The willow twig aphid is also sometimes called the giant willow aphid. These large (4.0-5.0-5.8 mm), gray to black aphids feed only on the twigs of willow (Johnson and Lyon, 1991) however Craighead (1950) indicated that poplar may also be a suitable host. The willow twig aphid also has several rows of black patches on its abdomen, and the body is covered in a layer of fine hairs. They also have a large, dark brown to black protrusion in the center of their back. Antennae are less than half the length of the insect's body. This species of aphid is found wherever willow is grown. No males of this species have ever been found, so it is assumed to be parthenogenetic. Females produce live young which are all genetically identical. Young nymphs develop into adults. Willow twig aphids tend to gather in groups, which can become very large in size by the late summer. Temperature and density may influence whether or not the individuals develop into alates (winged, dispersing stages). This species may be found on willow trees from July through March of the next season. This aphid is particularly cold tolerant. Parts of this insect's life cycle are not yet understood by science. If disturbed, these aphids will wave their hind legs in self defense.
Twigs and small branches of willow are fed upon by this aphid using its piercing-sucking mouthparts. The damage caused is usually minimal but its size and population numbers may cause alarm to those unfamiliar with the insect. As the insects remove host plant fluids, the willow twig aphid produces much liquid sugary excrement in the form of honeydew. This can coat host plant parts, promote the growth of black sooty mold, and be very attractive to stinging insects. In some studies, the above ground and below ground growth of willow has been observed to decline as a result of willow twig aphid feeding, and in some cases survival of infested trees has been reduced (Collins, et al., 2001a).
Search for large aphids on the twigs and small branches of willow from July through the fall and possibly again in March. This species of aphid is known to be relatively cold tolerant, and may be active earlier and later than other species. Visually monitor trees coated in shiny honeydew; check twigs and small branches.
If a twig or small branch is heavily infested with an aggregation of these aphids, it can be pruned out and destroyed. This may be helpful on smaller landscape trees if it can be done without disfiguring the plant. Syringing (or spraying the insects with a strong jet of water from a hose) is also sometimes suggested for aphid management. Otherwise healthy hosts (those without additional biotic or abiotic stressors) can typically tolerate some insect feeding. Proper planting and maintenance is essential preventative management of insect pests.
Parasitoids of this particular species have been reported from Japan (braconid wasps). Predators and parasitoids in North America need further study. One report of Harmonia axyridis or the multicolored Asian lady beetle feeding on the willow twig aphid has been made. Predators and parasitoids of aphids are common, so it is likely they exist for the willow twig aphid.
Abamectin (NL)
Acephate (NL)
Acetamiprid (L)
Azadirachtin (eggs) (NL)
Beauveria bassiana (NL)
Bifenthrin (NL)
Chlorantraniliprole (NL)
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 (eggs) (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.
