Yes, spruce and fir landscape trees have been visibly defoliated in areas with high populations of SBW larvae (check the L2 populations map to see if you may be in an affected area). Remember that affected trees can still produce buds for next year even if all of the current-year foliage has been consumed; one year of defoliation is not likely to do permanent damage to a healthy tree yard. If you can, water your trees if there is a drought during or after SBW feeding to help the tree recover.  

If your landscape trees are not under or next to older/taller spruce or fir trees with high populations of SBW larvae, they are unlikely to sustain damage. Young trees that are in close proximity to spruce and fir may suffer from some defoliation, but are seldom killed, whereas trees older than 50-60 years are more vulnerable to defoliation damage. The use of insecticides with the active ingredient Btk (Bacillus thuringiensis kurstaki) can be effective if used according to the product’s label directions.

The Maine Forest Service (MFS) can help. If you can get a close up, clear picture of the pest and any damage that is occurring, that can be submitted and is helpful to confirm what pest is there and potential actions you can take. In some cases, MFS personnel can come to the property to discuss an infestation and what might be done to limit damage. Specific information from MFS related to spruce budworm can be found here. You may submit a sample of insects and diseases that are affecting your trees to the MFS, along with a description of the damage. Please use their online reporting form when you submit a sample. Mike Parisio is the lead MFS entomologist for SBW. His contact information can be found below.

Postal address: 168 State House Station Augusta, ME 04333
Physical address: 90 Blossom Lane Augusta, ME 04333
Office phone: 207-287-7094
Cell phone: 207-592-2562
Email: michael.parisio@maine.gov

The CRSF and CFRU staff are happy to help connect you, but their focus on the research side of the outbreak.

Each pest management scenario is unique and should be addressed on an individual basis. Depending on how many spruce budworm larvae are feeding, insecticide treatments may be appropriate. The insecticide used must be labeled for ornamental trees. Generally, the preferred insecticide used against the spruce budworm in this situation is derived from a naturally occurring bacterium known as Bacillus thuringiensis kurstaki (Btk). Products with an active ingredient of Btk are preferred because they are specific to caterpillars with alkaline, or basic, gut pH, like SBW. To be effective, Btk must be eaten by SBW caterpillars (it is not a contact insecticide). The timing of the application is based both on the development of new needles on the affected trees and the stage of the caterpillar. In general, we see these coincide in early to mid-June in Maine. In addition, applications should be made during calmer winds to minimize drift and ensure good coverage of the target foliage; typically in the morning or early evening hours.

Although insecticides with the active ingredient Btk can be available on store shelves, homeowners may have difficulty getting full coverage, as spruce budworm caterpillars feed on the upper and outer portions of the tree crown. Based on this and the importance of proper timing, the Maine Forest Service encourages working with a licensed pesticide applicator.

In 2025, SBW is primarily affecting far northern and western Maine (Aroostook and northern Somerset Counties). For landowners in other parts of the state, the first thing to do is to assess the location, condition, and proportions of balsam fir, white spruce, and red spruce in your forest. Woodland owners can contact a Maine Forest Service District Forester who would be able to visit your forest – this service is free. Your District Forester will likely recommend additional planning for future management, often with a private Licensed Forester. Depending on your location and the future spread of SBW, your forest may or may not be affected, and it may take years for an outbreak to reach you, if it ever does.

It is important to prepare an action plan to manage your forest, which may include timely salvaging, or pre-salvaging trees that will likely be lost through SBW mortality in advance. This is especially true in highly vulnerable pure fir or fir-spruce stands, since there are rules about clearcutting, regeneration of seedlings, and heavy harvesting in shoreland areas. Getting ahead of an outbreak in planning makes the most silvicultural and economic sense for landowners. Planning now for the future of your forest is always advisable, and the Maine Forest Service can help.

Environmental risks posed by insecticides are outlined in label language for specific products. Insecticides are reviewed and registered by US Environmental Protection Agency and must also be registered for use in the state by the Maine Board of Pesticides Control. Two insecticides that are most likely to be used to control spruce budworm populations in Maine contain active ingredients tebufenozide and Btk; both have low toxicity and are effective when applied following label directions.

Btk is a naturally occurring soil bacteria and is not harmful to humans or other mammals, bees, birds, or fish when used according to label conditions.

Mimic (active ingredient is tebufenozide) is an insect growth regulator that larvae eat. Mimic imitates a natural insect hormone that causes the developing caterpillars to molt prematurely. The caterpillars then quickly stop feeding and die. It is harmless to humans or other mammals, bees, birds, or fish when used according to label conditions.

A SBW outbreak has the potential to kill thousands of trees due to the extensive feeding damage over several years. Dead and dying trees can provide fuel for wildfire to spread, which can also reduce Maine’s air and water quality, and result in drastic changes to wildlife habitat.

SBW is a wasteful feeder, chewing needles off at the base and webbing them to the tree. When the needles brown all at once, trees appear very unhealthy, but this may not be the case. Wait until later summer or early fall to evaluate tree health. Once brown needles are washed off by summer rains, green needles are easily seen. Trees with green canopy from the top down are still in pretty good shape. Trees with no needles on the canopy top are severely stressed. If the top turns white or silver, the tree most often dies.

Because the spruce budworm outbreak will have a substantial impact on forest composition and structure over large areas, the next outbreak will likely have an influence on wildlife habitat over a long period of time. For example, mature spruce-fir stands are vital to deer wintering areas (DWA), so a decrease in DWA areas due to an SBW outbreak are likely to lead to higher winter mortality in deer (as well as impact other species associated with mature, softwood-dominated canopies such as Canada lynx). Although insecticide spraying for SBW will have little or no direct impact on lynx, snowshoe hare, or moose. That being said, snowshoe hare need cover from predators, which is best provided by regenerating young softwoods (15 to 40 years old). The interface between mature timber and regenerating softwood stands may facilitate the ability of Canada lynx to hunt snowshoe hares. On the plus side for moose, if areas are heavily salvage logged, the increased area of early successional habitat will increase available moose browse.