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2040 84th Avenue SE
Mercer Island, WA 98040
Phone: 206.275.7609
Fax: 206.275.7868
Email: miparks@mercergov.. . .
Hours: 8:30 am - 5:00 pm
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How Is Herbicide Used By The City?

How does the City decide where to spray herbicide?
As part of a larger Integrated Pest Management (IPM) strategy, non-chemical methods are prioritized in City operations, and chemicals are only used where necessary and then in concert with other weed control strategies.  The City limits herbicide usage to the control of noxious weeds and in landscape maintenance situations that would otherwise overwhelm available labor resources. City staff continually explore ways to reduce herbicide usage further. As a result, the City and its contractors use a very small amount of herbicide annually – herbicides are generally used in much greater quantities by Island homeowners for weed control on private property.
Does the City spray blackberries?
The City does NOT apply Roundup (herbicide) or any pesticides to blackberries that are allowed to flower or fruit. 
In the rare instance that the City needs to control blackberries with herbicide, staff first ensure that all flowering/fruiting stems are cut off and removed from the site so that they cannot be harvested by berry-pickers.  In most instances that warrant herbicide use, the blackberry canes are cut to the ground and only the freshly cut stem is treated with herbicide.   
Does the City use Roundup with POEA?
No.  When the use of glyphosate (the active ingredient in Roundup) is the best fit for the target species, the City uses an aquatic formulation of glyphosate that contains no surfactants.  A surfactant is a chemical additive to herbicides that helps the herbicide stick to the leaves, which increases a plant’s uptake.  POEA (i.e. polyethoxylated tallow amine) is a surfactant known to be harmful to aquatic organisms, including amphibians, at high concentrations. For this reason, the City has elected to eliminate the use of POEA.  In many cases, the City adds an aquatic-approved surfactant to their treatments to ensure the treatments have maximum efficacy.
Is the City required to obtains permits to apply herbicides? 
Yes, but only in certain circumstances.  In order to apply herbicides near or on open water, the City must apply for a NPDES (National Pollutant Discharge Elimination System) permit each year through the Washington State Department of Ecology (DOE).  The NPDES pesticide permitting program regulates discharges from pesticide applications consistent with Section 402 of the Clean Water Act.
This permit application requires a plan that specifies the body of water, plant species, and type of aquatic-approved herbicide that will be used.  The City is required to adhere to the permit requirements including but not limited to application practices, on-site posting requirements, reporting, and record keeping. Learn more about the Aquatic Noxious Weed Control General Permit.

Do people who apply herbicides on public land need to have any certifications?
Yes.  Any staff member who applies restricted-use pesticides or uses power equipment to apply pesticides on public land is required by state law to be a Certified Public Operator. Mercer Island staff are certified through the Washington State Department of Agriculture and required to complete continuing education training through organizations such as the King County Noxious Weed Program and the Washington State Cooperative Extension Integrated Pest Management Program.  Pesticide certification ensures that staff follow best management practices for proper use and handling of herbicides, ensuring safety of the applicator and the public, and minimizing risk or exposure to off-target species. Currently, eighteen City staff members are licensed by the state.
How does the public know when and where herbicides have been applied?
All herbicide applicators are required to follow regulations for notification on the herbicide label. The City posts signage at entrances to each treated area that includes the date, time, and chemicals applied for at least 24 hours following the application.
Are there any parks that have specific limitations on pesticide use?
Yes. The Open Space Conservancy Trust has adopted the Pioneer Park Herbicide Use Protocol, which can be found at

-Current as of March 2019


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