Join the RHS today and support our charitable work
Keep track of your plants with reminders & care tips – all to help you grow successfully
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Free entry to RHS members at selected times »
Reduced prices on RHS Garden courses and workshops
020 3176 5800
Mon – Fri | 9am – 5pm
Help us achieve our goals
Join the RHS today and support our charity
Adult scale insects are usually covered in waxy shell-like cover. They feed by sucking sap from a wide range of plants, including house-plants, greenhouse plants and many fruit and ornamental plants grown outdoors. There are more than 25 species of scale insect in the UK. Some scale insects can weaken host plants and many excrete a sticky substance (honeydew) on foliage, which allows the growth of black, sooty moulds.
Scale insects on bay. Image: RHS, Horticultural Science
There are several different species of scale insects that can suck the sap from garden and glasshouse plants. They range in size from less than 1mm to over 1cm in diameter. Many species excrete a sticky, sugary substance, honeydew. Some species also produce white, waxy egg masses on stems and the undersides of leaves, this can be mistaken for mealybug or woolly aphid.
Scale insects can be found on a wide range of ornamental plants, fruit trees and bushes grown out of doors. Several species of scale insects are confined to house-plants, those growing in greenhouses or other sheltered places.
You may see the following symptoms:
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
Biological control suppliers (Adobe Acrobat pdf document)
More than 25 different species of scale insects are pests in the UK and these include Pulvinaria, Diaspis, Parthenolecanium, Unaspis, Coccus species and others. They suck sap from the leaves and stems of their host plants. They are mostly 1-6mm (less than ¼in) long, although wisteria scale, Eulecanium excrescens, can be up to 10mm (about ½in), and vary in shape and colour.
All species have a shell-like waxy covering over their bodies when mature. The eggs are often laid under the protection of this shell but with the cushion scales (eg Pulvinaria species) the eggs are deposited outside the scale under a mass of white waxy fibres.
The adults are sedentary but newly-hatched nymphs crawl actively over the plant surface and spread the infestation.
Scale insects in greenhouses can breed continuously throughout the year but those species that infest outdoor plants mostly have one generation a year.
Chemical labels explained
Chemicals: using a sprayer
Chemicals: using safely and effectively
Chemicals: storing and disposing safely
Horse chestnut scale
Protect your garden
RHS statement on pesticides in horticulture
Scurfy rose scale
Woolly vine or currant scale
the RHS today and get 12 months for the price of 9
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.