Why is Longview in the Columbia River stink bug range while other Washington cities are not as affected?

The Columbia River Gorge was one of the first areas in the Pacific Northwest where brown marmorated stink bugs established, beginning around 2010. The Gorge's moderate climate and the movement of agricultural goods along the river trade corridor are thought to have contributed to early establishment. Longview's position at the Columbia and Cowlitz confluence places it in the core of this established Southwest Washington stink bug range, rather than at the expanding edge as in some northern and eastern Washington locations.

Are the rats near the Longview waterfront a different type than those in residential areas?

Both Norway rats and roof rats are present in Longview. Norway rats prefer ground-level and underground environments and are more common near the waterfront infrastructure and port areas. Roof rats prefer elevated travel routes and are more common in residential neighborhoods, traveling along utility lines and through trees to access rooflines. Both species can be present in the same area, but treatment approaches differ: Norway rats respond better to ground-level bait stations, while roof rats require roof exclusion and elevated entry point sealing.

Do odorous house ants really stay active in Longview through winter?

Yes. Odorous house ant activity in Longview does not fully stop in winter due to the mild Pacific Coast climate. While activity slows in December and January compared to spring and fall peaks, workers continue foraging at lower levels when temperatures remain above about 40 degrees, which is common in Cowlitz County most winters. Maintaining perimeter treatment year-round rather than pausing it in fall is the appropriate approach for Longview-area homes.

How old is the typical Longview housing stock and how does that affect pest entry?

Longview was planned and built as a company mill town starting in the 1920s, making most of the older residential housing stock 90-plus years old. That construction era predates modern tight-envelope building techniques and pest-resistant materials. Original mortar joints in brick and stone foundations have deteriorated, utility penetrations were often sealed with materials that have long since failed, and door seals have worn over decades. A professional exclusion inspection on a Longview mill town home typically identifies significantly more entry points than would be found in a comparable modern construction home.

Longview, WA Pest Control Brief

Significant pests

May through October

Peak activity

temperate

Climate

Cowlitz County

County

In short

Longview's position at the confluence of the Columbia and Cowlitz rivers places it in the Pacific Northwest's core zone for brown marmorated stink bug establishment, and the Columbia River port and industrial waterfront creates rat pressures that are higher than in comparable inland Southwest Washington cities. The 1920s mill town housing stock provides structural entry conditions that these pests exploit with efficiency.

Longview, Washington is a Cowlitz County port and industrial city at the confluence of the Cowlitz and Columbia rivers, built during the 1920s as a planned mill town. That history left the city with a distinctive early 20th-century housing stock that has aged to the point of significant structural vulnerability, and the Columbia River waterfront and port facilities sustain elevated rat populations that affect the entire city. The Columbia River Gorge corridor is one of the first areas in the Pacific Northwest where brown marmorated stink bugs established, making Longview a significant stink bug pressure zone in Southwest Washington. The mild, wet Pacific Coast climate means ants, rodents, and stink bugs are active for more months of the year than in most of the country. Odorous house ants invade homes year-round. Yellow jackets from the Columbia River bottomland grow large colonies through summer. A year-round pest management program calibrated to the Pacific Northwest environment is the standard of care for Longview homeowners.

Longview pest activity at a glance

Pest	Activity window	Local risk note
Brown Marmorated Stink Bugs	Fall aggregation September through November	Stink bugs established in the Pacific Northwest by 2010, with the Columbia River Gorge corridor being one of the first areas of establishment in the region. The Cowlitz County location near the Columbia River places Longview in the core range of stink bug populations in Southwest Washington. They are a significant fall pest in Longview's older housing stock.
Western Yellow Jackets	May through October, peak August and September	Yellow jackets are common in Longview's residential areas and in the wooded riparian habitat along the Columbia and Cowlitz rivers. Ground nests in residential yards and wall void nests in older housing are encountered regularly. The Columbia River bottomland provides extensive nesting habitat adjacent to the city.
House Mice	Year-round	House mice are year-round in Longview's mild Pacific Coast climate. The Columbia River waterfront and port operations create rodent habitat adjacent to the city's residential and commercial areas. The 1920s and 1930s mill town housing stock has accumulated many rodent entry vulnerabilities over 90-plus years.
Odorous House Ants	Year-round, most active spring and fall	Odorous house ants are the most common structural ant pest in Western Washington. They invade Longview homes year-round in the mild Pacific Coast climate, seeking food and moisture. The Cowlitz County rainfall and mild temperatures allow odorous house ant activity even in winter months when most of the country's ant populations are dormant.
Roof Rats	Year-round	Roof rats are established in the Pacific Northwest and are active year-round in Longview's mild climate. The Columbia River waterfront, the port facilities, and the Cowlitz River corridor provide elevated rat habitat. They enter homes through roofline gaps and travel overhead along utility lines and through mature tree canopies.

