The snowball aphid is found from the Northeast to parts of Canada. This insect overwinters on its host plants in the form of eggs that are laid on the twigs and buds the previous fall. Egg hatch occurs at the same time as host plant buds are opening in the spring. The young, newly hatched aphids begin to feed and develop on the new buds of their host. Mature snowball aphids are approximately 2.5 mm long and ash grey or bluish white in color. They are plump and round and look like they are coated in powdered sugar. At this time of year, the mature individual is known as a stem mother, and she is capable of producing large numbers of immature snowball aphids without sexual reproduction. Young aphids (immatures) are whitish or light green in color. Feeding from the snowball aphid causes leaves to be distorted and even on occasion the leaf stems to be bent. This happens within approximately 3 weeks of budbreak. By approximately 2 months following egg hatch, all of the snowball aphids leave their viburnum hosts, presumably for a secondary host whose identity is not certain at this time. In roughly September, winged snowball aphids return to viburnum where they give rise to the sexual form of the aphid that will reproduce and lay the overwintering eggs. Eggs are dark in color and shiny. The snowball aphid (Ceruraphis viburnicola) is a different species than the viburnum aphid (Aphis viburniphila) which is present with viburnum year round, yet does not cause leaf distortion on the host. Black bean aphids (Aphis fabae) may cause leaf distortion on certain species of viburnum.
Foliage of certain viburnum hosts may become severely distorted very early in the spring. See the above preferred hosts for more information about those that are usually the most severely damaged. The feeding of the snowball aphid causes severe leaf curling on certain species. Twisted, curled, distorted, or cupped foliage may occur as a result of their feeding.
Look for evidence of leaf distortion on susceptible viburnum as soon as leaves begin to expand. On plantings where snowball aphids feed annually, consider reduced risk management options very early in the spring. Once the leaves are fully expanded and severely distorted, management may no longer be possible. The aphids will be protected within the curled foliage, and at that point the feeding damage is already done and cannot be prevented.
Doublefile viburnum (Viburnum plicatum f. tomentosum) is not susceptible to the snowball aphid. Planting resistant species or varieties in areas where this insect repeatedly causes damage to viburnum can help manage this insect without the use of insecticides.
There is very limited information available about the specific natural enemies of the snowball aphid. Perhaps the lack of information or presence of such species is due to the fact that natural enemies may not yet be very active this early in the spring.
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)
Must be managed very early in growing season, when leaves are 2 inches long. Contact insecticides may not effectively reach the snowball aphid once they are protected within the curled and distorted host plant foliage.
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.
