Ceruraphis viburnicola (Gillette)
(Information adopted from GR Nielsen, University of Vermont, 1998).
Viburnum species are attractive flowering shrubs. The Snowball, Viburnum opulus var sterilis, is an attractive, sterile, shrub with large white flowers. It is frequently injured by the early spring leaf and twig-curling snowball aphid Ceruraphis viburnicola. Twisted, curled, distorted, cupped foliage is the primary symptom. Severelyinfested plants may also have the branches bent and twisted like a corkscrew. The feeding of the aphids–sucking plant juices–causes the foliage to be distorted and, when numerous, these aphids check the early growth of the Viburnum completely.
The “mature” snowball aphid is a plump, ash grey to blueish-white aphid, appearing dusted with a white powder. These are the “stem mothers” as in the case of Green Peach Aphid. Older stem mothers are deep green or blue green, with dark appendages. The young nymphs appear whitish or very light green. The migrating forms have wings.
The snowball aphid has a complicated life history. The winter is passed in the egg stage on the twigs and buds of the Snowball. The eggs hatch about the time the first buds open in the spring. The developing aphid nymphs feed in the opening buds. The “mature” snowball aphids become asexual stem mothers, which produce large numbers of young aphids without mating. There are many overlapping generations produced in a short period of time. Within 2 months of egg hatch, all snowball aphids have developed wings and left the Viburnum, migrating to an as yet unknown secondary host plant. In September, winged migrant aphids again return to Viburnum (from wherever they go) and give birth to sexual aphid forms that produce the over wintering eggs. When the egg-laying (sexual) females are about half grown, the males appear on the shrubs. The dark, shiny eggs are soon laid about the buds and in the axils of small twigs.
Management of snowball aphid begins early–just as the buds open, when the leaf tips are 2 inch long. Repeat with a second application in 7 to 10 days. Be sure to wet all of the buds, leaves, and stems thoroughly. Contact your Extension office for current chemical recommendations.
Before using any pesticide, read the label and follow all precautions!
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