Giant bark aphids, as implied by their common name, are large. They reach up to 6 mm. in length, or just under 1/4 inch. Their long legs make them appear even larger. This species has short, black cornicles (two projections on either side of the end of the abdomen). Eggs are laid by the females late in the growing season, possibly into the fall, and overwinter. Eggs are elongated in their shape and orange-brown when freshly laid but eventually change in color to a shiny black. They may be found in cracks and crevices of the bark or smooth bark on smaller branches. These insects are often noted as active throughout much of the growing season, but historically become the most numerous by the late summer. These particular aphids, when present in large numbers, can cause noticeable damage to their hosts. When populations are high, twigs may be completely covered in their eggs. Occasional outbreaks of this insect have been recorded in the history of the US, such as in 1882 when they were found on sycamores over a large part of the United States (Weed, C.M. 1891).
May cause noticeable injury to the host by killing twigs and branches, particularly when populations are high, due to heavy feeding. Heavy populations are most noticeable by late summer. Giant bark aphids may also excrete large amounts of sugar-rich honeydew (liquid excrement) that can coat surfaces, including leaves, beneath where they are feeding. Honeydew then promotes the growth of black sooty mold and may also be attractive to stinging insects.
Scout the trunk, branches, and twigs on susceptible hosts for feeding aphids or overwintering eggs.
Heavily infested twigs and branches can be pruned and removed if practical. Syringing (or spraying the insects with a strong jet of water from a hose) is also sometimes suggested for aphid management.
Parasitic wasps, lady beetles, syrphid fly maggots, lace wings, and other predaceous insects feed on aphids, including the giant bark aphid, and often keep populations below damaging levels. If chemical management is occasionally deemed necessary to protect high-value plants when giant bark aphid populations are high, select options that pose the least risk to these natural enemies and beneficial insects. Preserving natural enemies is an effective form of management.
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Azadirachtin (eggs) (NL)
Beauveria bassiana (NL)
Bifenthrin (NL)
Chlorantraniliprole (NL)
Chlorpyrifos (N)
Chromobacterium subtsugae (NL)
Clothianidin (NL)
Cyantraniliprole (NL)
Cyfluthrin (NL)
Cypermethrin (NL)
Dinotefuran (NL)
Emamectin benzoate (L)
Fenpropathrin (NL)
Flonicamid + cyclaniliprole (N)
Gamma-cyhalothrin (L)
Horticultural oil (L)
Imidacloprid (L)
Insecticidal soap (NL)
Isaria (paecilomyces) fumosoroseus (NL)
Lambda-cyhalothrin (L)
Malathion (L)
Neem oil (NL)
Permethrin (L)
Pymetrozine (NL)
Pyrethrins+piperonyl butoxide (L)
Pyrethrin+sulfur (NL)
Pyriproxyfen (L)
Spinetoram+sulfoxaflor (N)
Tau-fluvalinate (NL)
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), acetamiprid (injection), azadirachtin (injection, soil drench), chlorantraniliprole (soil drench), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), emamectin benzoate (injection), imidacloprid (soil drench), and neem oil (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.
