Cushion scale

Heavy cushion scale infestations result in the blackening of the foliage of camellia, holly, rhododendron, Trachelospermum and some other evergreen plants during the early months of the year.

Cushion scale (Chloropulvinaria floccifera) on Holly (Ilex aquifolium). Credit: RHS/Entomology.

Cushion scale (Chloropulvinaria floccifera) on Holly (Ilex aquifolium). Credit: RHS/Entomology.

Quick facts

Common name Cushion scale
Scientific name Pulvinaria floccifera
Plants affected Camellia, Ilex (holly), Euonymus japonicus, Rhododendron, Trachelospermum, Taxus (yew) and some other evergreen plants
Main symptoms Black sooty mould on the upper leaf surface in winter-spring; scale insects and white egg masses on the underside of leaves in spring and early summer
Most active All year round

What is cushion scale?

Cushion scale is a sap-sucking insect that attacks the foliage of mainly evergreen trees and shrubs, especially camellia, rhododendron, Trachelospermum, Euonymus japonicus and holly.

Symptoms

  • A heavy coating of a black, non-parasitic fungus known as sooty mould forms on the upper leaf surface. This develops over the winter months and can persist into the summer
  • Yellowish-brown, oval scale insects up to 3mm (1/8in) long can be seen near the veins on the undersides of the leaves
  • Rectangular white waxy egg masses, up to 10mm (almost ½in) long and 2-3mm (1/8in) wide, are produced by the adult scales in spring and early summer. The remains of these egg masses can persist on the foliage throughout the year

Control

Apart from the presence of honeydew and sooty mould cushion scale does not appear to adversely affect the vigour of its host plants.

Non-pesticide control

  • Sooty mould will gradually flake off the leaves during the summer
  • On small plants sooty mould can be removed by wiping the foliage with a damp cloth

Pesticide control

  • Late June-July is the best time to spray the plants as that is when the more vulnerable newly-hatched scale nymphs are present 
  • Note that dead scales can remain firmly attached to the plants. The success of any treatment can be gauged by the extent to which new growth remains free of infestation
  • 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 scale insects. These pesticides have a very short persistence and so may require reapplication to keep scale insect nymphs 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)
  • The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available
  • Follow label instructions when using pesticides
  • 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
  • Do not spray on or near plants in flower due to the danger to pollinating insects

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

Biology

  • There is one generation of cushion scale a year with eggs hatching in late June-July
  • The scales suck sap and excrete a sugary honeydew that coats the upper leaf surface, allowing sooty moulds to develop, especially during the winter
  • The level of infestation can vary considerably from year to year. In mild wet winters, infestations of overwintering nymphs may be reduced by a fungal infection


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