Aphids are sap-sucking true bugs. They range in size from 1 to 7mm (¼in or less) long. Some aphids are known as greenfly or blackfly, but there are species that are yellow, pink, white or mottled. There are more than 500 aphid species in Britain. Some feed on only one or two plant species, but others can be found on a wide range of plant hosts. Many have lifecycles that involve more than one host plant. Almost any plant can be a host to aphids, including ornamentals, vegetables, fruits, greenhouse plants and houseplants. More information on aphids. 

Hellebore aphid is whitish green and only found on hellebores it is present throughout the year, although colonies are usually only noticed in spring.
 

• 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 lead to the growth of sooty moulds on the foliage
• This species of aphid is only found on hellebores

Aphids form the basis of many food chains in the garden and it is not unusual to have some of these animals in a healthy balanced garden ecosystem. Check hellebores frequently from early spring onwards so action can be taken before a damaging population has developed. On established plants aphids can usually be considered part of the biodiversity they support, natural enemies will normally reduce numbers before summer. When choosing management options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section and avoiding pesticides. Within pesticides the shorter persistence products (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife than those with longer persistence and/or systemic action. Pesticide treatments are likely to kill natural enemies and are only likely to be successful if the entire plant can be reached.

Non-pesticide control

• Where possible tolerate populations of aphids, they form an important part of many food chains and can be part of a healthy garden ecosystem
• Use finger and thumb to squash aphid colonies where practical
• Encourage aphid predators in the garden, such as ladybirds, ground beetles, hoverflies, parasitoid wasps and earwigs. Be aware that in spring aphid populations often build up before natural enemies are active in sufficient numbers and then give good control

Pesticide control

• Organic sprays, such as natural pyrethrum (e.g. Bug Clear Ultra 2, Neudorff Bug Free Bug and Larvae Killer) or plant oils (e.g. Vitax Plant Guard Pest & Disease Control, Bug Clear Fruit & Veg, Vitax Rose Guard) can give good control of aphids. These pesticides have a very short persistence and so may require reapplication to keep aphid numbers in check. Plant oil and fatty acid products are less likely to affect larger insects such as ladybird adults
• Plant invigorators combine nutrients to stimulate plant growth with surfactants or fatty acids that have a physical mode of action against aphids (e.g. Ecofective Bug Control, Growing Success Bug Stop, Rose Clear 3 in 1 Action SB Plant Invigorator and Westland Resolva Natural Power Bug & Mildew). These products contain some synthetic ingredients and so are not considered organic
• More persistent contact-action insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer) and cypermethrin (e.g. Py Bug Killer)
• A systemic containing the active ingredient Flupyradifurone (Provanto Smart Bug Killer) is available
• The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available

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Pesticides for gardeners (pdf document)

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