisement printed in the News from City Hall, in the Sunday Daily Camera, on Apri120,
2003. In addition, prior to treatment of a wetland, posting will occur at the wetland to be treated.
This item has been referred by the Planning Director to the Planning Board and notification of
this hearing was made in the News from City Hall, in the Sunday Daily Camera, on May 4, 2003.
It was not possible to mail a written notification as required by Section 9-12-6(d), B.R.C. 1981
because it is not yet known which wetlands will be affected. It is also not possible to post ten
days prior to the comment deadline at each wetland to be treated as required by B.R.C. 9-12-6
(e). This would be too long a timeline to allow effective treatment of the wetland. These
notification requirements were suspended by the city manager under Section 9-12-14, B.R.C.
1981, Emergency Exemptions.
STAFF RECOMMENDATION:
Considering the standards outlined under Section 9-12-8, B.R.C. 1981, staff finds that the
proposed project meets the intent of Section 9-12-1, B.R.C. 1981. Therefore, it is recommended
that Planning Board approve the wetland permit application for the West Nile Virus Control Plan
adopting this memorandum as findings of the Board and subject to the following conditions:
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1. Mosquito treatment activities shall conform to the "City ofBoulder Wetland Permit
Application for City of Boulder West Nile Virus Control Plan" prepared by Greystone
Environmental, dated Apri121, 2003.
2. All work activities in the regulatory wetland and wetland buffer area shall comply with
the "City of Boulder Wetlands Protection Program Best Management Practices (BMPs)
and Revegetation Rules."
3. Prior to application of microbial insecticide to a wetland, a notice will be posted at the
wetland to be treated. The notice will remain for seven days or until the wetland is
retested for the tazget mosquito larvae.
4. The applicant shall maintain documentation of the wetlands which have received
treatment with microbial insecticide. This documentation shall be transmitted to
Planning and Development Services at the end of the treatment period or when requested.
In addition, the applicant shal] document any adverse effects on wetlands beyond the
effects on targeted larvae and flies described in the permit application, and notify
Planning and Development Services of these impacts.
Approved By:
, ~ -
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.h,/ Peter Poll ck, Planning Director
/
ATTACHMENTS:
A Apri121, 2003 Draft City of Boulder West Nile Virus Control Plan
B Wetland Permit Application for West Nile Virus Control Plan
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ATTACHMENT A
PRELIMINARY DRAFT
CITY OF BOULDER
WEST NILE VIRUS CONTROL PLAN
Prepared by:
Crreystone Environmental Consultants
5231 South Quebec Street
Greenwood Village, Colorado 8011 I
April 2003
Agenda Item # ;7~ Page # ~'
TABLE OF CONTENTS
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1.0 Introduction ............................................................................................................................ ....... 1-1
1.1 Background ......................................................................................................................... .......1-1
1.2 Goals and Objectives .......................................................................................................... ....... 1-1
2.0 Mosquito-Borne Diseases that May Occur in the Boulder Area ............................................ ....... 2-1
2.1 WestNi]eVirus .................................................................................................................. .......2-1
2.1.1. Status of West Nile Virus in Colorado .................................. :................................... ....... 2-1
2.2 Western Equine Encephalitis .............................................................................................. ....... 2-1
2.3 Saint Louis Encephalitis ..................................................................................................... ....... 2-1
2.4 Califomia Encephalitis ....................................................................................................... ....... 2-2
3.0 General Overview of Mosquito Habitat and Biology ............................................................. ....... 3-1
3.1 Larval Habitat .....................................................................................:............................... ..:.... 3-1
3.1.1. Classification of Breeding Sites ................................................................................. ....... 3-1
3.2 AdultHabitat ...................................................................................................................... .......3-1
3.3 General Mosquito Biology ................................................................................................. ....... 3-1
3.3.1. Eggs ............................................................................................................................ .......3-1
3.3.2. Larvae ......................................................................................................................... .......3-2
33.3. Pupae .......................................................................................................................... ....... 3-2
33.4. Adult ........................................................................................................................... .......3-2
4.0 Methods and Materials for Larval Mosquito Control ............................................................. .......4-1
4.1 Preferred Larval Control Agents ........................................................................................ .......4-1
4.1.1. Application of Bacillus thuringiensis israelensis ........................................................ .......4-1
4.2 Optional Methods and Materials for Larval Mosquito Control .......................................... ....... 4-2
4.2.1. Application of Bacillus sphaericus ............................................................................. .......4-2
4.2.2. Mosquito Habitat Manipulation .................................................................................. ....... 4-2
43 Methods and Materials Considered but not Recommended for Larval Mosquito Control. ....... 4-2
43.1. Application of Methoprene ......................................................................................... .......4-2
4.3.2. Introduction of Predatory Fish .................................................................................... ....... 4-3
4.33. Application of Oils .......:............................................................................................. .......4-3
4.4 Surveillance of Larval Mosquitoes ..................................................................................... ....... 4-3
4.4.1. Objective ..................................................................................................................... ....... 4-3
4.4.2. Background ................................................................................................................. .......4-3
4.4.3. Activities Planned ....................................................................................................... ....... 4-4
4.5 Control of Larval Mosquitoes ............................................................................................. ....... 4-4
4.5.1. Objective ..................................................................................................................... ....... 4-4
4.5.2. Background ................................................................................................................. .......4-4
4.53. Planned Activities ....................................................................................................... .......4-6
4.5.4. Larval Mosquito Control Thresholds ......................................................................... ....... 4-7
4,5.5. Planned Activities for Larval Thresholds ................................................................... .......4-7
5.0 Methods and Materials for Adult Mosquito Control .............................................................. ....... 5-1
5.1 Adult Control Agents ......................................................................................................... ....... 5-1
5.1.1. Application of Permethrin .......................................................................................... ....... 5-1
5.1.2. Application of Resmethrin .......................................................................................... ....... 5-1
5.1.3. Application of Sumithrin ............................................................................................ ....... 5-1
5.2 Surveillance of Adult Mosquitoes ...................................................................................... ....... 5-2
5.2.1. Objective ..................................................................................................................... ....... 5-2
5.2.2. Background ................................................................................................................. .......5-2
5.23. Activities Planned .........:............................................................................................. ....... 5-2
5.3 Control of Adult Mosquitoes .............................................................................................. ....... 5-5
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Table ofContents
53.1. Background .........................................................................................
53.2. Activities Planned ...............................................................................
533. Adult Mosquito Control Thresholds ...................................................
53.4. Assessment and Summary ..................................................................
5.3.5. Planned Activities for Adult Mosquito Thresholds ............................
5.3.6. Assessment and Summary ..................................................................
6.0 Potential Impacts of Bti to Nontarget Species ................................................
7.0 Potential Impacts to Water Quality from Bti ..................................................
8.0 Education ........................................................................................................
8.1 Research and Evaluation ............................................................................
8.1.1. Back~-ound .........................................................................................
8.1.2. Activities Planned ...............................................................................
8.13. Obj ective .............................................................................................
8.1.4. Activities Planned ...............................................................................
8.2 Public Educarion and Outreach ..................................................................
9.0 2003 Summary Report ....................................................................................
10.0 Glossary ..........................................................................................................
11.0 References ......................................................................................................
TABLE
Table G-1: Literature Review of Toxic Effects fmm Bacillus thuringiensis subspecies israelensis on Non-
target Organisms ................................................................................................................................ 6-2
FIGURES
Figure 3-1 Mosquito Life Cycle ...............................................
Figure 4-1 Larval Surveillance Flowchart ................................
Figure 4-2 Larval Mosquito Control Flowchart .....:.................
Figure 5-1 Adult Surveillance Flowchart .................................
Figure 5-2 Adult Mosquito Control Flowchart .........................
APPENDICES
Appendix A Classification of Breeding Sites
Appendix B Material Safety Data Sheet
................... 3-4
................... 4-5
................... 4-9
................... 5-4
................... 5-9
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1.0 INTRODUCTION
~ ~
The City of Boulder is proposing to implement mosquito control measures to reduce the threat of West
Nile Virus (WNV, a mosquito-borne virus) to the city's residents. Two species of mosquito in Colorado
are lmown to transmit West Nile Virus to humans: Culex pipiens and Culex tarsalis. Star[ing in May,
wetlands regulated by the City of Boulder will be surveyed to evaluate whether either of these two species
occurs. Areas that will be surveyed include all city-owned lands within the city limits (approximately
311 acres) and at least a portion of the approximately 1,400 acres of the city-owned Open Space lands
outside of the city limits. Larval control measures will consist of treahnent of wetlands with a bacterium
that attacks mosquito larvae (Bacillus thuringiensis israelensis, or Bti). The weUand permit application
addresses any wetland where larvae of either of the two species of mosquitoes is found. Control of the
larvae will limit the possible future need for nonbiological control, such as chemical pesticide spraying, of
adult target mosquitoes.
The level of risk from mosquito-bome disease depends on the number of mosquitoes that are capable of
transmitting the virus, the prevalence of the virus among them, and the density of the human population. in
an area where WNV is found. Proper surveillance of larval mosquitoes is an important component in
identifying areas that are at high risk for transmission of WNV to humans. The results of surveillance
should be used to guide prevention and control. Surveillance of larvae can provide information on the
expected abundance of adult mosquitoes and can indicate areas where control efforts should be directed.
Control efforts during the larval stage are the most cost-effective and efficient means to eliminate
mosquitoes at their source and, therefore, to most effectively reduce the risk of human infection.
1.1 BACKGROUND
The City of Boulder has historically not conlrolled mosquitoes, in accordance with its Integrated Pest
Management (IPM) policy, The city's policy provides a decision-making process for pest management
that emphasizes selection of the most environmentally sound method for mosquito control. In contrast,
the Boulder County Health Department has controlled nuisance mosquitoes within the county through the
Boulder County Mosquito Control District. The county's activities have resulted in control of both larval
and adult mosquitoes. The Boulder County Mosquito Control District is delineated by the county
commissioners and is funded by a Yax on the residents of the district. Tjae Cjtiy!pf Souli~er.xs;XC:sp¢nsiblg
,.
f,ar fu~1di11g itS :3ilVr~ irios{jUitA'COnixol=effo~ks„i.~~tle27 The city and county are using two different entities
for managing mosquito conhol programs. However, the overall approach is a collaborative effort between
the city and county and other goveming agencies that are involved in minimizing the risk to human health
from WNV.
1.2 GOALS AND OBJECTIVES
The overall goal of this WNV control effort is to reduce the risk of human WNV infection while
providing the most limited effect to the environment possible. This goal will be achieved through a
mosquito control program that is responsive to the public, environmentally sound, cost-efficient, and
consistent with county requirements. This plan is directed primarily at the larval stages of mosquitoes
and their sources. Control will generally be contained in ]ocalized areas and will have minimal
environmental impacts. Control of adult mosquitoes may be included, but only in emergencies, and is not
the emphasis of this plan. The comprehensive nature of this plan ensures the efficacy of the control
measures while minimizing adverse impacts to human health and the environment.
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I.0 Inhoduction
The objectives that will be used to accomplish this goal are
Objective 1: Map (in geographic information system [GIS] format) potential mosquito breeding habitats
within city-owned lands, This map will allow accurate tracking of data for efficient and effective conrtol
and will provide reliable information for recommendations for control in 2004.
Objective 2: Identify the habitats that support the two target species. Identification will allow treatment
of only the weUands that contain the two target species and will reduce the number of wetlands where
treatment is necessary. Many other control programs treat all habitats where significant mosquito
populations are found, regardless of the species. Targeted control will substantially reduce the
environmental impacts to the city's wetlands.
Objective 3: Apply the larvicide (Bti) to any wetlands where either of the two target species is found.
This level of control effort conducted during the larval stage is the most effective and environmentally
friendly way to eliminate the target mosquito species. Therefore, this effort reduces the potential for
WNV-carrying adult mosquitoes to hatch. This approach will lower the likelihood of the possible need for
adulticide spraying if WNV tums into an epidemic.
Objective 4: Collect data on the locations of actual WNV outbreaks (for mosquitoes, birds, and
mammals) within lands owned by the City of Boulder. Data collection will include: (a) conducting direct
WNV testing within the adult mosquito populations of the two target species; and, (b) coordinating with
local and state agencies on the results of WNV findings for birds and mammals within the ciTy.
Objective 5: Develop a public education and awareness program, including a West Nile Virus Control
Plan . This plan will inform the public about the need far the control efforts and will describe what the
control efforts will entail. Other efforts include preparing an information pamphlet that will be distributed
with the utility bill.
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2.0 MOSQUITO-BORNE DISEASES THAT MAY OCCUR IN
THE BOULDER AREA
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There are currently four arboviruses found in Colorado that are transmitted by mosquitoes: West Nile
Virus, Westem Equine Encephalitis, St. Louis Encephalitis, and Califomia Encephalitis. Arbovirus, short
for arthropod-bome virus, is a virus group spread mainly by blood-sucking insects such as mosquitoes.
Encephalitis is an acute inflammation of the brain tissue. It can be caused by a variety of agents, but
viruses are the most common cause. The following paragraphs discuss these various viruses.
2.1 WEST NILE VIRUS
WNV was first found in the United States in 1999 in New York City and has since spread to 43 states
(USGS 2002). WNV is an arbovirus, a virus iransmitted by arthropod hosts. The virus is primarily
transmitted by mosquitoes of the genus Culex. In Colorado, the mosquito species Culex tarsalis and
Culex pipiens are Imown to be involved in the transmission cycle of the virus. C. tarsalis is considered
more likely to transmit the virus to mammals, such as horses and humans, which are dead-end hosts.
2.1.1. Status of West Nile Virus in Colorado
Because the status of WNV in Colorado is changing rapidly, the most current infortnation on WNV in the
state can be found by referring to the Colorado Department of Public Health and Environment web page
at:
htLp://ww«~.cdkhe,state.co. us/de/zoonosis/wnv/wnvhom.hCnil.
For additional information on the WNV, refer to the Centers for Disease Control web page at:
httu://ww~v.cda eo v/ilcidod/dvbid/westnilc/index.htm.