Columbia River Gorge Stink Bugs and Waterfront Rats in Longview

The Columbia River Gorge corridor is one of the Pacific Northwest's earliest zones of brown marmorated stink bug establishment, and Longview's position at the confluence of the Columbia and Cowlitz rivers places it in the core of that established range. Stink bugs aggregate on the older mill town housing stock in Longview each fall in numbers that have surprised residents who moved here from western Oregon or the Seattle area, where stink bug populations were established later and are somewhat less intense. Longview's Columbia River waterfront and the port facilities along the industrial waterfront sustain Norway rat and roof rat populations that are elevated compared to inland Cowlitz County. Port operations, food processing facilities, and the waterfront industrial infrastructure provide the food waste and harborage conditions that sustain large rat populations near the river. Roof rats move overhead from the port area through the city's residential streets, and Norway rats use the underground utility and sewer infrastructure beneath the commercial and industrial waterfront to extend their range into adjacent residential areas.

Year-Round Ants, Yellow Jackets, and Mice in Longview's Mill Town Setting

Longview's Pacific Coast climate means that odorous house ants are active year-round, never having a true winter dormancy period. They invade homes in search of food and moisture in every month, though activity peaks in spring and fall when colony populations are expanding or contracting. The mild winters that Longview experiences, rarely dropping below 20 degrees, allow ant foraging to continue at low levels even in December and January. Perimeter treatment programs need to be maintained year-round in Cowlitz County rather than paused for winter. Yellow jackets from the Columbia and Cowlitz river bottomlands grow large colonies in Longview's residential yards and in the wooded riparian areas adjacent to the rivers through summer. They peak in August and September, coinciding with the outdoor season on the rivers. House mice are year-round in the mild climate, unlike in colder Northwest states. The 1920s and 1930s mill town housing has structural vulnerabilities at foundations, utility penetrations, and aged door seals that mice exploit. Unlike colder climates where rodent pressure is concentrated in fall and winter, Longview sees moderate mouse activity in every season.

Your prevention checklist

Seal the building envelope of your Longview home before September to block stink bug entry from the Columbia River Gorge corridor, one of the Pacific Northwest's earliest stink bug establishment zones.
Trim trees and shrubs away from the roofline of your Longview home to cut off overhead travel routes that roof rats use from the Columbia River waterfront to residential neighborhoods.
Maintain year-round perimeter treatment for odorous house ants in Cowlitz County, as the mild Pacific Coast climate allows ant activity in every month without a true winter break.
Seal gaps in the aging foundation, utility penetrations, and door thresholds of your Longview mill town home to reduce year-round mouse entry from the Columbia and Cowlitz river corridors.
Treat yellow jacket ground nests in your Longview yard at dusk in July and August before Columbia River bottomland colonies reach maximum size in September.

Cost factors

Pest control in Longview and Cowlitz County runs $40 to $70 per month for a standard year-round program. Roof rat control programs including exterior bait stations and exclusion work average $350 to $700. Stink bug fall treatments average $100 to $200 per application.

Longview pest control, for reference

Why is Longview in the Columbia River stink bug range while other Washington cities are not as affected?: The Columbia River Gorge was one of the first areas in the Pacific Northwest where brown marmorated stink bugs established, beginning around 2010. The Gorge's moderate climate and the movement of agricultural goods along the river trade corridor are thought to have contributed to early establishment. Longview's position at the Columbia and Cowlitz confluence places it in the core of this established Southwest Washington stink bug range, rather than at the expanding edge as in some northern and eastern Washington locations.
Are the rats near the Longview waterfront a different type than those in residential areas?: Both Norway rats and roof rats are present in Longview. Norway rats prefer ground-level and underground environments and are more common near the waterfront infrastructure and port areas. Roof rats prefer elevated travel routes and are more common in residential neighborhoods, traveling along utility lines and through trees to access rooflines. Both species can be present in the same area, but treatment approaches differ: Norway rats respond better to ground-level bait stations, while roof rats require roof exclusion and elevated entry point sealing.
Do odorous house ants really stay active in Longview through winter?: Yes. Odorous house ant activity in Longview does not fully stop in winter due to the mild Pacific Coast climate. While activity slows in December and January compared to spring and fall peaks, workers continue foraging at lower levels when temperatures remain above about 40 degrees, which is common in Cowlitz County most winters. Maintaining perimeter treatment year-round rather than pausing it in fall is the appropriate approach for Longview-area homes.
How old is the typical Longview housing stock and how does that affect pest entry?: Longview was planned and built as a company mill town starting in the 1920s, making most of the older residential housing stock 90-plus years old. That construction era predates modern tight-envelope building techniques and pest-resistant materials. Original mortar joints in brick and stone foundations have deteriorated, utility penetrations were often sealed with materials that have long since failed, and door seals have worn over decades. A professional exclusion inspection on a Longview mill town home typically identifies significantly more entry points than would be found in a comparable modern construction home.

Reviewed by Marcus Reed, Lead Pest Control Technician, State-Licensed Applicator, PestRemovalUSA