Red Scale

Parthenolecanium corni

Red Scale, Brown Fruit Scale, Plum Scale, Rooidopluis (Afr.)

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Scale insects (7244837120) by Gilles San Martin (CC BY-SA 2.0)
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Parthenolecanium corni brown scale on a leaf
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Scale insects (7244837120) by Gilles San Martin (CC BY-SA 2.0)
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Parthenolecanium corni, or Brown Scale, is a pest commonly found on woody plants. Scale insects are sap-sucking true bugs who live primarily on stems; infested plants are prone to a build-up of black sooty moulds. This is a direct result of the sweet honeydew that the scale secrete.
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Traits

May reduce the vigour of plants they infect.
Food for other wildlife in the garden.

Appearance

Adults: Brown scale adults appear oval-shaped, curved, ranging from 3-6mm. Dead females can often be seen latched to tree stems and trunks, and are a leathery-brown colour. Colouration can vary depending on the plant they are feeding on, as well as what part of the plant. Generally, brown scale insects are a tan-brown but darken with age. Stages that feed on the leaves of plants are slightly yellowish-green, whereas stages on the twigs and bark are more a mottled brown.

Symptoms

Infested plants can lose vigour. Black sooty mould can begin to form on the plants' surfaces as a result of scale honeydew secretions. Honeydew may attract ant infestations, which help to protect the scale.

Activity

Diurnal

Personality

Order

Hemiptera

Family

Coccidae

Metamorphosis

Complete

Distribution

Europe, America, Oceania, Asia and North Africa

Biological treatment

It's advised for deciduous plants to apply a plant oil winter wash, which will help control overwintering nymphs at the beginning of the year. For grapevines, the loose bark should be peeled away so that the scale insects are exposed before applying any treatments.

Chemical treatment

A variety of organic sprays are available for use from UK garden centres. They tend to have shorter persistence, so must be reapplied regularly. Spray treatments are best applied early July when larvae are still newly hatched and more susceptible. Adults are much harder to target effectively due to their protective coverings. There are more persistent chemicals available on the market for use if infestations are heavier. Read labels carefully and do some research before you spray, and try to spray at the times where scale are most vulnerable. Only use chemicals as if the plant is severely damaged and worth saving. Never spray when flowers are present, to avoid harming pollinators.

Attracts

Brown scale insects are attracted to a variety of woody plants.
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Knowledge and advice

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