Includes Hellebore aphid (Macrosiphum hellebori)
Pest description and damage Several species of aphid are reported from hellebore. The most common is hellebore aphid, a whitish-green aphid that measure 0.08 to 0.16 inch in length and forms dense clusters on the leaves, stems, or flowers, sometimes forming dense colonies. Aphids are often visible, but sometimes are on the undersides of the leaves. So plants should be checked from time to time. Damage includes abundant honeydew and sooty mold or blackening of leaves, or viruses transmitted when the aphids feed.
Biology and life cycle The aphids are reported to overwinter as eggs, or as adults, and hatch in early spring. When the egg hatches, the aphid is called a stem mother. After maturing, she gives live birth to the young. They, in turn, mature and birth more live young. In this way, there may be waves of aphids of different sizes.
Monitoring Watch for signs of aphids: honeydew, sooty mold and the white shriveled caste off aphid exoskeletons, or for ants that are harvesting the honeydew. Syrphid fly larvae are found munching on the aphids in the spring. Often natural enemies and ants are noticed even before the aphids are seen. Aphids are partial to succulent new growth. They are common in spring, but are reported in fall and winter as well.
Hosing off aphids with plain water can work where plants are potted or isolated in the landscape.
Releases of lacewing larvae may have some success depending on the size of the aphid population.
See Table 1 in:
Chemical Control of Landscape Pests
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