How can I tell if I have a spruce budworm infestation?
First confirm that you are looking at a fir or spruce tree, then look at the pattern of needle loss. In general, spruce budworms will feed on the upper and outer portions of the tree on the parts of twigs that developed in the current year (the outermost part of the twigs).
There are other insects that will defoliate spruce and fir, and damage from diseases can also be confused with spruce budworm damage. Examples include the yellowheaded spruce sawfly on spruce, hemlock looper on fir and white spruce, balsam fir sawfly on fir, needlecasts of spruce and fir, and Delphinella shoot blight on fir.
When in doubt, submit a report, including a description of the situation and a high resolution photo (damage, caterpillar, pupa or moth, depending on time of year), to the Maine Forest Service. The report form can be accessed here.
I think I have spruce budworms in my trees or damage from SBW – who do I contact?
The Maine Forest Service 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 on-line 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.
What is the L2 survey and data analysis?
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 forests of Maine. In late summer (the collection period in Maine is generally September through March), foresters collect 3 branches from each plot as well as record information on tree species and location. Samples are then bagged individually and taken to the Spruce Budworm L2 lab at the University of Maine in Orono, 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 spring, which can be used to estimate defoliation risk. See our L2 Survey Maps for the latest survey results.
How are L2 samples collected and analyzed?
Each fall, the Maine Forest Service and the Cooperative Forestry Research Unit (CFRU) at the University of Maine work with forestland owners around the state to collect sample branches from balsam fir trees for spruce budworm stage 2 larvae (SBW L2) analysis. These branches are chopped and washed in buckets, then residues are transferred to gridded filter paper discs where the SBW L2 are counted. The information garnered from these efforts provides information on spruce budworm population trends.
Does spruce budworm attack landscape trees?
Unless landscape trees are under or next to older/taller spruce or fir trees, 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. Spraying is effective protection if concerned. Trees older than 50-60 years are more vulnerable to defoliation damage. If budworm is detected, spraying is recommended for foliage protection.
How will defoliation affect my local area trees?
The budworm 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.
What is the best management options for a spruce-fir lot in western Maine?
First thing to do is to assess the location, condition, and concentration of high-risk species in your stand to prepare an action plan to salvage or pre-salvage trees that will likely be lost through SBW mortality. Getting ahead of the outbreak in planning makes the most silvicultural and economical sense.
Are insecticide treatments safe for the environment?
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 Maine Board of Pesticides Control. Insecticides must be applied in compliance with label language and state regulations, when applied as approved the risks are reduced.
Two pesticides that are most likely to be used to control spruce budworm populations in Maine are:
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.
When the best time of year and best time of day is to spray spruce to protect them from the spruce budworm?
Each pest management scenario is unique and should be addressed on an individual basis. Generally speaking however, the preferred insecticide used against the spruce budworm is a naturally occurring bacterium known as Bacillus thuringiensis (Bt). It is preferred because it is specific to Lepidoptera larvae, like SBW, and naturally photo-degrades over time. Bt must be applied to needles and physically ingested by SBW larvae while they’re feeding to be lethal (not a contact insecticide), so the timing of application is linked to the active feeding period (peak activity mid-May to Mid-June in Maine, with younger larvae being more susceptible).
As with all insecticides, application must adhere strictly to the guidelines provided on the chemical label. Usually SBW is only treated during outbreaks and on a grand scale, but there are also insecticides with the active ingredient BT readily available to homeowners interested in treating ornamental trees in an outbreak area. The timing of application is always most effective during times that minimize drift and ensure good coverage directly to the foliage. This means avoiding excessive breeze, heat, and moisture, usually coinciding with morning or evening hours.
For a wealth of additional information on SBW in Maine, please have a look at the Maine Forest Service SBW page here.
What will the economic impact of an outbreak look like for the southern part of the state?
Although an infestation will not likely have a huge impact on the trees in southern Maine, the potential economic impact could be quite strong. Markets will directly impacted in the northern and western areas of the state will have a ripple effect in southern areas.
Will moose, deer, lynx and other mammals be affected by the SBW?
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.
Are there any public forums on spruce budworm scheduled in Maine?
Many organizations may hold information sessions about spruce budworm. Some opportunities can be found in our calendar, but others may only be advertised by the organizers. If you wish to host a public forum, we may be able to help you find a presenter, please see our Presentation Request form under Resources.