RES 2007-13 NOXIOUS WEEDSRESOLUTION NO. 2007-13
A RESOLUTION OF THE CITY OF BAINBRIDGE
ISLAND, WASHINGTON, APPROVING EMERGENCY
PROCEDURES FOR THE APPLICATION OF
PESTICIDES FOR INVASIVE KNOTWEED
ERADICATION.
WHEREAS, Policy CF1.1 of the Comprehensive Plan of the City of Bainbridge
Island states that the City "shall encourage protection, restoration and maintenance of
existing vegetation that has environmental, wildlife habitat and aesthetic qualities,
including tree groves, significant tree stands, forested hillsides, and vegetation associated
with wetlands, stream corridors and riparian areas"; and
WHEREAS, Policy CF1.5 of the Comprehensive Plan of the City of Bainbridge
Island encourages the City to control and prevent establishment of invasive species that
are destructive to forest health; and
WHEREAS, several invasive knotweed species have become prevalent along
public rights-of-way, in public parks, and on private property, and are threatening
roadway safety and the environment; and
WHEREAS, knotweed species are Class B weeds on the Washington State and
Kitsap County Noxious Weed Lists and are required by law to be controlled; and
WHEREAS, BIMC Chapter 16.30 contains regulations regarding pesticide use
on public lands; and
WHEREAS, mechanical control methods have proven ineffective and
impractical for controlling and eliminating knotweed species on public lands; and
WHEREAS, best management practices and best available science for the control
of knotweed species currently includes relatively low toxicity methods that can only be
authorized on public lands under the emergency procedures clause contained in BIMC
16.30.040; and
WHEREAS, attached as Exhibit A and incorporated herein by this reference is a
is a copy of a written rationale for the use of emergency procedures to control knotweed
species; and
WHEREAS, pursuant to BIMC 16.30.040, the director of public works has
determined that the threat to public safety and the environment caused by knotweed
species is an emergency situation requiring the use of pesticides not on the City's least
toxic pesticide list; now, therefore,
THE CITY COUNCIL OF BAINBRIDGE ISLAND, WASHINGTON,
DOES RESOLVE AS FOLLOWS:
Section 1. Emergency Procedures for Knotweed Eradication.
Pursuant to BIMC 16.30.040, the emergency procedures described in Exhibit A are
authorized for the control and eradication of knotweed on public lands. The Director of
Public Works shall have the authority to approve the use of other products and associated
best management practices consistent with this authorization. The Director of Public
Works shall submit a report consistent with BIMC 16.30.080 at least annually and any
time a new product is authorized for use.
Section 2. Duration, Review, and Renewal.
Pursuant to BIMC 16.30.040, this authorization is approved for a limited time of five (5)
years, after which time the Director of Public Works shall prepare a report to the City
Council regarding the effectiveness and results of the emergency procedures as well as
the continued need and appropriateness of the emergency procedures. Upon the findings
and recommendation of the Director of Public Works, the City Council may renew this
authorization for a limited time.
PASSED by the City Council this 25th day of April 2007.
APPROVED by the Mayor this 26th day of April 2007.
Darlene Kordonowy, Mayo
ATTEST/AUTHENTICATE
Rosalind D. Lassoff, CMC
City Clerk
FILED WITH THE CITY CLERK: April 10, 2007
PASSED BY THE CITY COUNCIL: April 25, 2007
RESOLUTION NUMBER: 2007-13
RESOLUTION 2007-13: EXHIBIT A
Emergency Procedure Report
Prepared, reviewed and edited by the Bainbridge Island Knotweed Working Group: Dale Spoor,
Maria Mason, Deborah Rudnick, Dana Coggon, Jane Wentworth, Bobbie Morgan, Brian Stahl,
Peter Namtvedt Best
A. Nature of the problem, reason for the declared emergency, need to use pesticides
The nature of the problem
Knotweed has been identified by the Kitsap County Noxious Weed Control Board as a class
B weed that is required to be controlled in Kitsap County on both public and private lands.
Knotweed was first identified as a problem on BI in an article in "Scotch Broom" in 2001.
Knotweed is distributed fairly widely across the Island and is becoming particularly
widespread in parts of the northern end of the Island (See attached map: Knotweed
Distribution).