2.2 WESTERN EQUINE ENCEPHALITIS
Western Equine Encephalitis (WEE) is an arbovirus that is found throughout North, Central, and South
America. However, the majority of the cases in North America have been reported from the rural western
United States. WEE is spread mainly by the vector mosquito Culex tarsalis. Birds are the primary hosts
for WEE because of their ability to act as reservoirs to the virus and allow it to replicate easily (Leighton
2000). Birds are infected in the spring by virus-carrying mosquitoes; the virus replicates and amplifies in
the birds, other mosquitoes feed on the birds, the newly infected mosquitoes can infect more birds, and
the cycle continues. Humans and horses are described as dead-end hosts for the virus because, once it has
been contracted, they cannot transmit the disease. WEE is common in the summer, with peaks in July
and August when populations of the vector mosquito are the highest (Nadalur 2002), The risk of disease
in humans and horses varies from year to year depending on the number of infected mosquitoes. A
vaccine is available for horses, but there is no vaccine for general use in humans because of the small
amount of verified WEE cases.
2.3 SAINT LOUIS ENCEPHALITIS
The St. Louis Encephalitis (SLE) virus was first recognized in 1933 in St. Louis, Missouri. Currently, the
virus occurs throughout the United States, with higher concentrations in the Mid-West and Southern
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~ 2.0 Mosquim-Boume Diseases ~hat May Ocwr in the Bouldcr Area
states with small (fewer than 30 people affected), isolated regional outbreaks (CDC 2001). Birds are
immune hosts of the virus, which is transmitted between birds and from birds to humans and other
animals by the blood-sucking mosquitoes (CDC 2001). The virus is transmitted and spread primarily by
mosquitoes of the genus Culex. As with WEE, humans are a dead-end host for SLE. Most humans that
are infected never show any symptoms of the disease. Currently, there is no vaccine against SLE.
2.4 CALIFORNIA ENCEPHALITIS
The California Encephalitis (CE) virus was first named after a human case diagnosed in 1946 in Kern
County, California (Soliman n.d). Since that time, most cases have been linked with the La Crosse virus.
The La Crosse virus occurs in north-central states, primarily in the upper Mississippi River Valley, and is
transmitted by the treehole mosquito, Aedes triserlatus. The vertebrate hosts of the virus are primarily
small woodland mammals, such as squirrels and chipmunks, who harbor the virus until it is passed to
other mosquitoes. Uniquely, the virus is able to survive the winter within the vector mosquito (CDC
2001). Only about 70 cases of La Crosse encephalitis are reported annually.
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3.0 GENERAL OVERVIEW OF MOSQUITO HABITAT AND
BIOLOGY
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3.1 LARVAL HABITAT
Mosquitoes successfully inhabit almost every kind of collection of watec A"breeding site" is any place
that will hold water for a week or more after rainfall. Prime breeding sites include marsh edges, short
grass ditches, tire ruts, hoof prints, discuded tires left outdoors, poorly maintained bird baths, clogged
rain gutters, unused swimming and plastic wading pools, pots and pans with standing water, and anything
eise that will hold stagnant water (NYCDHMH 2O03; MMCD 2002). The most prolific breeding sites for
the City of Boulder may include flood-irrigated lands, and seasonally weddry locations with stagnant
water.
Some mosquitoes develop in permanent water and semi-permanent water. Examples of these kinds of
sites include cattail marshes, ponds, and unused swimming pools. Other mosquitoes develop in tree holes
and artificial containers, including waste tires and buckets.
Some areas that do not support mosquitoes include moving water (rivers, streams, and creeks), deeper
lakes, ornamental ponds, and duck ponds. Other conditions that are unfavorable for mosquito production
are turbulence and the presence of natural enemies.
3.1.1. Classification of Breeding Sites
Breeding sites are classified according to habitat type using criteria developed by the U.S. Army Corps of
Engineers and the U.S. Fish and Wildlife Service. A description of the eight major wetland habitat types
is included in Appendix A.
3.2 ADULT HABITAT
In the daytime, adult mosquitoes avoid adverse environmental conditions, such as intense heat, by taking
refuge in resting areas known as "harborage." Harborage areas are resting locations composed of natural
vegetation and include forests, tree stands, grass, shrubs, or foliage. Ideal resting areas are generally
shaded with cooler daytime temperatures and high relative humidity. These conditions are typically
found in forests or tree stands that have a canopy, dense underbrush, and with or without adjacent wetland
areas. Other resting sites include culverts, hollow ]ogs, underneath decks, shaded sides of buildings,
basements, and garages.
3.3 GENERAL MOSQUITO BIOLOGY
3.3.1. Eggs
All mosquitoes must develop in water before they can fly. The adult female mosquito, after taking a
blood meal, will search for a place to lay her eggs. Culex mosquitoes lay eggs in clusters, rafts, or singly
on the water surface.
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3.0 General Overview of Mosquito Habitat and Biology
3.3.2. Larvae
Larvae develop in shallow water. They have four growth stages lmown as instars (Figure 3-1). They are
found in the water hanging head down just below the surface. The larvae use a respiratory siphon that
breaks the surface of the water to breath. The siphon is located at the tail end of the long, slender body.
When larvae first hatch, they are less than 1/8-inch long, and they grow to be 3/8-inch long by the fourth
instar. Mosquito larvae are also referred to as wrigglers because of their jerky movements in the water.
Culex tarsalis larvae are found in a wide variety of semipermanent and permanent sources of water in
both rural and urban areas (Nielsen et al. 2002). They occupy a wide varieTy of either fresh or polluted
water habitats, usually in open, sunlit locations (Harmston and Lawson 1963).
Culex pipiens larvae are found in a wide variety of natural and artificial sources that are often highly
polluted with organic wastes (Nielson et al. 2002; Harmston and Lawson 1963). They have been found in
containers of various types, catch basins, ornamental pools, cesspools, swimming pools that are not
completely drained, ditches, and tree holes (Nielsen et al. 2002).
3.3.3. Pupae
At the end of the fourth instar, the larva molts into a pupa. The pupa is a cocoon-like stage when the adult
mosquito is forming, and typically lasts about 2 days. The mosquito does not feed during the pupa stage,
but when disturbed, will tumble as it avoids danger. The pupa is also ]mown as a tumbler.
3.3.4. Adult
The adult is fully formed after about 2 days as a pupa. The adult mosquito breaks through and emerges
from the pupal skin. It rests for a short time on the water surface while its wings expand and dry. Male
mosquitoes emerge first and form a swarm where they will mate with emerging females. Females mate
only once, and store sperm in their bodies to fertilize eggs as they are laid. Once the female has mated,
she flies off in search of a blood meal to obtain the proteins necessary for laying eggs. Females also feed
on plant nectar for energy; males feed only on plant nectar.
A number of factors influence the blood feeding of the adult female: humidity, wind, temperature, light,
and animal emanations (such as respiration or body heat). For most mosquitoes, the primary period for
feeding on blood is between sunset and midnight during the summer. A second feeding period occurs
around sunrise. This feeding behavior may change during the spring and fall, when daytime conditions
favor mosquito activity over evening conditions. Temperatures above 55 degrees F and humidity levels at
or in excess of 70 percent are optimum feeding conditions.
Culex tarsalis, the main canier of West Nile Virus, breeds several generations per year. Eggs are laid in
rafts on the surface of permanent and semi-permanent clear ground pools, springs, and ditches. In late
summer, egg laying spreads to temporary pools and containers that contain standing water. Females
overwinter in protected places, including caves, abandoned mines, and cellars (Harmston and Lawson
1963). Adults prefer to feed on birds, but will bite humans and other mammals (Nielson et al. 2002;
Harmston and Lawson 1963). Feeding occurs near dusk and after dark (Nielsen et al. 2002). Its life cycle
varies from 4 days to 30 days, depending on conditions. Culex tarsalis can also travel up to 2 miles for a
blood meal. Collections have been made at elevations up to 10,000 feet (Harmston and Lawson 1963).
Agenda Item # . `~H Page #~
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3.0 General Overview oCMosquito Ha6itat and Biology
Culex pipiens breed quickly and use standing or slow-moving water that contains decaying organic
materials to lay eggs. Females hibernate in cellars, basements, and other protected sites (Harmston and
Lawson 1963). Birds are major hosts, and studies show that C. pipiens takes blood meals from them
mare than 95 percent of the time. Mammals constitute the rest, with humans representing less than 1
percent of the total (Nielsen et al. 2002).
Mosquitoes of the genus Culzr (Culer tarsalis and Culex pipiens) overwinter as gravid (egg bearing)
females. This characteristic results in low populations in the spring but that undergo geometric growth
during August and September. Because the population is greatly increased in the late summer, potential
vectors and disease transmission are most prevalent at this time (BCMCD 2002). They overwinter as
adults in caves, hollow logs, stumps, or outbuildings.
Culex tarsalis is probably the main carrier of West Nile Virus because of its affinity to take blood meals
from birds. At least 120 bird species and eight mammal species have been infected (USGS 2002).
Corvids (crows, magpies, ravens, and jays) seem to be affected more than other species; however,
because many corvids die when infected, they are not an ideal host for the virus. Other species, such as
house spanows, do not seem to die as readily when infected and are therefore a more effective host for
the virus.
The highest risk of infection for humans is August through early September. The incubation period for
the virus is 3 to 14 days in humans.
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3.0 General Overview of Mosquito Habitat and
Figure 3-1 Mosquito Life Cycle
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4.0 METHODS AND MATERIALS FOR LARVAL MOSQUITO
CONTROL
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Control efforts conducted during the larval stage of mosquito development are the most effective and
environmentally sound way to eliminate target mosquito species and, therefore, to most effectively reduce
the risk of human WNV infection. The U.S. Environmental Protection Agency's (EPA) Office of
Pesticide Programs is responsible for ensuring that a pesticide will not pose unreasonable adverse effects
to human health and the environment. To prevent and minimize the impacts of pesticides on fish, wildlife
and plants, the U.S. Fish and Wildlife Service provides technical assistance and consults with the EPA
during registration and reregistration of pesticides. In Colorado, pesticide rules and regulations are
administered and enforced by the Colorado Department of Agriculture, Division of Plant Industry.
4.1 PREFERRED LARVAL CONTROL AGENTS
Larval control agents (larvicides) are materials that target the larval stage of the insect and prevent
mosquitoes from becoming breeding, biting, disease carrying adults. The preferred larval control agent
proposed for use under this plan is the microbial insecticide Bacillus thuringiensis israelensis, or Bti.
This product is discussed below.
4.1.1. Application of Bacillus thuringiensis israelensis
Bti is a microbial insecticide formulated for use to control mosquito larvae in aquatic habitats. The
product is manufactured as corncob granules and is applied using hand-held seeders. Bti is a naturally
occurring bacterium in soil that produces poisons that cause disruption of bodily functions in insects. The
poisons are produced as protein crystals during formation of spores, which is a process that allows the
bacterium to survive under adverse conditions (ET'N 1996), When they are ingested by insects, the
protein crystals dissolve in response to intestinal conditions of suscepYible insect larvae. The cells in the
gut become paralyzed, interfering with normal digestion and triggering the insect to stop feeding (ETN
2003).
The application of Bti for larval mosquito control is desirable for several reasons. First, it lasts only 24
hours in water (EPA 1998 and 2002; ET'N 2003; NPTN 2000). Bti will undergo rapid inactivation during
exposure to UV light. Second, it does not affect nontarget vertebrate species, such as fish (EPA 1998 and
2002; ETN 2003; NPT'N 2000). Third, the bacterium kills the mosquito ]arvae, and field technicians can
see results the same day the Bti is applied. A negarive effect is that part of the food chain is temporarily
removed by killing the larvae, potentially affecting predators by removing a source of food. However, it
is not 100 percent effective (MMCD 2002), so the entire food chain is not completely broken, and
predators would not likely be negatively affected.
The application of Bti is the preferred method for larva] mosquito control because it serves the greatest
public need. The threat that WNV will infect residents of Boulder outweighs the minimal impacts of this
bacterium on the areas where it is used. Larval treatments must occur to contain and minimize the threat
of WNV infection in humans. Adverse impacts to wetlands will be minimized by applying Bti at
recommended concentrations, and all treatment areas will be posted with signs before Bti is applied. The
Material Safety Data Sheet (MSDS) for Bti can be found in Appendix B. Proper handling of Bti and
application requirements are described in the field manual (Greystone 2003) proposed for use under this
plan.
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4.0 Methods and Materials for Larval Mosquito Control
4.2 OPTIONAL METHODS AND MATERIALS FOR LARVAL
MOSQUITO CONTROL
Two optional larval control techniques are not prafened, but were also not rejected as options. These
options include the insecticide Bacillus sphaericus and mosquito habitat manipulation. These methods
are discussed below.
4.2.1. Application of Bacillus sphaericus
Bacillus sphaericus (Bs) is a naturally occurring bacterium in soil that produces protein crystals with
larvicida] activity similar to Bti. The toxin is active only against the feeding larval stages and must be
partially digested before it becomes activated. Bs adversely affects larval stages of insect species in the
Order Diptera, Suborder Nematocera, Family Culicidae (mosquitoes).(FCCMC 1998). Bs is specific in
causing mortality to mosquito larvae; Culex species are the most sensitive to Bs. In contrast to Bti, Bs is
virtually non-toxic to black flies (FCCMC 1998). Mammals and other non-target species are unaffected
by applications of Bs.
The application of Bs is an option for control of WNV, but is not proposed for use under this plan. It is
similar to Bti in that it is a bacterium, but the differences are significant. Bs is desirable because, like Bti,
it kills the mosquito larvae, and field technicians can see results the same day the bacterium is applied. Bs
also has demonstrated efficacy in controlling mosquito larvae in highly organic aquatic environments,
including sewage-waste lagoons and septic ditches (FCCMC 1998). Certain factars make this product
undesirable for use in the City of Boulder, however, First, the residual bacteria remain in water for 2 to 4
weeks (FCCMC 1998). Second, mosquitoes have been shown to develop resistance, which reduces its
effectiveness (Nielsen-LeRoux and Silva-Filha 2003). Finally, part of the food chain is temporarily
removed, potentially affecting predators by removing a source of food.
4.2.2. Mosquito Habitat Manipulation
Manipulation of mosquito habitat in wetlands is another option for control of WNV. Manipulation
involves water management strategies to eliminate mosquito breeding areas and can include activities
such as filling in or improving drainage in certain areas, or pumping water out of low-]ying areas.
Manipulation can permanently change the function of the mosquito habitat and can severely affect the
ecological integrity of the wetland ecosystem. This method of mosquito ]arvae conhol would be
implemented only on non-regulated wetlands under this plan.
