The life cycle of the pine bark adelgid may still not be fully understood. Spruce is used as an alternate host for this species, however the pine bark adelgid is not thought to be able to complete its life cycle on spruce. On pine, the pine bark adelgid is able to reproduce repeatedly, and all life stages are found on that host. The adelgid feeds by inserting piercing-sucking mouthparts through the host plant bark, into the phloem tissue to remove host plant fluids. The pine bark adelgid overwinters as an immature (often the 3rd instar in the northern parts of its range) which begins feeding during the first days of warm weather in the spring and begins secreting white wax over itself, which can eventually coat the entire trunk of infested trees. Adelgids themselves are black (or purple to yellow), rounded with a pointed end, with short legs. Studies in Virginia indicate that all individuals are female and reproduce parthenogenetically (Wantuch et al., 2017). Egg laying may begin in late-April, and eggs are yellow-ish in color when first laid, but darken as they age. Each female can lay up to approximately 25 eggs. This insect can be found on the trunk, branches, twigs, and the base of needles on new shoots. Crawlers hatch from the eggs and move to new locations on the plant, and may be blown to new trees on the wind. Once crawlers settle to feed, they do not move until the next instar (molt). Both winged and wingless forms of adults are formed in subsequent generations. All life stages may be found overlapping through the season. Older trees may be the most thoroughly coated with this insect, looking as if they are covered in snow. On seedlings and smaller trees, pine bark adelgids are found on new shoots or dense needle clusters. There may be five or more generations of the pine bark adelgid per year, with higher numbers of generations found in warmer climates. An interesting fact: the pine bark adelgid is home to bacterial symbionts (bacteria living in close association with another organism, often to the benefit of both) which presumably help benefit the adelgid by supplying it with nutrients (Toenshoff et al., 2014). Pine bark adelgid is an example of a native North American species which is now considered to be invasive elsewhere, such as in Russia (Shirnina, 2022).
Pine bark adelgid may be found on the bark of the trunk, twigs, and branches of white, Scotch, and Austrian pines. This insect appears as cottony masses on the trunk and undersides of branches. Occasionally found on twigs and needle bases. This insect does little damage to healthy trees and can often be tolerated. A large population of pine bark adelgid, however, coating an entire tree, can be shocking to observe. Heavily infested saplings may experience needle yellowing, stunting, or dieback. In the case of the pine bark adelgid, management on large trees may not be necessary, but smaller trees may need to be monitored and management decisions made.
Monitor closely with a hand lens to determine if population is still active. Magnification may be needed to see the insects themselves, when pulling apart the white, woolly material.
Syringing, or washing off the adelgids from host plant bark with a strong jet of water, can be a useful means of removing the insects. This may be an attractive option for dealing with this insect on older trees, if the aesthetics of a heavy infestation are an issue. This may help to remove the white, woolly material without the use of chemical insecticides, which may be unnecessary for this insect that does not cause much damage to healthy, older trees. If planting eastern white pine seedlings in an area, choose sites away from mature Austrian and Scotch pines.
Syrphid flies, lacewings, and lady beetles are all predators that may feed on pine bark adelgids. Natural enemies typically handle the adelgid population, so selection of reduced risk insecticides or avoiding the use of insecticides that will harm natural enemy populations is important. Harmonia axyridis, the introduced multicolored Asian lady beetle, may be one of the predators of the pine bark adelgid. Chilocorus (previously bivulnerus) stigma, Coccidophilus (previously Microweisea) marginata, and Leucopis simplex are also three important predators of the pine bark adelgid (Raske and Hudson, 1964).
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Chlorpyrifos (N)
Chromobacterium subtsugae (NL)
Clothianidin (NL)
Cyantraniliprole (NL)
Dinotefuran (NL)
Flonicamid+cyclaniliprole (N)
Tau-fluvalinate (NL)
Horticultural oil (L)
Imidacloprid (L)
Insecticidal soap (NL)
If necessary, dormant oil applications can be made in mid-late April between 22-58 GDDs.
When used in a nursery setting, chlorpyrifos is for quarantine use only.
Active ingredients that may be applied systemically include: Abamectin (injection), acephate (injection), acetamiprid (injection), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), and imidacloprid (soil drench).
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.