The reason for the declared emergency
Knotweed has been rapidly spreading on Bainbridge Island. Left uncontrolled, knotweed
quickly outcompetes native plants and can cause serious ecological impacts including loss of
stream and wetland habitat and increased erosion. On Bainbridge, knotweed is growing
thickly in many roadside areas and reducing visibility, and is therefore also a serious threat to
roadway safety. Immediate action needs to be taken. Under the provisions of BIMC 16.30
pesticides not on the Least Toxic Products List cannot be used for control of vegetation on
public lands. Section 16.30.040 Emergency Procedures needs to be invoked so that effective
pesticides can be used to control knotweed.
The need to use pesticides not on the Least Toxic Products List
Multiple research studies and county and other programs have shown that knotweed patches
larger than a few tens of square feet, such as many of those found on Bainbridge Island,
cannot be successfully controlled by mechanical means. Other methods which have been
tried on Bainbridge Island, such as manual cutting and bagging of the plants, are not effective
because they cannot keep pace with the rate of spread and regrowth of this plant. Targeted
use of herbicides in this situation is the only approach that has been shown to be practical and
successful in the control and eradication of knotweed.
B. The Knotweed Control Work Group has consulted with the following groups and entities:
• Bainbridge Island Weed Warriors
• King County Noxious Weed Control Program (Sasha Shaw)
• Kitsap County Conservation District (Brian Stahl)
• Kitsap County Noxious Weed Control Board (Dana Coggon)
• The Washington State Department of Agriculture Knotweed Control Program
(Marshall Udo, Knotweed Control Coordinator)
• The Washington Toxics Coalition
• The Nature Conservancy (April Johnson)
• Seattle Parks and Recreation IPM Coordinator (Barbara DeCaro)
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RESOLUTION 2007-13: EXHIBIT A
Debbie Rudnick, Ph.D. Ecologist (10,000 Years Institute, Bainbridge Island
Watershed Council)
Jane Wentworth, M.S. Chair, Kitsap County Noxious Weed Control Board
And in addition several website have been reviewed, including:
• The Washington State Department of Ecology:
http://www. ecy.wa. gov/programs/wq/pesticides/seis/risk_assess.html
• The Nature Conservancy Wildlands Invasive Species Website: Knotweed Page:
tncweeds.ucdavis.edu/esadocs/polybohe.html
According to the information received from the above sources, the least toxic and least
persistent pesticide(s) currently being used to effectively address the problem are: glyphosate
either injected or used as a foliar spray, or imazapyr used as a foliar spray. Other pesticides
may be used in the future based on continual assessment, current scientific data, and best
management practices. The resource management community is in consensus that these are
the best techniques currently available, and combinations of these approaches are being used
specifically by the following:
• Kitsap County Noxious Weed Control Board
• King County Noxious Weed Control Program
• The Washington State Department of Agriculture Knotweed Control Program
• The Nature Conservancy
• 10,000 Years Institute
C. Description of specific pesticides to be used (Glyphosate and Imazapyr):
For both of these pesticides, the assessment of the length of soil half life, toxicity, and all
known potential risks is often conflicting, depending upon the source of information. These
assessments also depend on the specific formulation and the surfactants used by the
manufacturers. On Bainbridge Island the pesticides will be targeted at specific plants using
either the foliar spray or direct injection, so that there will be minimal effect on non -target
plants and minimal risk of exposure to humans. The Bainbridge Island Knotweed Working
Group supports the position that if these products are used according to the manufacturer's
instructions, environmental and human hazards will be minimized. Other methods and
products may be used according to an assessment of the effectiveness of current practices and
best available science.
Glyphosate
Description
Glyphosate is a broad spectrum, non-selective systemic herbicide used in the control of
weeds. It is transported throughout the plant where it acts on various enzyme systems,
inhibiting amino acid metabolism.
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RESOLUTION 2007-13: EXHIBIT A
Soil half-life
The MSDS sheet states that the half-life varies from 1.7 to 141.7 days. The length of soil
half-life depends on a number of conditions, such as type of soil, weather, etc. It is
strongly adsorbed to soil particles, which prevents excessive leaching and reduces uptake
from non -target plants. In water, glyphosate is dissipated through adsorption to
suspended and bottom sediments, and has a half-life of 12 days to ten weeks. Glyphosate
is degraded by microbial communities into naturally occurring chemicals including
carbon dioxide and inorganic phosphate.
Toxicity levels
The EPA classifies glyphosate as a Category 3 pesticide' and the EPA recently classified
it as non -carcinogenic in humans.
The formulations of glyphosate approved for use near aquatic systems, e.g. Aquamaster,
may only be applied by a licensed applicator.
