State Confirms Spongy Moth Activity in Lakewood, Prompting Spring Aerial Treatment Plan

State agriculture officials plan to spray portions of Lakewood this spring after monitoring teams confirmed the presence of the invasive spongy moth, an insect known for defoliating hundreds of tree species. While the activity detected so far is confined to Pierce County, Washington’s eradication efforts carry implications for forest health across the region, including Southwest Washington.

According to information published by the Washington State Department of Agriculture (WSDA), staff identified five adult spongy moths in the Lakewood area during 2025 monitoring, following the discovery of 10 caterpillars the previous year. WSDA identifies the insect, Lymantria dispar dispar, as a destructive non‑native species capable of feeding on more than 300 types of trees and shrubs. Federal guidance from the U.S. Department of Agriculture, available at its spongy moth information page, warns that the pest spreads easily when egg masses are transported on firewood, outdoor equipment, and other movable surfaces.

In public comments reported by The News Tribune, WSDA communications consultant Karla Salp said that all significant damage comes from the caterpillar stage, which consumes new foliage each spring. Adults, she noted, do not feed. The agency aims to eliminate the population before it grows large enough to cause cyclic defoliation, which can weaken or kill trees after multiple years.

WSDA has identified a mile‑and‑a‑half treatment zone in Lakewood, accessible through the department’s mapping link at WSDA’s posted eradication boundary map. The agency expects to conduct aerial spraying in April or May, depending on when tree leaves and newly hatched larvae emerge. WSDA uses Bacillus thuringiensis kurstaki (Btk), a biological insecticide routinely employed in moth eradication projects. According to the materials cited by The News Tribune, Btk is considered low‑risk for people, pets, and non‑target species such as bees, ants, birds, and fish.

Residents in the Lakewood area are likely to see a small aircraft during the application period. WSDA notes that contact with caterpillars may cause skin irritation in some individuals, and heavy accumulations of droppings can create localized nuisances.

Although the current detections remain small, eradication efforts elsewhere in Washington demonstrate that early intervention is key. Southwest Washington counties, including Cowlitz County, fall within the state’s broader surveillance network. Monitoring traps typically go out each summer, and past programs have shown that localized outbreaks—if left untreated—can spread along travel corridors such as Interstate 5.

WSDA encourages residents statewide to report suspect sightings. The department’s guidance and reporting instructions are available through its invasive moth portal at WSDA’s identification page. Individuals in the Lakewood treatment area can sign up for application notices through WSDA’s alert system, linked at the agency’s 2026 eradication page.

Why this matters for Southwest Washington

Even though this year’s eradication zone is north of Cowlitz County, spongy moths are known to spread through human movement of infested materials. State and federal agencies describe the species as one of the most significant forest pests in North America, and Washington conducts statewide monitoring to prevent establishment. Local forests, parks, and urban tree canopies could face long‑term impacts if the insect gained a foothold in the region.