4.3 METHODS AND MATERIALS CONSIDERED BUT NOT
RECOMMENDED FOR LARVAL MOSQUITO CONTROL
Three optional larval control techniques were considered for use in this plan but are not recommended.
These options include the insecticide methoprene, predatory fish, and the use of oils. These methods are
discussed below.
4.3.1. Application of Methoprene
Methoprene is an insect growth regulator that interferes with the maturation phase It causes mosquito
larvae to continue Yheir larval development rather than molting into a pupa or an adult (ETN 2003).
Methoprene is different from Bti because it is a hormone, and not a bacterium, and it does not
immediately kill the mosquito larvae (EPA 2002).
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4.0 Methods arid Materials for Larval
The application of inethoprene is an option for WNV control, but its use is not recommended as part of
this plan. Methoprene is effective because it prevents the larvae from becoming breeding, biting adults.
It does not kill the larvae so the food chain remains intact and there are no effects on predators. However,
it is undesirable because the mosquito larvae are not killed, and therefore, the efficacy of the treatment
cannot be observed in the field. The inability of field technicians to immediately see results is
undesirable. If a larvae population is treated that is positive for WNV and treahnent is not effective,
adults will emerge and can spread WNV. With Bti, field technicians can verify that the treatment was
effective within 24 hours and can reapply the larvicide if it was not effective. Additionally, the
persistence of inethoprene in the environment is prolonged, since most of the products that contain
methoprene are manufactured as slow-release formulas. Methoprene is only 56 percent successful (it kills
only 56 percent of mosquito larvae) when it is applied at the rate of 2.5 ]bs/acre (MMCD 2002). It can
also affect more nontarget species than does Bti, including fish and aquatic invertebrates. Finally,
ultraviolet rays from the sun also tend to break down methoprene, reducing its effectiveness (EPA 2003).
Because Colorado has a very high number of sunny days in the summer, it is not the best product to use
under this plan.
4.3.2. Introduction of Predatory Fish
The biological control of mosquitoes often includes introduction of top-water feeding minnows such as
Gambusia affinis (mosquito fish). These predatory fish are not native to Colorado, and introduction of
this species into a wetland habitat can be detrimental to native species. It can severely affect richness and
evenness of native species and can quickly dilute local genetic adaptations, resulting in a pond populated
by mosquito fish and little else.
4.3.3. Application of Oils
The application of oils to water is another option for the control of mosquito larvae but is not proposed for
use under this plan. The application of oils to water is undesirable because the oils are not species-
specific (EPA 2002). The oi] will kili any organism that lives near the surface and that depends on a
breathing tube. Wetland function could be severely affected by this option.
4.4 SURVEILLANCE OF LARVAL MOSQUITOES
4.4.1. Objective
The objective of the plan is to monitor the seasonality and abundance of mosquito populations and detect
larvae of Culex tarsalis and Culex pipiens within regulated wetlands on City of Boulder lands.
4.4.2. Background
Currently, the two species of mosquitoes that threaten people with transmission of WNV in the State of
Colorado are Culex tarsalis and Culex pipiens. In addition, WNV has been found in many other species
of mosquitoes in the United States. Although these species are not a threat at this time, plans should be in
place to deal with any that may become a transmitter of WNV. The Colorado Department of Public
Health and Environment (CDPHE), Animal Control, and the Centers for Disease Control and Prevention
will be the main source for information on other possible threats. Regular coordination with the CDPHE
and Animal Control will be conducted to share new information on WNV in the area.
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4.0 Methods and Ma[erials for tarval Mosquito Control
The risk of mosquito-bome disease depends on the number of mosquitoes capable of transmitting the
virus, the prevalence of the virus among them, and the populatioo density of people in the area. Proper
surveillance data on larval mosquitoes are important in guiding prevention and control. Surveillance on
larvae can provide information on the expected abundance of adult mosquitoes and can indicate areas
where efforts to eliminate mosquitoes at the source should be targeted.
4.4.3. Activities Planned
• Greystone will continue to work closely with city agencies to collect and map information on
potential breeding habitats for mosquitoes.
• Greystone will identify the areas that should be regularly inspected for the presence of larvae.
These sites will routinely inspected to assess the presence of Culer tarsalis or Culex pipiens
larvae.
• Information on larval habitat will be collected and updated throughout the season.
• Larval species will be identified and updated throughout the season.
• Greystone will recommend control of mosquito larvae if Culex tarsalis or Culex pipiens are
present in any breeding habitat.
• Greystone will continue to work closely with city agencies to identify the best control measures
for each breeding habitat and situation.
These activities for surveillance of larval mosquitoes are displayed graphically in Figure 4-1.
4.5 CONTROL OF LARVAL MOSQUITOES
4.5.1. Objective
The objective of the plan is to reduce the abundance of adult Culex tarsalis and Culex pipiens mosquitoes
using Integrated Mosquito Management (IMM) practices. Ultimately, the objective is to reduce the threat
of WNV for the residents of the City of Boulder.
4.5.2. Background
All mosquitoes begin life in the water. Culex pipiens, an enzootic vector of WNV, breeds quickly and
uses standing water that contains decaying organic materials to lay their eggs. Prime breeding sites
include discarded tires left outdoors, poorly maintained bird baths, clogged rain gutters, unused
swimming and plastic wading pools, pots and pans that contain standing water, and holes in trees.
Although it is rare, Culex pipiens may be found in puddles of water that contain organic materials in
Colorado as in some other parts of the country. Eliminating breeding sites is the simplest and most
effective way to reduce the population of Culex pipiens. Every owner of residential and commercial
property should regularly inspect the property and buildings to evaluate and eliminate conditions that may
enable mosquitoes to breed.
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4.0 Methods and Matenals for Larval Mosquiro Control
Figure 4-1 Larval Surveillance Flowchart
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4.0 Methods and Ma[erials for Larval Mosqui~o Control
Culex tarsalis, the other enzootic vector of WNV, breeds quickly and uses standing or slow-moving water
with a wide range of habitats to lay eggs. Mosquito breeding can be prevented by either eliminating the
standing water (source reduction) or, if that is not possible, by treating the water with larvicide to prevent
mosquitoes from developing.
Greystone's public education campaign emphasizes the need for Boulder residents to eliminate mosquito-
breeding sites around homes and to practice personal protection. This plan will include working with city
officials to develop a website and a hotline for residents to contact.
Greystone will apply larvicides in acwrdance with regulations set forth by the City of Boulder and other
governing bodies. Recommendations for applying larvicide will be provided to city officials and will
include the type and amount of material to be used on a case-by-case basis. Larvicides will be applied by
ground crews where deemed necessary. Cunently, there is no plan to apply larvicide with aerial
equipment. Larvae will be collected after treatment to evaluate the efficacy of control operations.
Greystone recommends the use of the larvicide VectoBac (Bacillus thuringiensis var, israelensis, or Bti),
with VectoLex (Bacillus sphaericus or Bs) as options in areas where the water is polluted and contains a
much higher amount of organic materiaL These products are considered ideal for mosquito management
because they are specific to mosquitoes and they lack toxicity to humans or the natural enemies of
mosquito larvae. These bacteria form asexual reproductive cells, called spores, that enable them to
survive in adverse conditions. They also produce unique crystalline bodies. When they are eaten, the
crystalline bodies dissolve in the intestine of the larvae and paralyze the cells in the gut, interfering with
normal digestion and causing tke larvae to stop feeding. The spores can then invade other tissues,
multiplying in the larva's blood, unYil the insect dies. Deatb typically occurs within a few hours of
ingestion. Altosid (methoprene) is an insect growth regulator that interferes with the development cycle
of mosquitoes and other aquatic dipterans. By their nature, it is more difficult to measure the efficacy of
methoprene than of Bs or Bti because of the faster action of the bacteria.
4.5.3. Planned Activities
• Greystone will continue to work closely with city agencies to collect and map information on
potential breeding habitats for mosquitoes.
• Greystone will advise the City of Boulder of mosquito breeding sites that can be eliminated, for
example, areas of standing water associated with surface grading problems, road construction,
clogged catch basins, or obshucted waterways. These water bodies do not fit the criteria of
wetlands set forth by the City of Boulder Public Works Deparhnent.
• Information on larval habitat and efficacy of control materials will be wllected and updated
throughoutthe season.
• Greystone will advise the City of Boulder when larvicides should be applied in specific mosquito
habitats.
• Greystone will oversee or undertake larval control operations with the approval of city officials
on a case-by-case basis. See the flow chart on larval control.
• Greystone will provide Boulder officials with updated maps of lmown mosquito habitats to
facilitate communication of larval control in a timely manner.
Preliminary DraR Mosquito Plan 4-21-03 Final.doc Agenda Item # ~/7 Page # r~~~
4.0 Methods and Materials for larval Mosquito Control
• Greystone will assist the City of Boulder with a comprehensive public information campaign.
When an infected mosquito, bird, or mammal is identified in the area, Greystone staff will
intensify larval surveillance and control. Public outreach should be expanded in targeted
neighborhoods on elimination of breeding sites and personal protection.
4.5.4. Larval Mosquito Control Thresholds
Developing thresholds to reduce mosquito annoyance is a well-documented and easily attainable goal.
Developing thresholds to solely control disease vectors requires significantly more effort. There are no
established thresholds for controlling disease vectors in mosquitoes in the United States. Acwrding to
Joseph Conlin, Technical Advisor for the American Mosquito Control Association, various agencies have
tried different approaches resulting in no evidence that any one procedure works more efficiently than the
other.
Most health departments and mosquito control agencies agree that an extensive larval control program is
the best defense against an arbovirus such as West Nile virus (John Pape 2003). Larval control can be
approached in various fashions. For example, the CMC uses their threshold for pest mosquitoes as their
threshold for disease vectors (Mike McGinnis and Michael Doyle, Personal communication, March
2003). The CMC does not identify specific species (disease vectors) to initiate larval control but, they do
have a numerical threshold of human biting mosquito species to initiate larval conhol relating to pest
management. Therefore, CMC's approach to larval control concerning Greystone's targeted species
(Culex tarsalis and Culex pipiens) can be very effective. However, this approach is more efficient in
controlling all species of mosquito larvae and not concentrated on controlling specific vector mosquito
species such as C. tarsalis and C. pipiens. Greystone's approach to larval control will be to identify
Culex tarsalis and Culex pipiens before initiating control efforts. The method will allow pest mosquitoes
and non-biting mosquitoes to persist in the environment. The approach requires significantly more
surveillance as opposed to control. In comparison, it is irrelevant which of the two approaches will
control more effectively Culex tarsalis and Culex pipiens, but it is certain that Greystone's initial
approach will involve the use of less control materials and be focused only on the targeted vector species.
Greystone's field staff is trained to properly identify Culex tarsalis and Culex pipiens larvae, both in the
field and in the lab; however, proper identification of the mosquitoes to the species level is intensive and
could possibly hamper control efforts. Greystone's competent lab technicians will make every effort to
expedite the process and eliminate delays. If the threat of WNV increases or the identification process of
Culex tarsalis and Culex pipiens species slows larval control efforts to such a degree that excessive larvae
are being allowed to hatch into adults, Greystone wil] recommend that control measures switch focus.
Larvae contro] would be more quickly implanted if ]arvae are identified to the genus level only to avoid
the delays caused by identifying larvae to the species level. The Culex genus is easily identifiable in the
lab and also in the field during all four instars, or ]arva life stages, allowing quicker tumaround time for
the control process This procedure will allow our field staff to perform conrtol once they have identified
mosquitoes to the genus level. A larval sample will still be collected and brought to the lab for
confirmation. This will be an ongoing process throughout the season, as the threat of WNV increases.
4.5.5. Planned Activities for Larval Thresholds
Greystone will recommend control of mosquito larvae if Culex tarsalis or Culex pipiens are
present in any breeding habitat. (See "Control of Larval Mosquitoes")
• Greystone staff will intensify larval surveillance and control when large numbers of adult female
Preliminary DraR Mosquito Ylan 4-21-03 ~inal.doc Agenda Item #_.SA Page # a? ~
4.0 Methads and Materials for larvel Mosquiro Control
Culex tarsalis and Culex pipiens are found. This may include a recommendation to control Culex
mosquitoes for more efficient larval control efforts.
• Greystone staff will intensify larval surveillance and conirol when an infected mosquito, bird, or
mamma] is identified in the area. This may include a recommendation to control Culex
mosquitoes for more efficient larval contro] efforts.
• Greystone will identify areas that should be regularly inspected for the presence of mosquito
larvae and adults. These sites will be routinely inspected to assess the presence of Culex tarsalis
and Culex pipiens larvae and adults.
• Information on larval and adult mosquito habitat wil] be collected, updated, and evaluated
throughoutthe season.
• Greystone's recommendations will be communicated to the City of Boulder and other governing
agencies. When they are approved by the city, a press release will be drafred to notify the public
of the recent findings.
These activities for control of larval mosquitoes are displayed graphically in Figure 4-2.
Agenda Item # S ~} Page # ; ~J~
Preliminary DraR Mosquito Plan 4-21-03 Final.doc
4.0 Me[hods and Materials for Larval Mosaui[o Control
Figure 4-2 Larval Mosquito Control Flowchart
Agenda Item # .~ Page # „?_5
Preliminary Drafl Mosqui[o Plan 4-21-03 FinaLdoc
5.0 METHODS AND MATERIALS FOR ADULT MOSQUITO
CONTROL
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Adult control agents (adulticides) are materials applied for control of adult mosquitoes. Control of adult
mosquitoes is not proposed as part of this plan, but rather is included as a contingency measure if
surveillance suggests that the level of WNV activity poses a significant threat to human health. The
products that would be used in this event are discussed below.
5.1 ADULT CONTROL AGENTS
The adulticides recommended for application under the adult mosquito control contingency plan are
lmown as synthetic pyrethroids. Synthetic pyrethroids are synthesized derivatives of natwally occurring
pyrethrins, which are taken from pyrethrum, the olearesin extract of dried chrysanthemum flowers. The
three specific pyrethroids that could be implemented as a contingency measure for adult mosquito.control
are permethrin, resmethrin, and sumithrin.
These products cause rapid laiockdown of adult mosquitoes. They exhibit low mammalian toxicity,
degrade rapidly in sunlight, leave little or no residue, and do not bioaccumulate in the environment.
Pyrethroids are extremely toxic to aquatic organisms; however, dosage rates control the toxicity of these
products to non-target species. Lobster, shrimp, mayfly nymphs, and zooplankton are the most
susceptible non-target aquatic organisms (Mueller-Beilschmidt 1990).