Potential risks
Like all chemicals, glyphosate can be toxic at sufficiently high exposure levels, and
recorded toxic effects in humans following ingestion have included respiratory tract
irritation and kidney damage. Glyphosate appears to absorb poorly through the skin. In
rats and mice, acute oral LD50 (the lethal dose which causes death in half the exposed
population) is 2,000 to 6,000 mg/kg. The Bainbridge Island Knotweed Working Group
has discussed this, and the members are of the opinion that severe symptoms would only
occur in the case of a high dose due to using the product incorrectly.
ImaZMr
Description
Imazapyr is a non-selective herbicide used for the control of a broad range of weeds. It
controls plant growth by preventing the synthesis of branched chain amino acids. It is
quickly absorbed in plant tissue and can be taken up by roots: it is best used as a post
emergent herbicide.
Soil half-life
The EPA states the half life of Imazapyr is 17 months. The Nature Conservancy website
indicates a half-life from 25 days up to 141 days. Other sources vary from 2 days in
water to 49 months in soil.
Toxicity levels
The EPA classifies Imazapyr as a Category 3 pesticide.' Most sources of information
regarding toxicity indicate Imazapyr is not highly toxic if applied as directed. In the
correct formulation (Habitat) it may be used near water and is not toxic to aquatic
organisms. It may only be applied by a licensed applicator. The Nature Conservancy
states that there is a low toxicity to animals and fish, and is degraded by sunlight in
aquatic systems (half-life of 2 days).
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RESOLUTION 2007-13: EXHIBIT A
Potential risks
Imazypyr is not a known carcinogen (Center for Ethics and Toxics: www.cetos.org).
Symptoms from contact may include irritation to the eyes, skin, and respiratory system.
However, according to two sources (Center for Ethics for Toxics and Alaska Community
Action on Toxics), Imazapyr is a neurotoxin and can cause symptoms similar to
Huntington's chorea disease. The BI Knotweed Working Group has discussed this, and
the members are of the opinion that symptoms similar to those described above for
Huntington's chorea disease would only occur where there was a high dosage, which
would not happen if the product is used as directed.
D. Application
Proposed dates
Dates of application depend on the method to be used, with earlier summer applications
appropriate for foliar spray and late summer/early fall applications more appropriate for
injection. Pesticide application dates will be chosen consistent with BMPs for most
effective results.
Method of application
The proposed method of application will include direct injection and targeted foliar spray.
The application will be in accordance to the manufacturer's instructions in order to minimize
non -target effects on the environment and to minimize human exposure. Other methods may
be used according to an assessment of the effectiveness of current practices and best
available science.
Notification and Posting
Notification will be done in accordance with BIMC 16.30.060 (Public Notification).
Additional educational outreach will be implemented.
Steps to minimize risks
All applications will be done according to the manufacturer's directions by licensed
professionals to minimize any non -target effects on the environment and to minimize human
exposure.
E. Evaluation of alternatives
To provide a local example, in the summer of 2005 Bainbridge Island volunteers spent over
100 hours to cut and bag approximately 13,000 square feet of knotweed along public roads so
that city crews would not mechanically mow and thereby spread the plant. These measures
did not noticeably reduce the area affected by knotweed. Given this level of effort and its
results, it is infeasible to expect mechanical approaches to effectively control knotweed at an
island wide scale.
According to The Nature Conservancy and the Washington State Department of Agriculture,
all attempts to control knotweed using only mechanical methods have been unsuccessful
(except in a small patch of 50 stems or less with intensive mechanical methods).
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RESOLUTION 2007-13: EXHIBIT A
Integrated Pest Management (IPM) that uses best management practices, including
mechanical and chemical methods to control this highly invasive plant is the best approach
for knotweed on Bainbridge. Mechanical control along rights-of-way are only practical to
temporarily prevent encroachment into the roadway.
F. Legal requirements
All applications will be done according to local, state, and federal laws. According to
Chapter 17.10 of the RCW and Chapter 16-750 of the WAC, state law requires noxious weed
control. The Kitsap County Noxious Weed Control Board requires control of knotweed in
Kitsap County.
Footnote:
'The EPA uses three Categories to describe toxicity:
Category III: CAUTION signals that the product is slightly toxic to not acutely toxic.
Category II: WARNING signals that the product is moderately toxic.
Category 1: DANGER signals that the pesticide is extremely toxic to highly toxic
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