Pear-bedstraw aphid

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

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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?

Aphids, also known as greenfly and blackfly, are sap-sucking insects, there are more than 500 species in Britain. Pear-bedstraw aphid is a small pinkish species that feeds on pear foliage during spring and early summer. Large populations can check plant growth and can cover the foliage in honeydew, the crop is often unaffected. 

Symptoms

Dense colonies of small (<2.5mm) 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).

Control

Check pears frequently from early spring onwards so action can be taken before a damaging population has developed. Once leaf distortion has occurred there is little that can be done to control this insect, this is also true on tall trees as treatment is only likely to be successful if the entire plant can be reached. When choosing control options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section. If this is not sufficient to reduce damage to acceptable levels then you may choose to use pesticides. Within this group the shorter persistence pesticides (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.

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
  • 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

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.
This aphid does not normally affect cropping. 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. There is no point in spraying pear trees in late spring or summer, when the aphid damage has already occurred.

  • Organic sprays, such as natural pyrethrum (e.g. Bug Clear Gun for Fruit & Veg, Neudorff Bug Free Bug and Larvae Killer), fatty acids (e.g. Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Plant Guard 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
  • 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, RHS Bug and Mildew Control, 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)

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

Download

Pesticides for home gardeners (pdf document)

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 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.

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