5.1.1. Application of Permethrin
Permethrin is effective against all stages of insect growth. Compared with other pyrethroids, permethrin
is stable, even when exposed to ultraviolet light. Permethrin is strongly absorbed to soil and other organic
particles; however, it is degraded by sunlight in water and on soil. Permethrin has been found to be
highly toxic to fish in ]aboratory experiments, but poses little risk to aquatic life when applied according
to label directions (NPTN 1997).
5.1.2. Application of Resmethrin
Resmethrin is a synthetic pyrethroid used as an insecticide for mosquito control. Resmethrin is
considered extremely toxic to fish, other aquatic life, and bees (ET'N 1993). This product breaks down
rapidly in the presence of light and humidity.
5.1.3. Application of Sumithrin
Sumithrin has been registered for use since 1975. It is used for ultra-low volume (ULV) applications to
control adult mosquitoes. Sumithrin is slightly toxic but degrades rapidly in aquatic environments under
dry, sunny conditions.
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5.0 Methods and Materials for Adult Mosquito Control
5.2 SURVEILLANCE OF ADULT MOSQUITOES
5.2.1. Objective
The objective of the plan is to monitor the seasonality and abundance of adult mosquitoes to
detect the presence of Culex tarsalis and Culex pipiens in the City of Boulder and to reduce the
threat of WNV.
5.2.2. Background
The risk of WNV depends on the number of mosquitoes capable of transmitting the virus, the prevalence
of the virus among them, the frequency with which C. tarsalis and C. pipiens transmits WNV to
mammalian species, and the population density of people in the area. Proper surveillance data on adult
mosquitoes, infected birds, and infected mammals is important in guiding prevention and control.
Surveillance of adult mosquitoes, which includes testing for the presence of WNV, can provide
information on the potential threat to residents and can indicate areas where efforts to eliminate
mosquitoes should be targeted. Much of this information will be gathered from contacting CDPHE and
Animal Control on a regular basis.
A continued and extensive communication network will continue to serve as the best resource to make the
most informed decisions on surveillance and control of WNV. This network will involve city agencies,
the Colorado Department of Public Health and Environment, the Centers for Disease Control and
Prevention, the Boulder County Depariment of Health, the Boulder County Mosquito Control District,
Colorado universities, regulatory agencies, and other bodies associated with surveillance of WNV.
5.2.3. Activities Planned
• Greystone will continue to work closely with city agencies to collect and map
information on potential locations of mosquito harborage.
• Greystone will identify the areas that should be regularly inspected for the presence of
adult C. tarsalis and C. pipiens mosquitoes. These sites will be subjected to routine
collections to evaluate the presence of mosquitoes infected by WNV.
• Information on adult harborage will be collected and updated throughout the season.
• Adult mosquitoes will be collected using carbon dioxide-baited CDC light traps, gravid
traps, and sweep nets on a biweekly basis.
• Adult species will be identified and updated throughout the season.
• Adult collections will be tested for WNV throughout the season.
• Communication lines with health departments and animal control officials will be
maintained to remain informed of any dead birds or mammals that are coilected and
tested for WNV. '
Preliminary Draft Mosquito Vlan 4-21-03 Final.doc Agenda Item #. Sft Page #.~
5.0 Methods and Ma~eriais for Adult Mosuuito Control
• Adult mosquito collections will be expanded in areas where WNV is detected in
mosquitoes, birds, other animals, and humans. These collections will help define a zone
of potential local transmission and guide intervention.
• In the event WNV is found in adult mosquito collections, Greystone will recommend to
the City of Boulder that adult mosquito control efforts begin.
• Greystone will continue to work with the City of Boulder to identify the best control
measures for each harborage location and situation throughout the season.
• In the event that pesticides are applied for control of adult mosquitoes, Greystone will
collect specimens more frequently to evaluate the efficacy of the control measures.
These activities for surveillance of adult mosquitoes are displayed graphically in Figure 5-1.
Agenda Item # ,~ Page # ~~
Preliminary DraR Mosyuito Plan 4-2L03 Final.doc
5.0 Methods and Materials for Adult Mosquito Control
Figure 5-1 Adult Surveillance Flowchart
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5.0 Methods and Materials for Adult Mosquiro Control
5.3 CONTROL OF ADULT MOSQUITOES
5.3.1. Background
Responsible IMM practices include extensive larval control with a contingency plan for adults.
Theoretically, the ideal larval control plan would eliminate the need for any control of adults. However,
the rapid development of mosquitoes from egg to adult and the persistent nature of breeding in an
extensive variety of stagnant waterbodies make complete elimination impossible. The flight of C. tarsalis
can range as far as 20 miles. Although it is rare far C. tarsalis tq fly 20 miles, it is possible that
mosquitoes outside the city limits would migrate into Boulder. Therefore, a plan for control of adults is
necessary as a contingency.
The adulticides Greystone recommends are ]rnown as synthetic'pyrethroids. The three specific
pyrethroids are permethrin, resmethrin, and sumithrin. These products are first-generation synthetic
pyrethroids that have been used for more than 30 years. All three products cause rapid lmockdown of
adult mosquitoes. They exhibit low mammalian toxicity, degrade rapidly in sunlight, leave little or no
residue, and do not bioaccumulate in the environment. Dosage rates control the toxicity of a product non-
target species. Dosage rates can be low to control mosquitoes. These products are applied in small
quantities per acre, referred to as ULV application. ULV delivery techniques minimize environmental
impacts at the same time they effectively manage populations of adult mosquitoes. Greystone will
monitar the application of the adulticide to ensure compliance with all regulations and requirements
promulgated by the EPA, State of Colorado, and City of Boulder.
The presence of mosquito-borne pathogens in Boulder, if detected, will prompt one or more responses or
interventions. These interventions can range from continuing existing routine surveillance to, in worst-
case scenarios, large-scale ground application of adulticides. Greystone will use the surveillance data to
assess the risk of an outbreak of human disease and the need to apply pesticides in a limited and targeted
area to control adult mosquitoes. The assessment will consider habitat; time of year; weather conditions;
the level of documented virus; the distribution, density, species, age, and infection rate of the vector
population; and the density and proximity of human populations to the vectors.
The response of Greystone and the City of Boulder will depend on, but will not be limited to, the intensity
and persistence of the pathogen activity, the proximity of pathogen activity to human populations within
the ciTy, the time of year, the population density of the vector, and weather conditions. Because these
conditions vary greatly and cannot be predicted, a consultation process will be used to identify the
responses that are appropriate, if any, on a case-by-case basis. The responses can be grouped into three
broad categories or levels of risk, depending on the level of pathogens detected.
5.3.2. Activities Planned
Level 1- No Pathogen Detected
Greystone will continue surveillance and control programs as outlined in this plan. Periodic
reports or communications will be provided to the City of Boulder to describe the status of the
various surveillance programs. The city may issue periodic press releases to provide the public
with the current results of surveillance.
Level 2- Initial or Sinele PathoRen Detected
Initial or a single detection of mosquito-borne pathogens in mosquito or avian pqpulations in
Boulder will prompt a move to Leve12 responses.
Preliminary DraIl Mosquito Plan 4-21-03 Final.doc Agenda Item # .?/ / Page # ~,
5.0 Methods and Materials for Adult Mosquito Control
Greystone's recommendations will be communicated to the City of Boulder and other governing
agencies. When they are approved by the city, a press release will be drafted to notify the public
of the recent findings. Surveillance will continue with the following added activities:
- Adult mosquito trapping will begin in the area of concern if additional surveillance data are
required.
- Larval surveillance will be enhanced in affected areas if needed.
- Laboratory testing of adult mosquitoes will be a priority in affected areas.
- Data from these additional collections will aid in evaluating the extent of pathogen
transmission and mosquito populations and be used to guide control measures, if applicable.
• Level 3- Continued or Multple Pathoeen Detections
Persistent detection of mosquito-bome pathogens or detection in bridge vector mosquitoes (C.
tarsalis or C. pipiens) or in non-avian vertebrate populations in the City of Boulder will prompt a
move to Level 3 responses.
Greystone's recommendations will be communicated to the City of Boulder and other governing
agencies. When they are approved by the city, a press release will be drafted to notify the public
of the recent findings. Surveillance will continue as noted above, and control measures will be
implemented.
- Adult mosquito trapping will begin in the area of concern if additional surveillance data are
required.
- Larval surveillance will be enhanced in affected areas if needed.
- Laboratory testing of mosquito pools will be a priority in affecfed areas.
- Control measures wil] be considered:
/ Application of ]arvicides to areas where large numbers of mosquitoes breed
/ Ground application of adulticides to immediate areas of concern.
/ Application by truck-mounted fogger of adulticides to broader areas, based on
surveillance data.
/ Restrictions on or cancellation of outdoor evening activities.
/ Recommendation to close recreational areas.
In addition, Greystone will recommend that the city draft an additional mailing to the public of
recent findings and protective measures they should take.
- Greystone will monitor the efficacy of the adulticides.
Preliminary DraIl Mosquito Plan 4-21-03 Final.doc Agenda Item #,~ Page. #~
5.0 Methods and Materials for Adult Mosqui[o Control
- Greystone will consider EPA-registered products for mosquito control that contain the
following active ingredients: resmethrin, permethrin and sumithrin. Greystone will review all
of the available information on the health impact of pesticides. Any products used will be
applied in compliance with city, state, and federal laws and regulations.
- The public will be notified o£ the schedules for application of adulticide in advance, which
will allow time to take any necessary precautions to reduce exposure to the pesticide.
- Hospitals will be notified of the schedule for application of adulticides. Information on the
pesticides that will be used will be provided to the public and to physicians and other health
care providers.
- Before control of adult mosquitoes begins, information on pesticides and their possible
adverse health effects will be delivered to all hospital emergency departments, including
product information on pesticides, Material Safety Data Sheets, and other information relevant
to identifying possible exposure to pesticides. Calls received by the Colorado Poison Control
Center will continue to be monitored during pesticide spraying and will be forwarded to the
Colorado Registry for Pesticide Sensitive People for possible follow-up and inclusion in the
regisiry.
- For quality assurance, Greystone will provide guidance on and assist with the technical
elements of pesticide application so that operations are conducted according to plan and comply
with applicable regulations.
- Adult mosquito control will occur during the day with hand-held spray units and in the
evening when mosquitoes are most active with hand-held spray units and truck-mounted fogger
units.
- Information will be distributed at least 24 hours in advance through the media, Greystone's
website, and pertinent city and community organizations.
Y Greystone will monitor and assess control measures for any potential environmental and
health effects through several means, including pre- and post-spray environmental sampling and
complaints of exposure to pesticides received by Greystone.
- Depending on the findings from surveillance and other criteria, Greystone may direct the
application of adulticides in response to community concems.
5.3.3. Adult Mosquito Control Thresholds
Adult control thresholds for disease vectors are much harder to establish and justify compared to larval
thresholds. Since the adult mosquito is no longer in a contained aquatic environment, adult control is not
nearly as effective. Adult mosquitoes will often vacate an area until the adulticide evaporates or settles to
the ground. Adulticides also have more impact on non-target organisms compared to larvacides. Adult
control activities that include spraying of pesticides will be the final alternative that Greystone would
recommend pursuingin an attempt to reduce the threat of WNV. Spraying of pesticides in an urban
environment is the most costly, inefficient, and environmentally unfriendly procedure in an Integrated
Mosquito Management (IMM) program.
Greystone's final recommendation on adult control activities will weigh heavily on recommendations
PrcliminaryDraRMosquitoPlan4-21-03Pinal.doc AgendaItem# _`~f1 Page# c7,~
5.0 Methods and Ma[enais for Adult Mosquito Control
from the Centers for Disease Control and Prevention, the Colorado Deparhnent of Health and
Environment, the Boulder County Department of Health, the City of Boulder, and other governing
agencies. The threshold established by Greystone for implementation of adult mosquito control activities
is if WNV is found to be present in Culex tarsalis and Culex pipiens adult females. This does not mean
that Greystone recommends spraying pesticides every time WNV is discovered in adult mosquitoes. A
detailed process is outlined in our "Control of Adult Mosquitoes" section.
5.3.4. Assessment and Summary
Dosage rates contro] the toxicity of a product to non-target species. As a result, dosage rates can be very
low to control mosquitoes. These products are applied in small quantities per acre, called ULV
application. ULV delivery techniques minimize environmental impacts while effectively managing adult
mosquito populations. Greystone will monitor applications of adulticides to ensure compliance with all
regulations and requirements promulgated by the EPA, the State of Colorado, and the City of Boulder.
5.3.5. Planned Activities for Adult Mosquito Thresholds
• Greystone will continue to work closely with city agencies to collect and map information on
potential breeding habitats and harborage locations for mosquitoes.
• Greystone will send samples of adult female Culex tarsalis and Culex pipiens to the lab for WNV
testing.
• Greystone will intensify adult mosquito surveillance if adult female Culex tarsalis or Culex
pipiens are tested positive for WNV. Data from these additional collections will aid in evaluating
the extent of pathogen transmission and mosquito populations and be used to guide control
measures, if applicable.
• Greystone will recommend adult mosquito contro] activities take place if additional samples of
the mosquito collections are infected with WNV. (See "Control of Adult Mosquitoes")
• Greystone will recommend adult mosquito control activities take place when an infected bird or
mammal is identified in the area. (See "Control of Adult Mosquitoes")
• Greystone will identify areas that should be regularly inspected for the presence of mosquito
]arvae and adults. These sites will be routinely inspected to assess the presence of Culex tarsalis
and Culex pipiens larvae and adults.
• Information on larva] and adult mosquito habitat will be collected, updated, and evaluated
throughoutthe season.
• Research on thresholds for disease vectors will continue throughoutthe season.
• Greystone's recommendations will be communicated to the City of Boulder and other governing
agencies. When they are approved by the city, a press release will be drafred to notify the public
of the recent findings.
These activities for control of adult mosquitoes are displayed graphically in Figure 5-2. ,
Preliminary Draf[ Mosqui[o Poan 4-21-03 Final.doc Ab7ep(ia ltQ[p # ,~ pBgC #~~~)
5.0 Methods and Materials for Adult
Figure 5-2 Adult Mosquito Control Flowchart
Agenda Item #~ Page # , ~
Prcliminary Dratl Mosyuito Plan 4-21-03 Final.doc
5.0 Methods and Ma[erials for Adult Mosquito Con[rol
5.3.6. Assessment and Summary
Dosage rates control the toxicity of a product to non-target species. As a result, dosage rates can be low
to control mosquitoes. These products are applied in small quantities per acre, called ULV application.
