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Scales are limpet-like insects that feed by sucking sap from a wide range of plants, including houseplants, greenhouse plants and many fruit and ornamental plants grown outdoors. There are more than 25 species of scale insect in the UK Scale insects can weaken plants and some excrete a sticky substance (honeydew) on foliage, which allows the growth of black, sooty moulds.
There are many different species of scale insects that attack cultivated plants. These sap-sucking insect pests can weaken the growth of a wide range of plants. Many species excrete a sticky, sugary substance, called honeydew, on the leaves and stems on which they are feeding. Some species also produce white, waxy egg masses on stems and the undersides of leaves.
A wide range of ornamental plants, fruit trees and bushes grown out of doors can be attacked. Several species of scale insects are confined to houseplants or those growing in greenhouses or other sheltered places.
You may see the following symptoms:
Biological controls can be attempted during the summer in greenhouses with a parasitic wasps, Metaphycus helvolus, Encyrtus spp. and Encarsia citrina. These attack two species of scale insect, soft scale (Coccus hesperidum) and hemisperical scale (Saisettia coffeae).
The parasitic wasp is available from some mail order suppliers of biological controls.
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 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.
Beech scaleBrown scaleCushion scaleEuonymus scaleFluted scaleHemispherical scaleHorse chestnut scaleHydrangea scaleJuniper scaleMealybug Mussel scaleOrchid scaleOleander scaleScurfy rose scaleSoft scaleViburnum scaleWisteria scaleWoolly vine or currant scale
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flower28 on 26/02/2016
I have a trachelospermum jasminoides and it has a black sooty like deposit on its old growth. Looking through various possibilities I think it's a scale insect attack which is quite advanced . Can anyone confirm this. I'm going to attack it with a bug spray.
missuknight on 05/07/2015
I have several clumps of Geum Mrs Bradshaw, they have signs of scale insect infestation. As soon as I noticed I remove the affected leaves, but it returns as I expected it would. Which sort of pest spray should I use.
Dusk67 on 03/08/2014
Help. My wisteria practically died over night. Going from flowering lush green leaves to dried up brown leaves. I haven't been able to identify if it's scale insects. But digging around the route there are lots of red ants and their white eggs. Can any one advise if it could be the ants that caused the problem or something else? Raspberry bush next to the wisteria is showing same symptoms!
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