Pests to know in Portland
Termites in Portland
OSU says Pacific dampwood termites and western subterranean termites damage structures in the Pacific Northwest. Dampwood swarmers leave nests in late summer or fall.[4]
Invasive species reported here
- Japanese beetles were first detected in Oregon in 2016, when 369 were trapped in northwest Portland. The Oregon Department of Agriculture began an eradication effort in 2017.[6]
- Emerald ash borer was first found in Oregon in 2022 at a Forest Grove school. A later southeast Portland detection put all of Multnomah County inside the EAB quarantine zone.[7]
Pests local experts flag
- Floodwater mosquitoes such as Aedes vexans lay eggs near flood-prone areas like Government Island, Oaks Bottom Wildlife Refuge and Smith and Bybee Lakes, usually in spring.[2]
- In Portland, persistent rat holes in a parking strip, under the sidewalk or in a front yard can mean a broken sewer line, and Vector Control can refer residents for a city dye test.[3]
Climate
Central Portland (ZIP 97204) is in USDA plant hardiness zone 9a, where the average coldest winter night is 20 to 25°F.[10]
Public agencies that handle pests
- Multnomah County Vector Control handles rat and mosquito control in Portland, working under authority granted by Oregon Revised Statute 452.[1]
- Multnomah County says mosquitoes and rats are the most common disease vectors in the county.[1]
- County Vector Control does not exterminate, but it offers free rodent property inspections, free snap traps and advice to residents.[3]
Local rules and responsibilities
Hiring a licensed company
Oregon requires an Oregon Department of Agriculture pesticide license for anyone who owns or runs a business that applies pesticides to someone else's property.[8]
Free local help
OSU Extension notes that termite treatments for Oregon homes are often done only at the pre-construction phase, and that wood touching soil gives termites a path into a structure.[5]
Through the year
- Spring to Summer
- Multnomah County residents can get free mosquitofish for ornamental ponds or unused pools from May 15 to August 30, picked up at the county's North Portland office.[2]
- Summer
- Each summer, ODA's Insect Pest Prevention and Management Program surveys for pests not known to be established in Oregon, such as spongy moth, Japanese beetle and emerald ash borer.[9]
Sources
- Multnomah County Vector Control, “Vector Control & Code Enforcement.” www.multco.us/vector (accessed 2026-10-06)
- Multnomah County Vector Control, “Mosquitoes.” multco.us/info/mosquitoes (accessed 2026-10-06)
- Multnomah County Vector Control, “Rats.” multco.us/info/rats (accessed 2026-10-06)
- Oregon State University Extension Service, “Termites.” solvepestproblems.oregonstate.edu/insects-spiders/termites (accessed 2026-10-06)
- Oregon State University Extension Service, “How can I prevent termite infestation?.” extension.oregonstate.edu/ask-extension/featured/how-can-i-prevent-termite-infestation (accessed 2026-10-06)
- Oregon State University Extension Service, “Japanese beetles in Oregon (EM 9158).” extension.oregonstate.edu/catalog/em-9158-japanese-beetles-oregon (accessed 2026-10-06)
- Oregon Department of Agriculture, “As expected, emerald ash borer has been found in multiple new sites this summer, including Portland.” apps.oregon.gov/oregon-newsroom/OR/ODA/Posts/Post/As-expected-emerald-ash-borer-has-been-found-in-multiple-new-sites-this-summer-including-Portland (accessed 2026-10-06)
- Oregon Department of Agriculture, “Explore Licensing Requirements.” www.oregon.gov/oda/pesticides/licensing/Pages/license-requirements.aspx (accessed 2026-10-06)
- Oregon Department of Agriculture, “Current Projects.” www.oregon.gov/oda/ippm/survey-treatment/Pages/default.aspx (accessed 2026-10-06)
- USDA ARS and PRISM, via phzmapi.org, “Plant hardiness zone for ZIP 97204 (2023 USDA map data).” phzmapi.org/97204.json (accessed 2026-10-06)
- National Pesticide Information Center, “State Pesticide Regulatory Agencies.” npic.orst.edu/reg/state_agencies.html (accessed 2026-10-06)