The Maine Forest Service and the University of Maine Spruce Budworm Lab monitor spruce budworm (SBW) populations in Maine and the northeast to detect potential outbreaks before they happen. Survey and monitoring methods in 2024 identified approximately 307,000 acres in northern Maine with SBW populations reaching outbreak levels, 240,000 of which were treated. When SBW populations are elevated, natural enemies can no longer keep the SBW populations low and stable. 

In the spring of 2025, the Maine Budworm Response Coalition (MBRC) followed Early Intervention Strategy (EIS) to apply targeted insecticides to affected areas that could prevent an outbreak, maintain tree health and water quality, conserve natural enemies, and maintain the diversity of caterpillars in treated stands. After the EIS approach, treated sites experienced a ~95% decline in SBW populations while untreated sites experienced an expected increase in SBW populations. Untreated acres in 2025 were mainly comprised of small landowners and the Maine Forest Service has been working with these landowners to add their lands to the spray program planned for 2026. 

Survey and monitoring continued throughout the summer of 2025, showing an ongoing reduction in SBW populations and confirming high levels of SBW natural enemies in treated areas as well as untreated buffer zones around treated areas. The MBRC plans to implement EIS in areas with elevated L2 populations, approximately 74,000 acres, again in late spring 2026. More information on the 2026 Aerial Spray Program will be available this spring.