Pear-bedstraw aphid

Pear-bedstraw aphid can cause leaf discolouration and distortion on pear trees in spring.

Pear-bedstraw aphid ( Dysaphis pyri ) on pear

Pear-bedstraw aphid (Dysaphis pyri) on pear

Quick facts

Common name: Pear bedstraw aphid
Scientific name: Dysaphis pyri
Plants affected: Pear
Main cause: Sap-sucking insects causing discoloured and distorted foliage
Timing: April-July

What is pear-bedstraw aphid?

Pear-bedstraw aphid is a small sap-sucking insect that feeds on pear foliage during spring and early summer. Heavy infestations can check plant growth and can cover the foliage in honeydew.

Symptoms

Dense colonies of small (<2.5mm) 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. Heavily infested shoots show stunted growth with distorted leaves that start to turn brown during the summer.

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

Control

Non-pesticide control

  • Light infestations can be tolerated as non-pesticide measures such as manual removal of the aphid is not usually feasible
  • Aphids have many natural enemies, including ladybirds, hoverfly larvae, lacewing larvae and several parasitoid wasps which can help control populations of this insect
  • There is evidence that earwigs on fruit trees can reduce aphid numbers and they do not cause damage to the trees or fruits. Providing shelters such as flower pots loosely stuffed with hay in trees can help increase numbers

Pesticide control

  • Treatment is only feasible on trees small enough to be sprayed thoroughly
  • There is no point in spraying pear trees in late spring or summer, when the aphid damage has already occurred
  • Plant oil winter wash (considered organic e.g. Vitax Winter Tree Wash) can be applied to dormant trees to reduce the number of overwintering eggs, which in turn reduces spring colonies. Thorough application is required
  • When the foliage is emerging from the buds an insecticide can be applied to control newly hatched aphids
  • Organic sprays, such as natural pyrethrum (e.g. Bug Clear Gun for Fruit & Veg, Ecofective Bug Killer), fatty acids (e.g. Solabiol Bug Free, Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Organic Pest & Disease Control, Bug Clear for Fruit and Veg) 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 
  • More persistent insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Pest Killer) and deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer) 
  • The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available
  • Follow label instructions when using pesticides
  • Manufacturer's instructions for application must be followed for food crops. Thorough application is required and the pesticides must be applied before the aphid has caused leaf curling if there is to be any likelihood of control
  • Plants should not be sprayed when in flower due to the danger to pollinating insects
  • Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener

Download

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

Biology

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 up 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. Infestations on pear die out during the summer but there is a return migration from bedstraws in autumn when overwintering eggs are produced.


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