COURTESY OF THE MAINE FOREST SERVICE
People who spent time in the north woods of Maine in the late 70s remember smelling Christmas in July, not at a craft bazaar, but due to the damage caused by spruce budworm feeding.
In the spring of 2013, in response to observations in Canada, representatives from the University of Maine, the Maine Forest Service and Maine’s forest industry met to develop “The Spruce Budworm Task Force.” They brought together an impressive cadre, crossing many agencies and organizations, to formulate a spruce budworm response plan. Published in 2016, the plan recommended several measures, including adaptive harvest to reduce budworm impacts, expanded monitoring of populations, policy changes to allow landowner control of the response, and continued communication (sprucebudwormmaine.org). In Atlantic Canada, scientists were preparing for a novel response to this insect’s buildup (healthyforestparnerships.ca).
2020 was memorable to some because it was the first time since the early 1990s that spruce budworm caterpillars were seen in Maine by people working in the woods — the birds, small mammals, wasps, and other insects that consume this native species had been finding them all along. Still, they were so uncommon that many would think they had disappeared altogether. It was later than biologists initially thought they’d be spotted, and some had begun to question whether the changing climate, particularly warmer temperatures in late summer and fall, meant Maine had seen its last budworm outbreak.
In another turning point, heavy spruce budworm feeding damage was seen near the Canadian border in 2024. In some places, all the needles that had developed this spring were stripped. During aerial survey flights, Maine Forest Service surveyors mapped almost 3,000 acres of this damage. If the wind and the sun were right and you were in the right spot, you could smell Christmas in July.
Meanwhile, scientists in Atlantic Canada were in year 10 of using an Early Intervention Strategy that targets building spruce budworm populations to suppress outbreak development. The strategy is a landscape-scale approach that requires precise, annual monitoring of spruce budworm overwintering populations, surgical applications of insecticides to augment natural mortality factors where populations show signs of growth, and a high cost before damage is evident.
Fortunately, the insecticides available today for spruce budworm management are targeted. For successful early intervention, they need to be. The insecticide applications must add to the mortality caused by the diversity of insects, diseases and other organisms living on spruce budworm. They cannot reduce the impacts of insect natural enemies.
Researchers are seeing success in the approach. Economic models show that the upfront costs are considerably less than the anticipated revenue loss from an outbreak. Ecological research shows a robust insect natural enemy community in the treated forests. Carbon sequestration and storage and greenhouse gas mitigation outlooks are also positive.
Whether an early intervention approach will be applied across Maine’s landscape remains a question. For some, it is the only logical response, and the resources to make it happen will be found for the forests they steward. For others, resources, ownership objectives, and other factors may influence plans. Although the response to spruce budworm in Maine may include many approaches, what is certain is that spruce budworm populations in Maine have been in a building phase since 2012 and, currently, at least two broad areas of northern Maine have budworm populations poised for continued growth that meet the Early Intervention Strategy action threshold identified by Canadian scientists. The Maine Forest Service and Spruce Budworm Task Force partners remain engaged in monitoring spruce budworm populations and communicating options for preparation and response.
Stay updated about spruce budworm and other forest stressors, subscribe to our newsletters at maine.gov/foresthealth, or scan this QR code. For information specific to spruce budworm, visit sprucebudwormmaine.org.
