Forest Services

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As spruce budworm numbers remain on the rise throughout Maine, the Maine Forest Service and its cooperators continue to track populations carefully in anticipation of an approaching outbreak.

A successful spruce budworm (SBW) monitoring program requires a multi-pronged approach and relies on the use of methods such as pheromone trapping, light trapping, overwintering larval sampling, and aerial and ground survey. At the core of the Maine Forest Service (MFS) monitoring program lies the extensive pheromone trap network throughout the spruce-fir forests of northern Maine. A permanent pheromone trap network was first established in 1992 and was made up of about 80 sites operated by MFS, J.D. Irving Ltd, Penobscot Nation Department of Natural Resources, and the USDA Forest Service. Since 2014, with the support of a large cooperator team of more than twenty land owners and managers, the pheromone trap network has grown to include more than 400 sites.

SBW is a native insect whose outbreaks cover vast regions and spread through massive dispersal flights as moths migrate from heavily impacted areas to new ones. In northeastern North America, SBW outbreaks tend to return on a 30-60 year interval and the last major SBW outbreak to directly affect Maine occurred during the 1970s-80s. Historical data tell us that Maine is due for another SBW outbreak and monitoring efforts illustrate that over the last several years, SBW population levels appear to have left the endemic or “stable” phase experienced between outbreak events. For several years now in Maine, both pheromone trap and light trap catches have been above numbers expected during the endemic phase and millions of acres of defoliation in neighboring Canadian provinces continues to encroach on the Maine border. Large in-flights of migrating moths from outbreak areas in Canada into northern Maine were well-documented in 2019. The impacts of these migration events on Maine’s forests remain to be seen.



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