The spruce needleminer is found across much of the United States and Canada. In the Northeastern portion of its range, it is known to primarily utilize the host plants listed above. In the western portion of its range, it may be more commonly found on Engelmann, blue, and Sitka spruces. Adult moths are small, brown, and approximately 1/2 inch with wings spread. Their front wings have 3 irregular gray/white bands. After adult moth emergence in May and June, the females will lay groups of pale green eggs on the base of host plant needles. Eggs are laid in groups of 6-7, but up to 12 eggs per needle have been recorded (Baker, 1972). Freshly laid eggs may be found through July. Green to greenish brown larvae eventually hatch from these eggs, then proceed to cut a hole in the base of the needle where they enter and begin mining. (Caterpillars can be reddish brown, green, or greenish brown with yellow/brown heads.) It is possible that several larvae may mine a single needle. As the larvae feed, they sever dead needles which remain attached to one another by strands of silk. The needles do not contain insect frass (excrement). The frass is expelled into the webbing (nests) containing silk and dead needles. Needle mining and severing continues until the frost, at which time the caterpillars re-enter hollowed out needles and spin a silken web over the opening. This becomes their overwintering location. Caterpillars emerge again the following spring as temperatures warm. They may conduct further feeding until they are ready to pupate by approximately mid-April. At maturity, the caterpillars may be up to 1/4 inch in length. On average, each caterpillar may kill up to 10 needles. It is common for the caterpillars to become more social in the springtime, with two or more living together amongst their webs. Pupation occurs outside of the needle, within silken cocoons found within the messy nests of silk and dead needles. New generation nests may coalesce with old generation nests as the seasons progress. A similar species, the European spruce needleminer (Epinotia nanana), on the same hosts may be confused for the spruce needleminer.
The spruce needleminer prefers the older needles of their host plants, but can be found on all needles. The caterpillars tie needles together and cause needle browning. Brown needles and webbing in small clumps that are easily pulled apart are a sign of the activity of the spruce needleminer. Tiny exit holes may be visible at the base of each needle, with magnification. The feeding damage to the host is usually aesthetic and typically does not negatively impact the overall health of the host plant. As such, chemical management of the spruce needleminer may not be necessary. This may not be the case for small ornamental trees - on occasion, the entire crown of small trees may be killed. Historically, there have been cases where spruce needleminer has become a serious pest of nursery grown Picea glauca var. densata, Black Hills spruce in New York (Tashiro, 1974). For example, young ornamental trees growing on poor sites may be more susceptible to serious injury. Large trees are very seldomly killed by this insect. On large trees, the damage is usually found on the inner parts of the lower branches.
If abundant, the adult moths will fly from their infested hosts when disturbed. Moths may be particularly noticeable in the second half of June. Visually monitor for webbed together nests containing frass and mined, browned, hollow needles from approximately July and August through spring of the following year.
Prune out and destroy infested branches if practical. This will help reduce the population of caterpillars on a single tree or ornamental planting. Some suggest spraying the mined and browned needles from the host plant with a strong stream of water. In the case of syringing the needles with a hose from the host plant, some sources recommend collecting them from the ground and destroying them after (rather than leaving them on the ground in the case of moth emergence).
Knowledge of the natural enemies of the spruce needleminer has not been extensively explored. However, they are assumed to exist given that this insect's population typically does not reach severely damaging numbers. One record of a natural enemy of the spruce needleminer comes from Schaffner (1959) which includes a report of a single collected hymenopteran parasitoid in the genus Chelonus spp. Further research is necessary.
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Bifenthrin (NL)
Carbaryl (L)
Chlorantraniliprole (NL)
Chlorpyrifos (N)
Cyantraniliprole (NL)
Flonicamid+cyclaniliprole (N)
Horticultural oil (L)
Insecticidal soap (NL)
Malathion (L)
Neem oil (NL)
Pyrethrin+sulfur (NL)
Spinosad (NL)
Tebufenozide (NL)
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), acetamiprid (injection), chlorantraniliprole (soil drench), cyantraniliprole (soil drench, soil injection), and neem oil (soil drench).
When used in a nursery setting, chlorpyrifos is for quarantine use only.
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