ULV delivery techniques minimize environmental impacts while effectively managing adult mosquito
populations. Greystone will monitor applications of adulticides to ensure compliance with all regulations
and requirements promulgated by the EPA, the State of Colorado, and the City of Boulder.
Agenda Item # `~ A Page #,3 5
Preliminary Draft Mosquito Plan 4-21-03 FinaLdoc
6.0 POTENTIAL IMPACTS OF BT/TO NONTARGET
SPECIES
ec.aava.:,: a ~.~.:ax•~?,:zur-;ra*:~;;v:~a~a,..,a; ..~;=;m.a~ _ ~e . , ... > ^~uxs~:~ur.us» .... ~~rxsa~~~mtrrxr+ra;wuc~~c>aar:~r:~~~=_
The bacterium Bti has been studied and in use as a mosquito larvicide for about 20 years. Hundreds of
peer-reviewed scientific joumal articles and government agency documents have been published about
the potential for ecological effects from Bti. It appears, based on a review of several summary
publications from reputable federal agencies, that Bti is non-toxic to nearly all types of non-target
organisms (in other words, the target organisms for Bti are mosquitoes and black flies), including other
insects, with two exceptions. Bti is toxic to microorganisms in soil (such as nematodes) and may be toxic
to Daphnia (a genus of freshwater invertebrate crustacean), according to the EPA and Agriculture and
Agri-Food Canada. This information is summarized in Table 6-1.
However, most of the studies cited by the govemment summary documents were conducted in the
laboratory for a short duration and considered only the effects to the study organisms themselves. Two
studies published in 1998 provide contrasting evidence of more wide-ranging effects to non-target
species. One of these studies (FCCMC 1998) concluded that, although Bti is highly effective in killing
the targeted mosquito larvae (C. tarsalis and C. pipiens), it is also lethal to many other insect species in
several taxonomic orders besides Diptera (flies). Some larval mortality of insect species that are normally
associated with mosquito larvae in aquatic habitats was observed in the Families Chironomidae (midges),
Ceratopogonidae (biting midges), and Dixidae (dixid midges). However, the conceniration of Bti
required to cause this effect was 10 to 1,000 times higher than normal application rates for mosquito
control. In another study (Hershey et al. 1998, see Table 6.1) of Bti applied for 3 years at normal rates Yo
27 wetlands, adverse impacts to insect and non-insect orders were delayed until the second year of
application. In the second and third years of application, significant reductions in insect abundance and
insect species richness were observed. Overall insect community composition was radically altered, and
the authors speculated that many species were adversely affected indirectly via changes to the ecosystem
structure. The authors also estimated that wetland function had been disrupted and degraded, likely
causing indirect effects to wetland vertebrates that could not be measured in the 3-year timespan.
Agenda Item # _~~ Page # -~~
Prcliminary Drafl Mosquito Plan 4-21-03 Pinal.doc
6.0 Pocential Impacts oCBti m
TABLE 6-1: LITERATURE REVIEW OF TOXIC EFFECTS FROM BAC/LLUS
THUR/NG/ENS/S SUBSPECIES /SRAELENS/SON NON-TARGET ORGANISMS
Agency/Source Non-target Effects Comments
Organism '
EPA Office of Pesticide Small laboratory No unacceptable acute Based on standard acute testing
Programs~ mammals (rat, rabbit) toxic effects via inhalatioq dermal exposure,
and eye irritation
EPA Office of Pesticide
Human infants & Prediction included l Ox margin
~
Programs~ children No toxicity of safery and special exposure
pattems.
EPA Of£ice of Pesticide
Pro
rams~
Humans No endocrine or
immune system No evidence known to exist by
th
EPA
g
effects e
.
EPA Office of Pesticide Birds (mallard, Based on standard acute and
Programs~ bobwhite quail) No toxicity subacute testing.
Green lace-wings-16 day LCso
> I.5 x 10a colony-forming units
Insects (green lace-wing (cfu)/g diet; 16 day no-observed4
EPA Office of Pesticide larvae, parasitic wasps, effects-level (NOEL) = 2.5 x 10
Programs~ predaceous water Little to no toxicity cfu/g diet. 7
beetles) Wasps-30 day LCSo > 7.9 x 10
cfu/g diet.
Water beetles-9 day LCso > 1.8
x 108 cfu/g diet.
EPA Office of Pesticide
Programs~ Honey bee Minimal toxicity
5 day LCso > 7A x 10' cfu/g diet.
Trout-aqueous LCSO > 8.7 x 109
cfu/l and oral LCso > 1.7 x 1010
cfu/g food, slightly toxic;
aqueous LCso > 1.4 x 10~0 cfu/1
EPA Office of Pesticide and oral LCso > 53 x 10' cfu/g
Programs~ Fish (trout, bluegill) No toxicity food.
Bluegill- aqueous LCso > 8.9 x
10' cfu/I water and oral LCSo >
13 x 1010 cfu/g food; aqueous
LCso > 1.6 x 1010 cfWl and oral
LCSO > 4.3 x 109 cfu/g food.
EPA Office of Pesticide
Programs~ Freshwater
invertebrates (Daphnia)
Modera[ely roxic
21 day LCso = 5-50 ppm.
EPA Office of Pesticide Plants (tenestrial, semi- Minimal risk of No evidence known to exist by
Programs~ aquatic, aquatic) toxicity the EPA.
EPA Office of Pesticide
Pro
rams
Mammalian wildlife Minimal to
nonexistent risk of
Based on known mammalian
t
di
d 30
f
g toxicity s
u
es an
years o
use.
Soil invertebrates Toxic to some nematode and
Agriculture and Agri-
2
(nematodes
giound Toxic (all strains of ground beetle species; indirect
Food Canada ,
beetles) Bti) adverse effects likely for
predators of such species.
Preliminary DraR Mosquiro Plan 4-2I-03 Final.doc ~
Agenda Item # ~f3 Page # ~~
6.0 Poten[ial Impacts of Bli [o
TABLE 6-1: LITERATURE REVIEW OF TOXIC EFFECTS FROM BACILLUS
~UR/NG/ENSIS SUBSPECIES ISRAELENSIS ON NON-TARGET ORGANISMS
Agency/Source Non-target Effects Comments
Organism
Invertebrate predators Study (Merritt and Wipfli 1994)
Agricu Zture and Agri-Food (flies, dobsonflies, No negative impacts included field and lab testing for
Canada dragonflies,stoneflies, s
__,,,_~:__~ three years.
Agricu Zture and Agri-P'ood Non-target mvertebrates No ill effects Reported by Garcia et al. 1980."
Canada (nearly 100 species)
Non-target aquatic
insects(caddisflies,
Agriculture Canadas mayflies, stoneflies,
damselflies, dragonflies, No demonstrated
water beetles), aquatic effects
invertebrates (Daphnia,
rotifers, crustaceans)
Aquatic vertebrates
(trout, sunfish, frogs,
Agriculture Canadas salamanders), terrestrial No negative effects
vertebrates (mallard,
Total insect density significantly
reduced by 60 percent in second
and third year of normal
treatment. Total dipteran density
significantly reduced by 62
percent and 82 percent in second
and third year of normal
treahnent. Total insect richness
Benthic (number of genera) significantly
macroinvertebrate Delayed toxicity to reduced by 33 percent to 67
b communities (179 many dipteran genera, percent in second and third year
Hershey et al. 1998 genera of aquatic insects mosUy chironomids, of nortnal treatment. Chironomid
and some non-dipteran richness reduced by 43 percent
from 7 orders) in 27 predator genera and 66 percent in second and
wetlands third year of normal treahnent.
Non-dipteran predator genera
richness reduced by 64 percent in
third year of normal treatment.
Results indicate a profound
change in wetland function and
indirect adverse effects are likely
for vertebrate predators of
chironomids (such as waterfowl).
Source Notes:
~ EPA Bacillus tburingiensis subspecies israe[ensrs strain EG2215 Factsheet,
h~rih~w~~ eu•3 ~~ov~ocsticidesibio~csticides/ingrcdi~nts/Pictshects~factsheet OOFi47(i hnnl. Accessed 04/10/03. Webpage
last updated 04/01/03.
` Joung, Kwang-Bo and Jean-Charles CotB. 2000. "A review of the emironmental impacts of [he microbial insecticide Bacillus
thuringiensis." Horticulture Research and Development Centre, Agriculture and Agri•Food Canada,
h[tp:Ures2.ae,r ca's[je•~n/public~~tion/bulletinPoacillus thuringicnsis 4 e.htnt. Accessed 04/03/03. Webpage last updated
03/19/03. Not all primary literature noted here.
~ Merrit[, R.W. and M. Wipfli. 1994. `7mpac[ of Btr on non-target aquatic insec[s and [rou[." Michigan State University,
Preliminary Draft Mnsquito Plan 4-21-03 Final.doc
Agenda Item # ,~_ Page # ~3
6.0 Potentiai Impacts of B(i ro Nontarget Species '
lit(1~_-%H_~v_~p, nisue.msu_ediJmsucJiniplmocicV(il$93003.{itml. Accessed 04/U/03.
° Garcia, R., B. DesRoehers and W. Tozer. 1980. "Studies on the toxicity of Bacillus d~uringiensis var. israe[ensis against
organisms found in association with mosquito larvae.° Proceedings of the Annual Conference of the Califomia Mosquito
and Vector Control Association, pp. 33-36.
' Agriculture Canada. 1982. "Report of new registration: Sacillus thuringiensis serotype H14." Pood Production anA
Inspection Branch. Ottawa, Ontario, Canada.
6 Hershey, A.E., A.R. Lima, GJ. Niemi, and R.R. Regal. I99S. "Effects of Baci[lus tlu+ringiensis israelensis (Bti) and
methoprene on nontarget macroinvertebra[es in Minnesota wetlands." Ecological Applications 8(1): 41-60.
LCso = Lethal concentration to 50 percent of test population.
Agenda Item # SA Page # ~y ~
Preliminary Draft Mosquiro Plan 4-21-03 Final.doc
7.0 POTENTIAL IMPACTS TO WATER QUALITY FROM BT/
_ ~:,~ ~
The potential is minimal for Bti to enter groundwater or other sources of drinking water, and the
bacterium does not proliferate in aquatic habitats (EPA 1998). Bti is suitable for application to irrigation
water and any other water supplies, except for finished drinking water. Labeling requirements must state
that Bti should not be applied directly to treated drinking water reservoirs or drinking water receptacles.
Bti does not readily move from an application site and is unlikely to percolate to groundwater (NPIC
2000). No resh-ictions have been issued for use of this material around bodies of water (EPA 1998).
Agenda Item # -ri H Page # ~~~~
Preliminary DraR Mosqui[o Plan 4-21-03 Final.doc
8.0 EDUCATION
-~~ ~~ G.
8.1 RESEARCH AND EVALUATION
8.1.1. Background
Among the most important roles of public health professionals is assessing the potential impact of a
disease on a population and devising safe and effective methods to reduce the risk of disease
transmission. The ecological relationships among vectors, pathogens, and hosts must be studied to
accwately predict risks associated with mosquito-bome diseases. Existing literature related to the risk
factors associated with WNV has been extensively reviewed in preparing this plan. However, relatively
little is understood. Further research is needed to address questions such as how the virus circulates in
nature, the host preference, host feeding patterns in the vector population, and vector competence.
Furthermore, some of the conirol methods used to manage mosquito populations, especially application of
pesticides for adult mosquitoes, involve potential impact. Alternative control measures lack efficacy or
data on environmental impact to allow their wholesale integration into the IMM plan. The environmental
impact statement and other research endeavors are important tools used to assess potential adverse health
effects associated with exposure to pesticides. Additional research is needed in this area as well as in
assessing improved techniques for control of larval and adult mosquitoes in the City of Boulder.
8.1.2. Activities Planned
• Greystone will continue to work closely with federal, state, and local agencies on research that
will identify the most effective predictors of human illness caused by West Nile Virus in Boulder.
• Greystone will continue to refine its three-level response plan for risk categories of outbreaks of
mosquito-borne disease based on analysis of surveillance data for birds, mosquitoes, mammals,
and humans.
• Greystone will evaluate the most cost-effective methods of surveillance and control.
• Greystone will research and evaluate the potential health and environmental impact from
application of pesticides for conrtol of adult mosquitoes.
8.1.3. Objective
The objective of the plan is to better understand the etiology of mosquito-bome diseases and to assess the
effectiveness of surveillance, prevention, and control methods.
8.1.4. Activities Planned
Greystone will continue to work closely with federal, state, and local agencies on research that
will identify the most effective predictors of human illness caused by WNV in Boulder.
• Greystone will continue to refine its three-level response plan for risk categories of outbreaks of
mosquito-borne disease based on analysis of surveillance data for birds, mosquitoes, mammals,
Preliminary UraR Mosquiro Plan 4-21-03 Final.doc Agenda Item #.5 f~ Page # 7~
8.0
and humans.
• Greystone will evaluate the most cost-effective methods of surveillance and control.
Greystone will research and evaluate the potential health and environmental impact from
application of pesticides for control of adult mosquitoes.
8.2 PUBLIC EDUCATION AND OUTREACH
Greystone will assist the Ciry of Boulder in increasing public awareness of the risk of mosquito-bome
diseases through newspapers, advertising, presentation of materials, and website postings . These media
will be used to convey information on surveillance, prevention, and control. Accurate and timely
information on control will be provided should surveillance data indicate an increased nsk for humans to
contract WNV that would require control of adult mosquitoes using pesticides. Greystone will assist in
coordinating with the Boulder County Aealth Deparhnent to provide the public with the schedule for
application, the type of pesticide to be used, and how to minimize exposure. In addition, the public will
be informed about what to do in the event of pesticide exposure.
To compliment our larval control program and further reduce the risk of Yhe spread of WNV, it is very
important that an extensive public information program exists. In urban settings, a large portion of the
mosquito population usually develops on private property, especially Culex pipiens (our "container"
mosquito).Greystone recommends a policy of zero tolerance to individual property owners and companies
that are needlessly breeding mosquitoes. Enforcement of a policy such as this is beyond our charge at this
time. However, Greystone perceives that this issue will impede the field operations. Once residents
become aware of our operation more responses will come to the website and hotline complaining about
neighbors who are not participating. The field staff has experience dealing with these types of complaints
but we have devoted little time to this perceived problem.
