Dense colonies of small (<2.5 mm) pinkish grey aphids develop on the underside of the foliage in spring and early summer. Leaves at the shoot tips can become curled and yellowish and in some cases shoots show stunted growth with distorted leaves that start to turn brown during the summer. The crop and future health of the tree  however, can be unaffected. These aphids often support large numbers of predators.

The leaves can also become sticky with honeydew, on which black sooty moulds may develop. During summer populations on pear die out and the aphids migrate to bedstraws (Gallium species).

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 management 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
• 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
• 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

Pear-bedstraw aphid overwinters on pear 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 plants known as bedstraws, Gallium species, where they spend the rest of the summer. Populations on pear die out during the summer but there is a return migration from bedstraws in autumn when overwintering eggs are produced.