Forested stands
Forest managers can lessen impacts from spruce budworm using the following forest management practices:
Promote tree species other than balsam fir. The greater the percentage of balsam fir in your stand, the greater the chances of major losses due to spruce budworm.
Perform regeneration harvests in balsam fir-dominated upland stands when they are around 45 years old.
Thin younger white spruce stands before outbreaks (evaluate spruce stands for thinning at about 30 years of age). Do not thin during outbreaks or periods of excessive drought. Perform regeneration harvests around 60-70 years of age, depending on the site index.
Consider final harvest for any spruce-fir stands that have sustained two consecutive years of budworm defoliation. Harvesting a site after two consecutive years will maximize site restoration potential and timber value.
Any fir-dominated stand that sustained heavy defoliation for 5 or more consecutive years presents a more severe wildfire risk 5 to 8 years after trees die. A clean-up harvest to remove dead trees will reduce this fire risk.
Insecticide spraying is generally not advisable in Minnesota for older spruce-fir stands. Spraying can prevent serious defoliation for any given year if done properly, but any fir-dominated stand over 40 years of age will continue to be susceptible to infestation each year. The key is to diversify the forest to make it less susceptible to budworm.
Yard trees
You can spray high-value yard and woodlot trees with Bacillus thuringiensis variety kurstaki (Btk), a microbial insecticide that kills caterpillars that eat it. However, spruce budworm begins feeding at the tops of trees, so effective Btk application that reaches upper foliage can be difficult for homeowners. For assistance in treating your trees, you can search a list for commercially licensed pesticide applicators in your county.
Because spraying pesticides is expensive in terms of both time and labor, keeping trees healthy with proper watering, mulching, thinning, and root protection is your best defense against most insect and disease damage, including spruce budworm.
Other sources of information
Spruce Budworm Management for Homeowners
Eastern spruce budworm - UMN Extension
Spruce budworm - Government of Canada