The residents of Boulder can play an integral part in reducing the chance of having to use adulticides, and
the risk of WNV in the City of Boulder. It is important to note that from our experience and the
experience of Dr. Bruce Harrison from the North Carolina Deparhnent of Environment and Natural
Resources, approximately 25% of the residents in Boulder can be expected to take efforts to reduce
mosquitoes in their yards without some type of City enforcement.
Agenda Item # .'~ ~ Page #~
Prcliminary Uraft Mosquito Plan 4-21-03 FinaLdoc
9.0 2003 SUMMARY REPORT
~
A summary report of mosquito surveillance and control will be prepared at the end of the 2003 field
season. The report will follow this general outline:
Introduction
2003 Executive Summary
West Nile Virus Update
Larval Mosquito Control
Larval Surveillance
Mosquito Habitat within City Lands
Waterbodies
Larvicide ApplicaYion
Adult Mosquito Control
Adult Surveillance
Adult Harborage Sites
Adulticide Application
Public Relations and Education
Annoyance Hotline
Summary
Recommendations for 2004 Field Effort
Agenda Item # _5 Page #~
Preliminary DraR Mosquito Ylan 4-2L03 ~inal.doc
10.0 GLOSSARY
~t~a~r ~ ~ ~s
Adulticide: A pesticide used to kil] adult mosquitoes.
I3acillus sphaericus (Bs): a bacterium; type of biological pesticide used to control mosquito larvae in
water.
Bacillus thuringiensis var. israelensis (Bti): a bacterium; type of biological pesticide used to control
mosquito larvae in water.
Encephalitis: inflammation of the brain that can be caused by West Nile Virus.
Gravid traps: mosquito traps designed to attract pregnant female mosquitoes.
Larvae: immature mosquitoes that live in water; stage that hatches from the egg, before adult stage.
Larvicide: a pesticide used to control immature or larval mosquitoes.
Light traps: mosquito traps outfitted with a light to ariract mosquitoes.
Malathion: an organophosphate pesticide used to kill adult mosquitoes.
Meningitis: inflammation of the lining of the brain and spinal cord that can be caused by a virus or
bacteria.
Methoprene: a type of insect growth regulator used to confrol larval mosquitoes.
Mosquito breeding site: a location where mosquitoes lay eggs, often in stagnant water with organic
material.
Mosquito pool: a group of mosquitoes consisting of 1 to 50 individuals of the same species, collected in
an area on the same day and combined for testing to detect the presence of West Nile and related
viruses.
Permethrin: a synthetic pyrethroid pesticide used to control adult mosquitoes.
Pesticide: substance used to kill pests such as insects, mice, and rats.
Resmethrin: a synthetic pyrethroid pesticide used to control adult mosquitoes.
Source reduction: removal or reduction of larval mosquito habitats.
Saint Louis Encephalitis (SLE): a mosquito-bome viral disease that causes inflammation of the brain.
Sumithrin: a synthetic pyrethroid pesticide used to control adulY mosquitoes.
Vector: an organism capable of carrying and transmitting a disease-causing agent from one host to
another.
Viral encephalitis: inflammation of the brain caused by a virus.
Agenda Item # _~ /~ Page #~
Prcliminary DraR Mosqui[o Plan 4-21-03 Final.doc
11.0 REFERENCES
~ ~~~,~~ ~ ~ ~ a ~~~
Adams, K., H. Idreis, K. Rauscher, D. Tovar, S. Simon, and J. Zelnick. 2001. Select Larvicides for
Control of Mosquito Vectors of the West Nile Virus: Efficacy and Health Effects on Non-Target
Organisms. A Research Synthesis. University of Massachusetts, Lowell, Massachusetts. 110
pages.
Boulder County Mosquito Control District (BCMCD). 2002. Annual Report 2002. Prepared by Colorado
Mosquito Control, Inc. Broomfield, Colorado. 23 pages.
Brogeran, S. 2003. Personal communication [Mar telephone conversation with T. Kjensrud, Greystone
Environmental Consultants, Greenwood Village, Colorado. RE: Lab and field identification
techniques]. Entomologist, Minnesota Metropolitan Mosquito Control District. 1 page
Burgis, J. 2003. Personal communication [Apr telephone conversation with T. Kjensrud, Greystone
Environmenta] Consultants, Greenwood Village, Colorado. RE: Thresholds and mosquito
control of disease vectors]. Florida Mosquito Control District. 1 page.
Calhoon, M. 2003. Personal communication [Mar meeting with T. Kjensrud, Greystone Environmental
Consultants, Greenwood Village, Colorado. RE: Mosquito control plans and larval and adult
identification techniques]. City of Fort Collins. 2 pages.
Centers for Disease Control and Prevention (CDC). 2001. Arboviral Encephalitides. Located at:
http://www.cdc.gov/ncidod/dvbid/arbor/index.htm. Accessed April 17, 2003.
CDC. 2001. Epidemic/Epizootic West Nile Virus in the United States: Revised Guidelines for
Surveillance, Prevention, and Control. U.S. Department of Health and Human Services, Fort
Collins, Colorado. 103 pages.
Colorado Department of Agriculture. 2003. Registry of Pesticide Sensitive Persons. Division of Plant
Industry, Lakewood, Colorado. 15 pages,
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Agenda Item # _'~ f~ Page # y S
Preliminary DraR Mosquiro Plan 4-21-03 Final.doc
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State of the Mission as Defined by Mosquito Controllers, Regulators, and Environmental
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15, 2003.
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York, NY.
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Center and University of Wyoming. Greeley, Colorado and Laramie, Wyoming.
Agenda Item # .~ifj Page # ~/G~
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Greystone Environmental Consultants, Greenwood Village, Colorado. RE: Thresholds and
mosquito control of disease vectors). North Carolina Deparhnent of Environment and Natural
Resources, Raleigh, North Carolina. 1 page.
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control efforts in Boulder County]. Colorado Mosquito Control, Inc., Broomfield, Colorado.
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control]. Medical Entomologist, Nebraska Department of Health and Human Services, Lincoln,
Nebraska. 1 page.
Leighton, F.A. 2000. Western Equine Encephalitis [Web Page]. Located at:
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Environmental Consultants, Greenwood Village, Colorado. RE: Mosquito surveillance and
control in the City of Boulder] Boulder County Deparhnent of Health, Boulder, Colorado. 1
page.
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Colorado Mosquito Control, Inc., Broomfield, Colorado. 2 pages.
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at: http://emedicine.com/med/topic3156.htm. Accessed April 15, 2003.
Agenda Item # ~?~ Page # ~~
National Pesticide Telecommunications Network (NPT'N). 2000. Bacillus Thurengiensis Technica] Fact
Sheet [Web page]. Oregon State University, Corvallis, Oregon. Located at: http://nptu.orst.edu.
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at:http://www.nri.org/IPMForum/ipmwd/issue7/7mossies.htm. Accessed on April 18, 2003.
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(Revised 2002). Utah Mosquito Abatement Association, Salt Lake City, Utah.
O'Mal(ey, C. 1995. Seven Ways to a Successful Dipping Career. Wing Beats. 23-24.
O'Neill, C. 2003. Personal communication [Mar meeting with T. Kjensrud, Greystone Environmental
Consultants, Greenwood Village, Colorado. RE: WNV testing, lab techniques]. Weld
CounTy Department of Health, Greeley, Colorado, 1 page.
Pape, J. 2003. Personal communication [Mar and Apr telephone conversations with T. Kjensrud,
Greystone Environmental Consultants, Greenwood Village, Colorado. RE: Thresholds for larval
and adult control of disease vector mosquitoes]. Epidemiologist, Colorado Deparhnent of Public
Health and Environment, Denver, Colorado. 2 pages.
Paul, E.A. and T.J. Sinnott. 2000. Information Bulletin: Fish and Wildlife Related Impacts of Pesticides
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page]. Located at littp://www.nwl~c_usgs,~ov/whats new;fact sheet/fact westnile res.odf.
Accessed April 10, 2003. 2 pages.
Agenda Item #~ Page # `~~
Wagner, R. 2003. Personal communication [Feb telephone conversarion with T. Kjensrud, Greystone
Environmental Consultants, Greenwood Village, Colorado. RE: Information on mosquito
control plans]. Foreman, Minnesota Metropolitan Mosquito Control Disfict, St. Paul,
Minnesota. 2 pages.
Agenda Item # .~/~ Page #~
APPENDICES
~~ ~ ~~ .~ ~ ~~~
Agenda Item # ~~1 Page # ,SG
APPENDIX A
CLASSIFICATION OF BREEDING SITES
~~~ ~~~;~x ~ ~ ;~ ~:
~pe 1 Wetland- Seasonaliv flooded basins and flats
Herbaceous, non-woody, no canary grass, no cattails
Temporary water, uncultivated farmland/woodland pools
Water depth: 6 inches +/- When wet
Type 1.1- Open field (turf grass). Aedes vexans
Type 1.2- Woodland pool in hardwoods, floodplain forests (river bottoms), Ochlerotatus, Aedes vexans
Type 1.3- Woodland pool in hardwood area where only spring Ochlerotatus.
Tvpe 2 Wetland- Inland Fresh Meadow
Canary grass (3 feeY) and sedges, <5% cattails
Temporary water, usually dry soil with high water table, dry in late summer
Water depth: 6-18 inches when wet
Type 2.1- Canary grass meadow (majority c. grass, some sedge)
Type 2.2- Sedge meadow (majority sedge, some c. grass)
Type 2.3- lesser ]rnown veg. associated with temp .water, some c. grass/sedge
Tvpe 3 Wetland- Inland Shallow Fresh Marsh
Succession of cattails, sedges, c. grass at the perimeter
Temporary water, may contain water up to midsummer or may dry up, remains of cattails will aid in id
Water depth: 6-24 inches
Type 3.1- majority c. grass and sedges, some cattails
Type 3.2- majority cattails, some sedge and c. grass
Tvpe 4 Wetland- Inland Deeq Fresh Marsh
Band configuration surrounding or adjacent to permanent open water body. Vegetation bands include c.
grass at perimeter, sedges on shallow water, cattails/broadleaf plants near open water. Duckweed may be
present, partial vegetative mat
Permanent water, year-round water, pockets of open water allows submerged to grow. Less typical
example: irrigation ditch
Water depth: 6 inches-3 feet
Type 4.1- vegetation bands are c. grass and sedges, some cattails, permanent water area is less than area
covered by vegetation
Type 4.2- vegetation bands are cattails, some c. grass and sedges, permanent water area is less than area
covered by vegetation
Type 43- Majority is permanent open water with narrow vegetative bands of a grass, sedges, cattails
Type 4.4- Non-breeding pond. Area has steep banks and vegetation not associated with pest mosquito
development, artificial duck ponds and golf hazards
Agenda Item # _S!~ Page # S/
Tvpe 5 Wetland- Inland Fresh Open Water
Cattails and broadleaf plants surrounding or adjacent to deeper open water with c. grass/sedges in
shallow water at perimeter
Permanent water habitat containing game fish, includes any site directly connected to ]ake, creek, stream,
river. Shallow ponds (+/-10 feet deep) are included
Water depth: +/-10 feet deep fringed by border of emergents
Type 5.1- majority emergent is c. grass and sedges, some cattails, permanent open water area is less than
area covered by vegetation
Type 5.2- majority emergent is cattails/broadleaf, some c. grass/sedges, permanent open water area is
less than area covered by vegetation
Type 5.3- majority is permanent open water with narrow bands of c, grass and sedges
Type 5.4- shallow pond or reservoir (+/- 10 feet deep) that do not contain game fish.
Tvpe 6 Wetland- Shrub Swamps
Alders, wi]lows, dogwood, some herbaceous
Soil is waterlogged during ~'owing season, sites can be isolated or along slow streams/flood plains
Water depth: usually shallow
Type 6.0- majority is covered by canopy of shrub-type vegetation, some a grass, sedges, cattails,
broadleaf.
Tvpe 7 Wetland- Wooded Swamp
Northern conifer swamps that contain tamarack, white cedar, black spruce, balsam fir.
Soil is waterlogged to within few inches of surface during the growing season, sometimes covered with
water
Water depth: varies
Type 7.0- majority of tamarack trees, thick cover of mosses, do not confuse with Type 1.2 or 13
Tvpe 8 Wetland- Boq
Moss, sedges, cotton grass, cranberries, heath shrubs, stunted black spruce, tamarack, sunounding
vegetation is often upland forest.
Soil is waterlogged, covering of moss
Water depth: varies
Type S.1- poorly drained, wet spongy ground usually rich in plant residues. Type 8.2- floating mat often
sunounded by open water
Agenda Item #~ Page # 5 ,~
APPENDIX B
MATERIAL SAFETY DATA SHEET
,~~~~~~~~~n ~~ ~~~~~~.a
Bacillus thuringiensis var. israelensis
Agenda Item # SH Page #, S~
ATTACHMENT B
WETLAND PERMIT APPLICATION
City of Boulder Public Works Department
P.O. Box 791; Boulder, CO 80306 •
(303) 441-3240
APPLICANT INFORMATION
NAME: Ci~y o~ I~ou.~Ae/ DATE: y 21 U3
PHONE NLTMBER: ( 303~ `/YI ~ I g(~ •
ADDRESS: I~. c1. !~s„ x? 4 I
PROJECT INFORMATION
STTE LOCATION: p~I rcyu.la~e,~ we} ~Ahd~ ok Ci~ o".)k~d.. (at,d5 .
PROPERTY OWNER:
WETLAND DESIGNA
WETLAND FUNCTIO.
