Plum aphids

Two aphid species commonly occur on plums, damsons, greengages and sloe. These are the plum leaf-curling aphid and mealy plum aphid.

Plum aphids

Quick facts

Common name Plum leaf-curling aphid and mealy plum aphid
Latin name Brachycaudus helichrysi and Hyalopterus pruni
Plants affected Plums, damsons, greengage, sloe
Main symptoms Leaf distortion in spring, whitish-green aphids on undersides of leaves, stickiness and sooty mould
Caused by Two species of sap-sucking insect
Timing April-September

What are plum aphids?

Plum aphids are sap-sucking insects that feed of the foliage of plums and other related fruit trees.  

Symptoms

  • Plum leaf-curling aphid causes severe leaf distortion on the foliage of all types of plum during April to late May. Leaves that develop later are not affected, although the earlier damage often remains visible throughout the summer
  • Mealy plum aphid is active in mid- to late summer, when dense colonies of pale greenish white aphids cluster on the underside of leaves and shoot tips. This aphid does not cause leaf distortion but it excretes honeydew that can make foliage and fruit sticky and allows the growth of sooty mould
Despite appearances yield and future health of the trees is often unaffected. 

Control

Check susceptible plants frequently from early spring so action can be taken before a damaging population has developed. Once leaf distortion has occurred there is little can be done to deal with plum leaf curling aphid. 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, the plum aphids often do not affect cropping or future health of the tree
  • 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
  • Research has indicated that earwigs on fruit trees can reduce aphid numbers and in fruit trees they do not cause damage. Providing shelters such as flower pots loosely stuffed with hay in trees can help increase earwig numbers

Pesticide control

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. Treatment after leaf curling has occurred will also have limited effects. 

  • On fruit trees and shrubs. Overwintering aphid eggs can be destroyed by using a plant oil winter wash (organic e.g. Vitax 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 
  • 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. Solabiol Bug Free, 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 gardeners (pdf document)

Biology

Both mealy plum and plum leaf-curling aphids overwinter as eggs that are laid in autumn in bark crevices and around the buds. Eggs of plum leaf-curling aphid hatch at bud burst but those of mealy plum aphid hatch later in April.

Aphids feed by sucking sap from the foliage. Leaf-curling plum aphid secretes chemicals into the foliage that cause the young leaves to develop in a crumpled and distorted fashion. In this species, winged forms of the aphid develop during May and the winged adults then fly away to various herbaceous plant where they spend the summer. The population on plums dies out in late May-early June and after that time the tree produces normal foliage.

Mealy plum aphid populations can begin to build up and heavy infestations may develop during mid- to late summer. Winged mealy plum aphids develop during the summer and these migrate to various grasses and reeds.

Both species produce a winged generation in autumn that flies back to plums and other host plants to lay the overwintering eggs.


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