The giant willow aphid is medium brown to dark brown with several rows of black patches on the body. This aphid is also covered with numerous fine hairs, which can be seen with magnification and provide a grayish-golden luster to the abdomen. A large dark brown projection is found in the center of the back of the insect. Antennae of the giant willow aphid are less than half the length of the body. Giant willow aphids, as their name implies, are quite large with a body length of 5.0-5.8 mm or just under 1/4 of an inch. This insect may also be referred to as the willow twig aphid. They reproduce using parthenogenesis, or asexual reproduction. No males have ever been found in their populations, and females lay viable eggs. Eggs hatch into nymphs, which are slightly smaller than the adult insects. The life cycle of this aphid is not entirely understood. They may be noticeable by mid-summer and are often most abundant in the late summer or fall. This particular species may be very cold tolerant, and has been observed in the southern portions of its range on host plants into the winter months.
The damage caused by this insect is usually minimal, but its size and population numbers may cause alarm. In high populations, most 1 to 3 year old twigs may be covered by these insects. It is primarily a pest of willow or the genus Salix, however reports of this insect on poplar (Populus spp.) exist. Aphids may excrete large amounts of honeydew, or a sugary liquid excrement, which coats the surface of anything beneath the aphids and may promote the growth of black sooty mold. Honeydew is also attractive to stinging insects.
Search for large aphids on the twigs and small branches of willow. If honeydew is observed on willow, this may be a sign of the presence of this insect.
Heavily infested twigs and branches can be pruned and removed if practical, when populations are low. Syringing (or spraying the insects with a strong jet of water from a hose) is also sometimes suggested for aphid management.
Predators and parasites of the giant willow aphid are reportedly rare, perhaps because of their aposematic (warning) coloration. However, the multicolored Asian lady beetle (Harmonia axyridis) has been observed feeding on them (Aphids on World's Plants).
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)
Tau-fluvalinate (NL)
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)
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.
