The L2 survey is a data collection effort to determine spruce budworm populations. The “L2” is simply shorthand for “second instar larvae,” or the overwintering stage of the SBW. The SBW L2s are counted from branches sampled at a variety of plots throughout the working forests of Maine. In late fall (the collection period in Maine is generally late November through mid December), foresters collect 3 branches from each plot as well as record information on tree species, location, amount of defoliation (if any), and branch size; samples are then bagged individually and taken to lab facilities in Fredericton, New Brunswick, to be processed. The L2 numbers revealed through this process provide forest managers with data showing trends for the area under study and help to forecast budworm density for the following year, which can be used to estimate defoliation level. See our L2 Survey Maps for the latest survey results.
Life stage time line of spruce budworm as normally found in the Northern boreal forest. Illustration from W. Qin, D. Doucent, M. Tyshenko, & V. Walker, Transcription of antifreeze protein genes in Choristoneura fumiferana, Insect Molecular Biology, 16(4):423-34 · September 2007.