WETLAND AREA AFFECTED (acres) I ~ ~JO
BiIFFER AREA AFFECTED (acres) ~~q
MITIGATION AREA (acres) N~µ
APPLICATION REQUIREMENTS
According to Sections 9-4-2, 9-12-6, and 9-12-8 of the Boulder Revised Code, 1981 (B.R.C.), an
application for a wetland permit must include the following information. Please indicate where
the informadon is located in the submittal (page/pazagraph):
Staff Applicant
^ ~/ I Legal description of the property;
0 Notification mailing labels;
^ Vicinity map;
0 A copy of the regulatory wetland aerial map indicating the site location;
^ I a I Description of the proposed activity and how review criteria aze met;
^ ~ I,~ Exact locations and specifications for all proposed regulated activities;
^ 2 Discussion o£ direct and indirect impacts of proposed regulated activities;
^ 3 y ~~. Alternatives analysis including:
^ Description of why avoidance and less damaging alternatives have
been rejected;
^ Demonstration that all adverse impacts on a wetland have been
avoided, or that avoidance is not feasible
D Demonstration that any adverse impact on a wetland h•as been
minimized
~ Demonstration that the activity will result in minimal impact to any
Agenda Item # 5~ Page #. S~/
Form Date: Ol/07/98
wet(and function
APPLICATION REQUIREMENTS (continued)
^ ~` Z Critical species surveys and cleazances; _
^ z~ ~ Demonstration of public need including an analysis of the following:
^ Extent of the public need for the proposed activity;
p Functional values of the wetland;
^ Extent and permanence of adverse effects;
^ Cumulative adverse effects of past acfivities on the wetIand;
^ tJniqueness or scazcity of the wetland.
^ /l~ ~ A Site Pian which shows:
^ Ttegulatory wetland and buffer azea boundaries;
^ Property boundary;
^ Existing and proposed facilities and structures;
^ Direct impacts and encroachments into regulatory areas.
^ ~i~ Information on any fiIl material to be used:
^ Source and type
^ Method of transport and disposal
^ Certification that placement of the fill material will not violate
~ applicable state and federal statues and regulations
bl
Mi
i
i
Pl
if
ii
^ _
` app
t
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on
ca
e.
an,
APPLICATION MATERIALS
List of Plans and Iieports included in this application submittal:
^ County Assessors azea map
0/ Vicinity map
Q" City regulatory wetland aezial map
^ Site Plan
~ Watlands Application Report
0 Mitigation Pian
^ Federa1404 Permit Applications
~ Species surveys and cleazances
Other:
0
d
0
^
Agenda Item # %'/~ page #~_
Form Datc: 01/07/98
Attachment K: Wetland Permit Criteria for City of Boulder West Nile
Virus Control Plan '
1.0 Description of the Proposed Activity
The City of Boulder is proposin~ to implement mosquito control measures to reduce the
threat of West Nile Virus (a mosquito-borne virus) to the city's residents. Two Colorado
species of mosquito are known to transmit West Nile Virus to humans; Ciilec Pipieits and
Culez tarsnlis. Starting in May, wet)ands regula[ed by the Ci[y of Boulder will be
surveyed to determine if either of these two species occurs. Areas include all of the city-
owned lands within the city limits (approximately 311 acres) and a[ least a portion of the
approximately 1400 acres of the city owned Open Space lands outside of the city limits.
Larval control measures will consist of treatment of wetlands with a bacteria that attacks
mosquito larva (BaciRus tlti~rirtgiensis israelensis or Bti). The wetland permit application
addresses any wetland where larva of either of the two species of mosquitoes is found.
Control of the larva will limit the possible future need for nonbiolo~ical control of adult
tar;et rnosquitoes, such as spraying with adulticide.
Impacts to the wetlands include the potential for killin~ not only the tar~eted mosquito
larvae, but other invertebrates, primarily of the order Diptera (true flies). Althoueh the
toxic effects of the applied bacteria generally dissipates within a few days, the annual ]ife
cycle of some of the affected species of flies will result in their not repopulatin~ the
wetlands until the next year.
A detailed WNV control plan is currently being prepared and will be available on the
city's website in mid-may.
1.1 Purpose and Objectives
The purpose of this WNV controt effort is to reduce the risk of human WNV infection
while providing the most minimal affect to the environment possible. Because the larval
control efforts consist of treatment of wetlands with a bacteria that has some impact to
aquatic biodiversity, these activities within the city-re~ulated wetlands will need to be
authorized by a wetland permit.
The objectives that witl be used to accomplish this purpose are:
Objective 1: Map (in GIS format) potential mosquiro breeding habitats within city-owned
lands. This will allow accurate tracking of data for efficient and effective control as weli
as provide reliable information for our 2004 recommendations.
Objective 2: Identify which habitats support the two tar~et species. This will allow
treatment of only the wedands contaiinin~ the two t~rvet species and will reduce the
number of wetland habitats were treatment is necessary. Many other controi pro~rams
treat all habitats where significant mosquito populations are found, regardless of what
Agenda Item # ~ f} Page # .~
species they are. This will substantially reduce the environmental impacts to the City's
wetlan¢s.
Objective 3: Apply '~he larvicide (Bti) to any wedands where either of the two tareet
species are found. This ]evel of control effort conducted during the larva] sta~e is the
most effective and environmentally friendly way to eliminate the target mosquito species
and, [herefore, reducing the potential for ~VNV-canying adult mosquitoes. This will
(ower the likelihood of the possible need for adulticide sprayin; if WNV turns epidemic.
Objective 4: Collect data on the locations of actual WNV occunences within the City of
Boulder owned lands (for mosquitoes, birds, and mammals). This will include; a)
conductin~ direct WNV testin~ within the adult mosquito populations of the two taraet
species; and, b) coordination with ]ocal and state a~encies on the results of bird and
mammal WNV findings within the city.
Objective 5: Develop a public education and awareness prob am inctuding the creation of
a West Nile Virus Control Plan (Plan) to inform the public why there is a need for the
control efforts and to describe what the control efforts will antail. Other efforts include a
inFormation pamphlet that will ue distributed with the utility bill.
1.2 Intended Use
The intended use of the project is for the protection of public health and safety
13 Description of Related Facilities
No facilities are proposed as part of this project.
1.4 Start Date of Activity
Treatment with Bti will start on May 14, or when permit is granted, whichever comes
first. The duration will be tfirough September 2003
1.5 Extent of Public Need
The pubiic need for this project is to protect the health and safety of the public and
animlls.
1~.6 Wetland Functional Values that May be Affected
The functiona( values that may be affected are a reduction in the abundance and diversitY
of aquatic life wi[hin any of the wedands that are treated
1.7 The Extent and Permanence of the Adverse Effects on the Wetlands
Agenda Item # ,~ Page #. 5 7
Although the toxic effects of the applied bacteria generally dissipates within a few days,
the annual life cycle of some of the affected species of flies will result in their noc
repopulating the wetlands until the next year. -
1.8 Cumulative Adverse Effects of Past Activities on the Wetlands
Because the activity proposed is not typical of the activities that may have occurred to
some of the wetlands to be treated, there will be no cumulative adverse effects from this
project.
1.9 Uniqueness and Scarcity of the Wetland that May be Affected
Because all of the re~ulated wedands owned by the city of Boulder have the poten[ial to
be treated, the uniqueness and scarcity will be varied to the extent of uniqueness and
scarcity that exists within these wetlands.
2.0 Altematives Analysis
2.1 Alternatives Analysis from a Wetlands Perspective Only
Seven alternatives were selected for analysis ranking. Each of these alternatives was
chosen because they are al] viable methods for mosquito control and have all been used
in other mosquito control programs. The alternatives are: application of Bti, application
of Bs, application of Methoprene, stocking of predatory fish, application of oil, mosquito
breeding habitat manipulation, and the no action. These methods have standard protocols
required to achieve the necessary control. Therefore, there aze no ways to avoid wetland
impacts through alteration of each alternative. Accordingly, we have discussed the impact
of each alternative and provided the ranking along with the discussion. The ranking of the
alternatives begin with 1 being the best wetland alternative and 7 being the least
environmentally protective.
Alternative Ranked 1- No Action
The no action altemative would be the best wetland alternative because no disturbance
would occur in regulated wetlands within the City of Boulder excep[ for larval sampling
and collections.
Altemative Ranked 2- Bti treatment
Bti is a microbial insecticide that will be used to control mosquito larvae. Use of Bti in
wedands poses two identified maximum potential impacts. First, it may kill 98 percent of
mosquito larvae within a treatment area (MMCD 2002). This high percentage poses a
potential to disrupt the food chain by removin~ a source of food that predators could use.
Second, it has the potential to kill non-target dipteran species (EPA 1998 and 2002; ETN
2U03; NPTN 2000), which also could affect the food chain. However, because it does not
kill many of the nontarget aquatic species in a wetland, the entire food chain would not
be broken. The residual for /3ri in water is about 24 hours, nnd it breaks down ripidly as a
Agenda Item #~ Page # . `~ S~
result of exposure to ultraviolet light (EPA 1948). As a result,•adult mosquitoes and other
dipterans could lay eg~s in the treated ~~~ater 24 hours after a treatment, and larvae could
develop to provide another source of food to predators. -
Tt is not ]ikely to substantially affect bird species that feed in wetlands because we
estimate that as much as 80 percent of the wetlands will not be treated and would
therefore supply adequate food resources. Bti is non-toxic to birds (ETN 2003; NPTN
Z000)
AI[erna[ive Ranked 3- B. Sphaerici~s Treatment
B. sphaericeis is similar to Bti in that it is a bacterium, but the differences are significant.
Use of B. spliaerici~s in wedands poses three identified maximum potential impacts. First,
it kills mosquito larvae within a treatment area (MMCD 2002), Thus, B. sphnericus has a
potential to disrupt the food chain by removin~ a source of food that predators could use.
Second, it has the potential to kill non-target Diptera species, which could also affect the
food chnin. Third, the residual for B. sphaericus in water is 2 to 4 weeks (Charlas and
Nielsen-LeRoux 2000; McGinnis 2000) Therefore, aggs that are laid within 4 weeks of a
treatment have the potential to be affected by B. sphaerica~s, causin~ a break in the food
chain that lasts lon=er than with Bti.
It is not likely to substantiatly affect bird species that feed in wetIands because many
wetlands would remain in the City of Boulder that would not be treated and that wou]d
supply adequate food resources.
Alternative Ranked 4- Stocking of Predatory Fish
The biolo~ical control of mosquitoes often includes top-water feeding minnows such as
Gnmbusia affinis (mosquito fish) or plains killifish (Fundulus zebrinus). Similar to Bti
and Bs, stockin~ of predatory fish is eonsidered biological control. However, fish are tess
species selective than are the two bacteria species. Fish introduced to a wetland will eat
mosquito larvae as well as all other palatable aquatic ]ife in the wedand.
Alternative Ranked 5- Application of Methoprene
Methoprene is different from Bti and B. sphaericus because it is a hormone, and not a
bacterium, and it does not immediately kill the mosquito larvae (EPA 2002). The
hormone does not allow the larvae to develop into an adult, and the mosquito dies at the
pupa sta~e (EPA 2002). Use of inethoprene in wet(ands poses two identified maximum
potential impacts. First, it affects more non-target species than do Bti and 8. spliaericus,
includin~ fish and aquatic invertebrates. Second, the residual for methoprene in water
varies dependin~ on the form of the product: 21 days (sand), 30 days (pellet), or 150 days
(briquette) (MMCD 2002). This lon~ residcnce time poses a significant risl: to the
biological function of wetlands.
Agenda Item # 5 f~ Page #~
It is not likely to affect bird species that feed in wetlands because many wetlands would
remain in the City of Boulder that would not be treated and that would supply adequate
food resources. _
Alternative Ranked 6- Application of Oil
The application of oils to water is not species-specific (EPA 2002). The oil will kill any
aquatic species [hat lives near the surface or that depends on a bveathin~ tube to survive.
This altemative could severely affect the biodiversity and abundance of aquatic life
within a wetland.
Altemative ltanked 7- Mosquito Breeding Habitat Manipulation
The actions involved in habitat manipulation often dewater the wetland. Dewaterin~ can
permanently change the function of the wetland and can severely affect the ecological
integrity of the wetland ecosystem. Enou~h manipulation to eliminate mosquitoes would
eliminate many of the wetland species; both animal and plant.
2.2 Comprehensive Altematives Analysis
The same seven alternatives were selected for analysis ranking. These methods have
standard protocols required to achieve the necessary control. Therefore, there are no ways
to avoid wedand impacts through alteration of each alternative. Accordingly, we have
discussed the impact of each alternative and provided the ranking along with the
discussion. The ranking of the alternatives begin with 1 being the best over-all alternative
and 7 being the least favorable over-all altemative.
Alternative Ranked I- Application of Bti (Best Overall Alternative)
Bti is a microbial insecticide that will be used to control mosquito ]arvae. It is desirable
for several reasons. First, its residual lasts only 24 hours in water (EPA 1998 and 2002;
ETN 2003; NPTN 2000). Second, it does not affect many non-tar~et species, such as fish
(EPA 1998 and 2002; ETN 2003; NPTN 2000). Third, the bacterium kills the mosquito
larvae, and field technicians can see results the same day the Bti is applied. A ne~ative.
effect is that part of the food chain is temporarily removed by kiltino the larvae,
potentially affectin~ predators by removing a source of food.
This altemative has been selected as the best overall altemative because it serves the
oreatest public need. The threat that WNV will infect residents of Boulder outwei~hs the
relatively low impacts this bacterium may huve on the wedands in which it is used.
Lurvul treatments must occur in order to contuin and minimize the threat of WNV
ini'ection in humans and this larvicide will have the least effects on wetlands.
Adverse impacts to wetlands will be minimized by upplyin~ Bri at recommended
concentrations, and all treatment ureas will be posted with signs before Bti is appiied.
Agenda Item # .~ ~ Page # l~ ~
A list of the Boulder Valley plant and animal species of local concern was reviewed
(Blum 2003), and it was determined that there will be no adverse effects to any of the
species or their habitats. Bti will be applied at the rates recommended on the product label
for mosquito ]arva control. It has been shown that, when applied at the recommended
rates for mosquito lar~~a control, Bti only has adverse effects primarily on mosquitoes and
other dipterans. This project will not disturb or modiFy habi[ats for any of the listed
species. ,
Direct and Indirect Impacts of Bti
Direct impacts to the wetlands from treatment with Bacillus thuringiensis israelensis
(Bti) include the potential for killing not only the targe[ mosquito species (C. tarsalis and
C. pipiens), but other insect species in the order Diptera and'potentially even outside a
the dipterans. Many nontarget aquatic invertebrate species will not be affected by
applications of Bti. Indirect impacts include the potentia] for an interruption in the food
chain for species that typically feed on the mosquito larvae. Although the toxic effect~ ~~
Bti seneral; 3issipate within a few days, the annual life cyde of some of the affectec
species of flies will resul[ in their not repopulatin~ the wet]ands until the next year.
