Rosy apple aphid is a small (2.5 mm) dull pinkish or purple-grey sap-sucking insect that feeds on apple foliage and

An immature fruit, usually small.

Dense colonies of  pinkish-grey aphids develop on the underside of the foliage in spring and early summer. Affected leaves at the shoot tips become curled and yellowish. Where the aphids have been sucking sap from the fruitlets, they prevent the fruits' normal development. These fruits often remain small with a pinched appearance around the eye end. In late summer, some branches may have normal fruits while others have only damaged fruits, reflecting the distribution of aphids on the tree earlier in the growing season.

Heavily affected shoots show stunted growth with distorted leaves that start to turn brown during the summer. The main damage is to the developing fruits, which can be severely undersized and malformed.

Aphids form the basis of many food chains and it is not unusual to have some of these animals in a healthy balanced garden ecosystem. In home gardens not all fruit are usually affected and so some aphids can be tolerated. On tall trees aphids, where control is impractical and unnecessary, aphids can be considered part of the biodiversity they support; natural enemies will normally reduce numbers by late summer.

• Where possible tolerate populations of aphids
• 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
• Check apples frequently from spring onwards so action can be taken before a damaging population has developed
• Use finger and thumb to squash aphid colonies where practical
• Some natural enemies can be purchased for use as biological control of aphids in greenhouses, including hoverfly larvae, lacewing larvae and several parasitoid wasps. More information about these can be found on the ‘aphid predators’ page.

Rosy apple aphid overwinters on apple trees as eggs that are laid in autumn in bark crevices and around the buds on the shoots. These eggs hatch in spring as the leaves begin to emerge from the buds. While sucking sap, the aphids secrete chemicals into the foliage and fruitlets, which cause the distorted growth.

Several generations of wingless aphids develop between bud burst and early summer. During June-July, winged forms of the aphid develop that migrate away to wild flowers known as plantains, Plantago species, where they spend the rest of the summer. Populations on apple die out during the summer but there is a return migration from plantains in autumn when overwintering eggs are produced.