Plum aphids

Two aphid species can cause problems on plums, damsons, greengages and sloe. These are the plum leaf-curling aphid and mealy plum aphid.

Plum aphids

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 Severe leaf distortion in spring, whitish-green aphids on undersides of leaves, stickiness and sooty mould
Caused by Two species of sap-sucking insects
Timing April-September

What are plum aphids?

Plum aphids are sap-sucking insects that feed of the foliage of plums and other realted 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 makes the foliage and fruit sticky and allows the growth of sooty mould

Control

Non-pesticide control

  • Where possible tolerate infestations of plum aphid. Whilst infestations of leaf-curling plum aphid can be unsightly the effect on yield is limited
  • Aphids are eaten by a wide range of predators and parasites but these are not usually present in sufficient numbers, particularly early in the growing season, to prevent plum aphid infestations developing
  • 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

  • On plants small enough to be sprayed thoroughly, overwintering eggs can be destroyed by using a plant oil winter wash (organic e.g. Vitax Winter Tree Wash) when the buds are fully dormant in November-early February on a dry frost-free day. Plant oil winter washes are likely to be least detrimental to natural enemy populations and also can mean that spring sprays are unnecessary. This should reduce or eliminate any need for spraying during the growing season
  • Insecticidal sprays are less likely to be successful if leaf distortion has occurred
  • 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 that are not hidden within distorted leaves. 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), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer) and cypermethrin (e.g. Py Bug Killer). As with organic types these contact insecticides are less likely to control aphids in distorted leaves
  • The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available and may have some effect on aphids in distorted leaves 
  • 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 applications, spray interval and harvest interval. As a guide the minimum interval that needs to be left between treatment and picking the fruit is 14 days for acetamiprid, seven days for deltamethrin and lambda-cyhalothrin and one day for pyrethrum
  • Do not spray during plants 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 gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

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 infestation 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 away 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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