Not all wetlands will be trea[ed, however, because surveillance will show that not all
wetlands will support habitat for or populations of the two target species, ]imiting the
effects on the food chain. These untreated wetlands will continue to support mosquitees
and other dipterans to maintain continuity in the food chain and be available to facilitate
repopulation of the treated wetlands. Additionally, wetlands that support the target
species may not be fully treated because areas of habitat that support these populations
will be spot-treated. In this case, only a portion of the wetland will be affected, further
maintainin~ continuity of the food chain even in some treated wetlands. Table 1 is a
summary of potential direct and indirect effects resulting from Bri.
Agenda Item # _~ Page # ~ /
Table 1: Literature Review of Toxic Effects from Bacillus thuririgiensis subspecies
israelensis on Non-tar~et Organisms •
Agency/Source Non-target Effects Comments
Agriculture and Agri- invertebrate predators no negative impacts Study (Mertitt and Wipfli
Food Canada~ (flies,dobsonflies, 1994)included field andlab
draaonflies, stoneflies, testing for three ye~rs.'
Agriculture and Agri- nomtarget no ill effects Reported by Garcia e[ al.
Food Canada' imertebrates (nearly 1980.°
100 species)
Agriculwre Canada' nomtar~et aquatic no aemonstratea
insects (caddisflies, effects
mayflies, stoneflies.
damselflies,
dra~onflies, water
beedes),aquatic
invertebrates
(Daphnia, rotifers,
crustaceans)
Agriculture Canada' aquatic vertebrates no negative effects
(trout, sunfish, frogs,
salamanders),
tertestrial vertebrates
et al. 1998° benthic
macroinvertebrate
communities (179
genera of aquatic
insects from 7 orders)
in 27 wetlands
Sourcc Noies:
delayed roxicity ro Cotal msect densiry
many dipteran significantly reduced by 60
genera, mosdy % in second and third year of
chironomids, and normal treatment. Total
some non-dipteran dipteran density significantly
predator genera reduced by 629o and 82~7o in
second and third year,
respectively, of normal
treatmen[. Total insect
richness (i.e., number of
genera) significan[ly reduced
by 33%-67% in second and
third year of normal
treatment. Chironomid
richness reduced by 43~7o and
66~/e in second and third
year, respectively, of normal
treatment. Non-dipteran
predamr genera richness
reduced by 64%n in third year
of normal [rwtment. Results
indicate a profound chanpe in
wetland function and indirec[
adverse effects nre likely for
~ ertebrate predators of
~hironomids (e.g.,
Agenda Item # _~ Page # G~~
~ EPA BacilG~s thuringiensis subspecies israelensis strain EG2? IS Factsheet, •
httn~/l~~~ww ena ~ov/~cticideelhio~siicidedinercdients/factshecic/I~iciaheet 006d76 html. Accessed O~i/10/03.
Webpaee I~st updated 04/01/03.
= Joune. Kwang-Bo and Jean-Chades Cot6. 2000. "A review of the environmental impacts of Ihe microbial .
insecticidc Bacilltts tlutringie~~sis." Hotticulmre Research and Development Centre, Agriculmre and Agri-Food
Canada, h~t •Ures' atR c;ilstiean/oublicaiion/hulletin/bacillus ~hunm~ien+ie d ehim. Accessed 04/03l03. Webpage
last updated 03/19/03. Not all pnmary literamre noted here.
' Mertitt, R.W. and M. Wipfli. 1994. "Impact of Bti on non-target aquatic insects and trout" Michigan State
University, h~~//www mzue msu.~du/msue/im~lmodet/61893001.himl. Accessed04/17l03.
' Garcia, R., B. DesRochers and W. Tozec 1980. "Smdies on the toxiciry of BaciUus du~ringiensis var. israe/ensis
aeainsl organisms found in association with mosquito larvae." Proceedings of the Annual Conference of the CaliFomia
Mosquito and Vector Con[rol Association, pp. 33-36. ~
5 Agriculmre Canada. 198~. "Report of new registration: Bacillus thuringiensis serotype H14." Food Production and ~
Inspection Branch. Ottawa. Ontario. Canada.
b Hershey. A.E.. A.R. Lim~. GJ. Niemi, and R.R. Regal. 1998. "EfFects of Bacillus dturingiensis israelensis (8ri)
and methoprene on nonearget macroinvertebraces in Minnesota wedands" Ecological Applications 8(1): SI-60.
The bacterium Bti has been studied and in use as a mosquito larvicide for about 20 years.
Hundreds of peer-reviewed scientific journal artides and ~ovemment agency documents
have been published about the po[ential for ecological effects from Bti. It appears; based
on a review of several summary publications from reputable federal government
aeencies, that Bti is nonroxic to nearly all types of non-target organisms (i.e., tazget
organisms for Bti are mosquitoes and black flies), including other insects, with two
exceptions. Bti is toxic to soil microorganisms (e.g., nematodes) and may be toxic to
Dnpluiia (a ~enus of freshwater invertebrate crustacean), accordin~ to the US EPA and
A~riculture and Agri-Food Canada. This information is summarized in Table 6-1.
However, most of the studies cited by the govemment summary documents were
conducted in the laboratory for a short duration and only considerin~ the effects to the
study organisms themselves. Two studies published in 1998 provide contrastin~
evidence of more wide-ran~ing target effects to nontarget species. One of these studies
(FCCMC 1948) determined that, while Bti is highly effective at killing [he targeted
mosquito larvae (C. tarsalis and C. pipiens), it is also ]ethal to many other insect species
in several taxonomic orders besides Diptera (flies). Some ]arval mortality of insect
species that aze normally associated wiih mosquito larvae in aquatic habitats was
observed in the Families Chironomidae (mid~es), Ceratopo~onidae (biting midges), and
Dixidae (dixid mid~es). However, the concentration of Bti required to cause this effect
was 10 to I,000 times higher than normal application rates for mosquito control. In
another study (Hershey et al. 1998, see Table 6.1) of Bti applied for three years at normal
rates to 27 wedands, adverse impacts to insect and non-insect orders were delayed until
the second year of application. In the second and third years of application, significant
reductions in insect abundance and insect species richness were observed. Overall insect
community composition was radically altered and the authors speculated that many
species were adversely impacted indirectly via ch~n~es to the ecosystem structure. The
au[hors also estimated that wetland function had been disrup[ed and de~raded, likely
causin~ indirect effects to wetland vertebrates that could not be measin'ed in the three-
year timespan.
Altemative Ranked 2- Application of B. sphaericus
Agenda Item # ~ A Page # (~ .3
B. sphaericus was evaluated as an altemative for control of WNV but was eliminated. It
is similar to Bti in that it is a bacterium, but the differences are significant. It is desirable
becau~e, like Bti, it kills the mosquito larvae, and field technicians can see results the
same day the bacterium is applied. Certain factors make this product undesirable for use
in the Ciry of Boulder, however. First, the residual remains in water for 2 to 4 weeks
(Charles and Nielsen-LeRoux 2000). In addition, it has the potential to kill non-tareet
species within the order Diptera (Charles and Nielsen-LeRoux 2000). Furthermore,
mosquitoes have been shown to develop resistance, which reduces its effectiveness
(Charles and Nielsen-LeRoux 2000). Finally, part of the food chain is temporarily
removed, potentially affecting predators by removing a source of food.
AI[emative Ranked 3- Stockin~ of Predatory Fish
The biological control of mosquitoes often includes top-water feeding minnows such as
Gambaisia affinis (mosquito fish) or plains killifish (Fundulus ze6rinus). Similar to Bti
and Bs, stocking of predatory fish is considered biological control. However, fish aze less
species selective than are the two bacteria species. Fish introduced to a wedand will eat
mosquito larvae as well as all other palatable aquatic life in the wetland.
Alternative Ranked 4- Application of Methoprene
Methoprene was also evaluated as an altemative for WNV control but was eliminated. It
is different from Bti and B. sphnericus because it is a hormone, and not a bacterium, and
it does not immediately kill the mosquito larvae (EPA 2002). The hormone does not
allow the larvae to develop into an adult, and the mosquito dies at the pupa stage. It is
desirable because it does not kill the larvae so the food chain remains intact and there are
no effects on predators. In contrast, it is undesirable because the mosquito larvae are not
killed, and field technicians cannot see results in the field. The inability of field
technicians to immediately see results could be undesirable. If a larvae population is
treated that is positive for WNV, and treatment is not effective, adults wil] emerge and
can spread WNV. With Bti or B. sphaericus, field technicians can verify that the
treatment was effective within 24 hours, and can reapply the larvicide if it was not
effective. Additionally, its residual is 21 days (sand), 30 days (pellet), or 150 days (block)
in water. It also affects more non-target species than does Bti, including fish and aquatic
invertebrates. Finally, ultraviolet rays from the sun also tend to break down methoprene,
reducing its effectiveness (MSDS 2000). Because Colorado is sunny, it is not the best
prod~ct to use here.
Alternative Ranked 5- Application of Oil
The application of oils to water is no[ species-specific (EPA 2002). The oil will kill any
aquatic species th~t lives near the surface or that depends on a breathin~ tube to survive.
This alternative could severely affect the biodiversity and abundancc of aquatic life
within a wetland.
Alternative Rankecl 6- Mosquito Breeding Habitat Manipulation •
Agenda Item #~_ Page #~
The actions involved in habitat manipulation often dewater the wetland. Dewatering can
pertttanently change the function of the wetland and can severely affect the ecological _
integrity of the wetland ecosystem. Enou~h manipulation to eliminate mosquitoes would
eliminate many of the wetland species; both animal and plant.
Altemative Ranked 7- No Action
The no action alternative was not chosen as the best overall alternative because it does
not serve the public need to control the epidemic of WNV in highly populated areas. The
threat that WNV will infect residents of Boulder outweighs the minimal impacts Bti may
have on the wetlands where it is used. Larval treatments must.occur to contain and
minimize the threat of WNV infection in humans, and this ]arvicide will have the least
effects on we[lands. Furthermore, selection of the no action alternative could actually be
the most harmful to the env; ~~ment because the lack of control of the WNV-carryin~
mosquito species has the possieility of resulting in a substantial outbreak of WNV in
humans, which would require spraying of adult mosquito habitats with pesticides.
2.2 Justification for Choosin~ an Option Other than the Best Wetland Alternative
Justification for choosing B[i instead of the no action altemative is primarily due to the
risks that WNV is to the health and safety of the public. Refer to the preceding sections
for detailed justifications.
3.0 Critical Species Surveys and Cleazances
A list of the Boulder Valley plant and animal species of local concem was reviewed
(Blum 2003)(Appendix A), and it was detemvned that there will be no adverse effects to
any of the species or their habitats. Bri will be applied at the rates recommended on the
product label for mosquito larva control. It has been shown that, when applied at the
recommended rates for mosquito larva control, Bti has adverse effects primarily on
mosquitoes and other dipterans. This project will not disturb or modify habitats for any of
the listed species.
The proposed project is unique in terms of the permittin~ process because no dred;e and
fil] is involved, and it will not contribute significantly to adverse effects to wedands in
the City of Boulder.
4.0 Site Plan
The locations of the proposed activities are on any of the Ciry-regulated wedands as
identified by the City of Boulder's G1S covera~es for resulated wedands. Please refer to
these City of Boulder and Boulder Open Space wetland maps within your GIS
depaiKment. Because it includes all of the regu-ated wedands, a legal description of the
property, vicinity map, site plan, and copy of the re~ulatory wedand aerial map are not
applicabie to this permit. Furthermore, there ~re no existing nnd proposed f~cilities and
Agenda Item # _~ Page # ~.5
structures, direct impacts and encroachments into regulatory areas, or fill materials for
this project. ~
5.0 Mitigation Plan
We are proposing no mitigation for these activities because the benefits to the public
health and safety outwei~h the relatively low impact on the wetland functions.
Agenda Item # ~S/3 Page # ~v~
6.0 REFERENCES
Blum, V. 2003. Personal communication [April 17 email to Patrick Golden, Greystz :~e, _
Greenwood Village, Colorado. RE: Boulder Valley Comprehensive Plan, Plant
and Animal Species of Local Concern in the Boulder Valley]. Civil Eneineer,
Floodplain and Wetland Permittin~, Planning and Development Services, City of
Boulder, Boulder, Colorado. 4 pages. ;
Charles, J.F. and C. Nielsen-LeRoux. 2000. Mosquitocidal Bacterial Toxins: Diversity,
Mode of Action, and Resistance Phenomena. Momoria] Institute Oswaldo Cruz,
Rio de Janeiro. 95, Supplement 1: 201-206.
Environmental Protection Agency (EPA). 2002. Larvicides for Mosquito Control [Web
pa~e]. EPA Region 10. Located at
http•//ep~ ~ov/pesticides/factsheets/larvicides4mosauitos.htm. Accessed: March 3,
2003.
EPA. 1995. Reregistration Eligibility Decision for Bacillus Thuringiensis. EPA,
W ashington D.C. 156 pages.
Extension Toxicolo~y Network (ETN). 2003. Bacillus Thuringiensis [Web pa~e]. Comell
University, Ithaca, NY. Located at:
h~'/lomep cce comell edulprofiles/extoned24d-captan/bt-ext html. Accessed:
February 21, 2003.
McGinnis, M.W. 2000. Mosquito control, The Environment and You. Colorado Mosquito
Control, Inc. 1993 (4i6 revision, January 2000).
Metropolitan Mosquito Control District (MMCD). 2002. 2002 Field Operations Manual.
Revised March 2002. Metropolitan Counties Government Center, St. Paul,
Minnesota. 237 pages.
Material Safety Data Sheet (MSDS). 2000. MSDS for Zoecon Altosid Pellets [Web
page]. St. Lucie Mosquito Control District, Florida. Located at
http•/hvww stlucieco.eov/msq/fos/chemicals.htm. Accessed April 18, 2003.
National Pesticide Telecommunications Nehvork (NPTN). 2000. Bncillue• 7'In~ringiensis
Technical Fac[ Sheet (Web paae]. Oregon Sta[e University, Corvallis, OR.
Located at htto://nptu.orst.edu. Accessed: Aprii 17, 2003.
Agenda Item # .~ f} Page #~
pppendix A~ Boulder Valley Comprehensive Pian - Plant,and Animal Species of Local
Concem in the Boulder Valley ~
Agenda Item #~ Page # G> ~