Cushion scale

Heavy cushion scale infestations blacken the foliage of camellia and some other evergreen host plants during the early months of the year.

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 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 persists 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 early summer and the remains of these egg masses persist on the foliage throughout the year

Control

Non-chemical control

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

Chemical control

  • Late June-July is the best time to spray the plants as that is when  the more vulnerable newly-hatched scale nymphs occur  
  • Systemic insecticides containing thiacloprid (e.g. Bayer Provado Ultimate Bug Killer concentrate) or acetamiprid (e.g. Bug Clear Ultra) are absorbed into the foliage and taken in by the young scales as they feed
  • Contact sprays containing deltamethrin (e.g. Bayer Sprayday Greenfly Killer) 
    or lambda-cyhalothrin (e.g. Westland Resolva Bug Killer) can also give control if applied thoroughly to the underside of leaves 
  • Organic pesticides, based on plant oils or extracts (e.g. Growing Success Fruit & Veg Bug Killer, Vitax Organic 2 in 1 Pest and Disease Control, Bug Clear for Fruit & Veg ) or fatty acids (e.g. Bayer Organic Pest Control, Doff Greenfly and Blackfly Killer) are contact in action. They have a short persistence and thorough application to the underside of leaves is required. More frequent applications of organic pesticides may be required to deal with the scale nymphs as they hatch

Download

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

Biology

  • There is one generation 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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