SBW populations are increasing in northern Maine. The Maine Forest Service captured building SBW populations in northern Maine through surveys, where roughly 3,400 acres of defoliation was recorded during aerial survey in 2024. The University of Maine Spruce Budworm lab monitored SBW larvae (L2) on tree branch samples and found populations that were at or above the outbreak threshold of an average of seven larvae per branch in northern Maine. When larval populations are at or above this threshold, an outbreak of SBW is likely to occur.
Maine timberland owners and managers in Maine formed the Maine Budworm Response Coalition (MBRC) and are working collaboratively with the Maine Forest Service, Cooperative Forestry Research Unit, and Maine Forest Products Council to reduce impacts from SBW as it builds toward outbreak conditions. The MBRC successfully advocated for funding to implement Early Intervention Strategies (EIS), an approach developed and tested by New Brunswick, Canada to reduce SBW populations below the outbreak threshold.
Aerial Spray Program – 2025
The Maine Budworm Response Coalition (MBRC), comprised of timberland owners and managers in Maine, successfully advocated for emergency funding to oversee and implement the Early Intervention Strategy (EIS) methods to reduce the rising SBW populations and protect the health of our forest ecosystems and resources, maintain wildlife habitat, and prevent impacts to our forest-based economy. The MBRC is collaborating with the Maine Forest Service (MFS), who will provide technical assistance and communications with landowners and the public regarding biology, management options, and SBW history. Additionally, the MFS will provide financial oversight and reimbursement for the state and federal funds supporting the SBW response.
MFS is working with landowners, scientists, the University of Maine, and other agencies to inform the MBRC where treatment is needed and how to best target those areas to reduce SBW populations below the outbreak threshold. To achieve this goal, the MBRC will be coordinating the administration of low-toxicity insecticides through an aerial spray program in late May through early June 2025. Roughly 240,000 acres in northern Maine with larval populations at or exceeding the outbreak threshold will be targeted.
Where is the 2025 Spray Program Happening?
The MBRC is planning aerial applications for two operational areas: (1) general location of Cross Lake and the surrounding Fish River Chain of Lakes, and (2) lands along the Quebec border, stretching from Estcourt and St. Pamphile easterly towards the St. John River.
Aerial spraying will only be applied:
- Inside predetermined areas of spruce-fir forest with SBW populations that are at or above the action threshold
- No closer than 100 ft from lakes, streams, other bodies of water and ¼ mile from identified habitat of state endangered and threatened butterflies
- In good weather (no rain or high winds) to prevent drift or unintended applications
- Using reduced-risk insecticides that only affect larvae that eat treated foliage
Insecticides containing active ingredients tebufenozide (Mimic) or Btk (Bacillus thuringiensis kurstaki, Foray) will be applied by helicopter and/or fixed wing aircraft using modern technologies to ensure accurate applications. SBW populations may require additional aerial applications over the coming years to ensure the populations do not reach an outbreak level.
To protect the public, road access in these areas will be temporarily blocked during active spray operations and until the spray application has dried – you may encounter roadblocks with the following signage. Please do not enter areas sooner than 4 hours after application.
