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. . Most of the fruits grown in gardens are hosts to at least one species of aphid.

Many of the aphids that feed on fruits have similar life cycles. They overwinter on the trees and bushes as eggs which are laid in crevices in the bark or near buds. Aphid eggs are usually shiny black, about 1mm long and ovoid in shape. They hatch in spring, as the buds begin to open, and the nymphs feed on the new growth. Aphids reproduce rapidly and their numbers reach a peak on the fruit host during late spring to early summer.

Winged aphids develop and migrate away from the fruit tree or bush in early summer, sometimes leading to the population on the fruit host dying out. The aphids spend the summer on herbaceous plants. In the autumn winged aphids are again produced which fly back to the fruit tree (winter host) to mate and lay eggs. The summer host is often a wild plant and since the aphids disperse widely when they migrate, it is not possible to control them by treating or removing the summer host.

Some aphids, for example woolly aphid, and brown peach aphid, do not have a summer host and instead remain on fruit trees throughout the year.

These aphids have many natural predators and form the basis of many food chains, they can be part of a healthy garden ecosystem. These predators often wipe out aphid colonies by mid-summer.

Apple

• Rosy apple aphid: Summer host = plantains (Plantago spp.). Leaves fruit in June-July
• Apple-grass aphid: Summer host = annual meadow grass (Poa annua). Leaves fruit in May
• Rosy leaf-curling aphid: No migration
• Woolly aphid: No migration

Cherry

• Cherry blackfly: Summer host = bedstraws (Galium spp.). Leaves fruit in June-July

Peach

• Peach-leaf rolling aphid: Summer host = clematis. Leaves fruit in May-June
• Brown peach aphid: No migration

Pear

• Pear-bedstraw aphid: Summer host = bedstraws (Galium spp.). Leaves fruit in May-June

Plum

• Plum leaf-curling aphid: Summer host = many herbaceous plants. Leaves fruit in May-early June
• Mealy plum aphid: Summer host = grasses and reeds. Leaves fruit in June-July. Can remain on plum throughout summer

Currants

• Currant blister aphid: Summer host = hedge woundwort (Stachys sylvatica). Leaves fruit in June-July
• Currant-sowthistle aphid: Summer host = sowthistle (Sonchus spp.). Leaves fruit in May-June
• Permanent currant aphid: No migration

Gooseberry

• Lettuce aphid: Summer host = lettuce. Leaves fruit in May-June
• Gooseberry aphid: Summer host = willow herbs (Epilobium spp.). Leaves fruit in May-June. Can remain on gooseberry throughout summer

Blackberry

• Large blackberry aphid: Summer host = grasses. Leaves fruit in May-June
• Scarce blackberry aphid: No migration

Raspberry

• Large European raspberry aphid: No migration
• Small European raspberry aphid: No migration

Strawberry

• Strawberry aphid: No migration

Fruit aphids sucking sap from leaves, stems and sometimes the fruits of trees. Although this can affect the plants appearance the plant's vigour and yield are in many cases not greatly reduced.

Many aphids have substances in their saliva that cause a variety of symptoms, such as stunted growth, leaf curling, distorted fruits and discolouration of the foliage.

Some virus diseases, especially of soft fruits (e.g. raspberry viruses and strawberry viruses), can be transmitted by aphids as they move from one plant to another. Infected plants may show stunted growth, leaf mottling or other symptoms.

Aphids excrete a sugary substance, known as honeydew that makes the foliage and fruits sticky and can attract ants. A black sooty mould often grows on the honeydew, which reduces the amount of sunlight reaching the leaves and can spoil the appearance of the fruit.

Fruit aphid populations are often not noticed until the plants are showing obvious signs of damage in the spring and early summer. In some cases by this time the damage is done and the aphids may have already left for their summer hosts or been consumed by predators making control measures redundant and undesirable 

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 susceptible fruits frequently so action can be taken before a damaging population has developed. On established trees and shrubs aphids can usually be considered part of the biodiversity they support, natural enemies will normally reduce numbers during 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

• The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.

  Little can be done to deal with aphids on tall trees as treatment is only likely to be successful if the entire plant is sprayed

• On fruit trees and shrubs. Overwintering aphid eggs can be destroyed by using a plant oil winter wash (organic e.g. Growing Success Winter Tree Wash). This can be used when the buds are fully dormant in November-early February on a dry frost-free day. Plant oil winter washes are less likely to be detrimental to natural enemies and can mean that spring sprays are unnecessary  
• In glasshouses it is possible to use glasshouse fumigants. Glasshouse should be sealed and instructions on the product label must be followed. Products based on the synthetic pyrethroid permethrin are available as DeadFast Greenhouse Smoke Generator, DeadFast Greenhouse Smoke Fumigator.
• 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). Permethrin is available as a smoke formulation for use in glasshouses (e.g. DeadFast Greenhouse Smoke Fumigator)
• A systemic containing the active ingredient Flupyradifurone (Provanto Smart Bug Killer) is available for use on ornamentals and selected edibles
• The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available

Follow label instructions when using pesticides. On edible plants make sure the food plant is listed on the label and follow instructions on maximum number of applications, spray interval and harvest interval.
Plants in flower should not be sprayed due to the danger to bees and other pollinating insects
Inclusion of a pesticide product does not indicate a recommendation or endorsement by RHS Gardening Advice. It is a list of products currently available to the home gardener

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