UMaine Spruce Budworm Lab Map

Spruce budworm background

The Spruce budworm (Choristoneura fumiferana) is a native insect that can cause major damage to Maine’s spruce-fir forests. Spruce budworm (SBW) larvae feed on the buds and needles of fir and spruce. Usually, populations of this insect are so low that SBW is hard to find. Periodically, SBW undergoes a population outbreak and becomes so abundant that serious feeding damage occurs. During the last SBW outbreak, in the 1970s – 80s, more than 7 million acres of fir and spruce were killed in Maine and the forest products industry lost hundreds of millions of dollars¹.

1. The Coming Spruce Budworm Outbreak, Initial Risk Assessment and Preparation & Response Recommendations for Maine’s Forest Community. Spruce Budworm Task Force Report, 2016.

aerial view of fir trees in forest taken from a drone

The UMaine Spruce Budworm Lab provides population data for Maine’s forests

The UMaine Spruce Budworm Lab opened its doors in 2021 with support from the CFRU to monitor SBW populations. To predict SBW populations for the following year, tree branch samples are collected in the fall and submitted to the UMaine Spruce Budworm Lab. The Lab processes the branch samples and counts the overwintering stage of SBW, better known as an L2. L2 data is important for monitoring SBW activity and growing populations. Research has found that 7+ L2s per branch, per sample site, indicates that SBW populations have passed a threshold where natural enemies (parasites, pathogens, weather) can no longer keep populations low and stable.

UMaine Spruce Budworm Lab Map

L2 counts and models will be updated weekly as new samples are processed by the UMaine Spruce Budworm Lab. Any questions on the models should be directed to Neil Thompson, Professor of Applied Forestry at UMFK, neil.thompson@maine.edu. Additional layers are available for viewing parcel boundaries, 2023 data (Maine & Canada), and previous models. Click here to view the mapping application in a separate window. To get the most up-to-date population estimates, make sure you are viewing the most current layer.

More information on the map & L2 sampling

What do the L2 interpolation models represent?

Outputs of this model are classified into three categories: 3.5-6.5, 6.5-40.5, and >40.5 L2 per branch. Total acreage is reported for each category after erasing hardwood stands identified by remote sensing, lakes, rivers, buffers on waterbodies and streams, farm fields, and other areas without vegetation identified in the 2018/19 Crown of Maine LiDAR flight.

Color symbology for UMaine Spruce Budworm L2 Map

How are the L2 models created?

This model is an average of three interpolation processes: Inverse Distance Weighting, Empirical Bayesian Kriging, and a Radial Basis Function, using the 2024 L2 data as it becomes available and 2023 L2 data and spring 2024 field observations where updated data are not yet available. The points on the map show only the updated 2024 data, indicating where the model is most informative. This approach is based on the first step in the New Brunswick blocking process.

Don’t forget your protocol before heading out into the woods to collect your samples!
To get accurate L2 numbers, it is critical to take your sample from the mid-crown of the tree. This can be a moving target if your sample trees’ live crown ratio is low.
3 samples = 3 trees within a roughly 30-foot radius of each other. Only co-dominant or dominant trees should be sampled.
If you are sampling from a balsam fir, you need to be high enough in the crown so you aren’t getting “flat fir” samples. Foliage should be somewhat curled.
Review this short how-to video we made and share it with any of your staff who will be in charge of collecting the samples.
For questions on L2 results, contact the Spruce Budworm Lab, sprucebudworm@maine.edu.
To purchase additional samples, visit the Spruce Budworm Lab web store.

An image that shows the correct place to take a branch sample from on a tree.