Hellebore aphid

One of the most important pests of hellebores is a sap feeding aphid or greenfly. It can cause a lack of vigour and unsightly, sooty mould on the leaves and flowers.

Hellebore aphid (Macrosiphum hellebori) on Hellebore (Helleborus sp.). Credit: RHS/Entomology.

Quick facts

Common names Hellebore aphid
Scientific names Macrosiphum hellebori
Plants affected Hellebores (Helleborus species)
Main symptoms Whitish green aphids cluster on the flowers and foliage, which is sticky with honeydew excreted by the aphids
Most active March-April

What is hellebore aphid?

A sap-sucking aphid or greenfly that infests the flowers and foliage of hellebores in the spring.

Symptoms

  • Whitish-green aphids, 2-4mm (about 1/8in) long, sometimes form dense colonies on the underside of hellebore leaves and flowers in early spring
  • The sugary honeydew they excrete can also lead to the growth of sooty moulds on the foliage

Control

Non-chemical control

  • Squashing the aphids by hand can reduce infestations but often needs repeating as it rarely removes all aphids
  • Unfortunately aphid predators are not usually sufficiently numerous in early spring to reduce hellebore aphid infestations

Chemical control

  • Organic sprays, such pyrethrum (e.g. Py Spray Garden Insect Killer,  Bug Clear Gun for Fruit & Veg, Growing Success Fruit & Veg Bug Killer), fatty acids (e.g. Bayer Organic Bug Free, Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Organic 2 in 1 Pest & Disease Control, Bug Clear for Fruit & Veg) can control aphids These pesticides have a very short persistence and so may require several thorough applications to keep aphid numbers in check
  • More persistent insecticides include lambda-cyhalothrin (e.g. Westland Resolva Pest Killer) or deltamethrin (e.g. Bayer Ultimate Fruit & Vegetable Pest Killer) and the systemic insecticides, acetamiprid (e.g. Bug Clear Ultra) or thiocloprid (e.g. Bayer Provado Ultimate Bug Killer)
  • Aphids can also be controlled by using the systemic insecticides thiacloprid (e.g. Provado Ultimate Bug Killer) or acetamiprid (e.g. Bug Clear Ultra)
  • Plants in flower should not be sprayed due to the danger to pollinators

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biology

  • Although this aphid can be present on hellebores all year round, noticeable infestations usually only occur in early spring at flowering time
  • It is possible this aphid may also be responsible for spreading the serious virus disease known as hellebore black death

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