The use of pesticides is not a primary control method for pest issues and is limited to the control of noxious weeds and stinging insects. Per the Integrated Pest Management policy, the use of chemical controls requires prior approval and 48 hours of no rainfall in the forecast following application. Alternative methods of control must also be documented before the use of pesticides is approved.

Noxious Weeds

The following noxious weeds are currently being treated with the use of pesticides to control/eradicate populations:

Poison Hemlock

This class B noxious weed is required to control on public lands and rights-of-way. Poison Hemlock is seen in various locations, primarily west of 8th Ave NW. Mechanical control efforts (hand pulling, mowing) have proven ineffective and chemical control was approved in spring of 2023. Treatment will occur as the weather allows in March and April to prevent plants from reaching the flowering stage. Seeds can remain viable for up to 5 years and treatment will occur as needed to gain control of this rapidly spreading weed.

Shiny Geranium

This class B noxious weed is required to control on public lands and rights-of-way. There is a limited population of Shiny Geranium in the city but it is slated for chemical control in the spring of 2024.

Knotweed

While an unregulated class B noxious weed, knotweed’s aggressive growth requires several cutbacks per year in sensitive areas. Treatment has occurred mostly in trail access points and other areas where visibility of traffic and/or pedestrians is impeded. Additional treatments along waterways have been approved which were completed by contractors within Ballinger Open Space and Paramount Open Space. King County also treated knotweed at the Edwin Pratt Park property ahead of future site development.

We continue to monitor knotweed populations and there are additional efforts to remove knotweed from the Thornton Creek watershed.



If treatment has been approved, the following sign(s) will be posted 24 hours before application and removed 24 hours following application. This is the only sign approved for designating city treatment. Any additional signage not approved by city representatives will be removed by city staff to avoid unnecessary confusion as to if/when treatment will occur.

 

6.7.1 – Signs

Small freestanding informational signs displaying the City's logo shall be posted and include the following information: 

• Date and time of planned application,  
• Location within the site to be treated,
• The pest to be controlled, 
• The pesticide used,
• A department contact name and phone number to call for more information, and 
• Small colored flags shall define the area to be treated.

Stinging Insects

Yellow Jackets and paper wasps are predatory insects that prey on garden insects and help control their populations.  To minimize the impacts on beneficial pollinators, not every hive reported will be treated or eradicated.  Treatment will be conducted if a hive is verified and meets the following conditions:

• Close proximity to high-use areas such as picnic shelters and playgrounds
• Close proximity to heavily used sidewalks, pathways, or trails

Reports of hive activity will be investigated within 2 business days.  If treatment meets the above-listed criteria, it will be treated within 24 hours and a sign (shown above) will be placed notifying the public of the treatment time.  If a hive is verified but does not meet the necessary treatment criteria, a sign will be placed to notify the public of an active hive.