Viburnum scale

Viburnum scale affects Viburnum tinus and ivy (Hedera),it can result in a coating of honeydew and sooty mould. 

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Viburnum scale (Lichtensia viburni) on Viburnum tinus

Quick facts

Common Name Viburnum scale
Scientific Name Lichtensia viburni.
Plants Affected Viburnum tinus and ivy (Hedera)
Main Symptom Honeydew and sooty mould
Most Active Spring and summer

What is viburnum scale?

There are many types of scale insects encountered by gardeners, they are sap sucking true bugs. 
Viburnum scale is is only found on the foliage of Viburnum tinus and ivy (Hedera)

Adult females are flat, oval, pale yellow and up to 4mm long. Males are 2.5mm long white and elongate oval. In May-June the females become covered with a white fluffy wax coating amongst which the eggs are laid. The crawlers hatch from the eggs in late June. 

Symptoms

Apart from the presence of the insects and the white fluffy eggs masses (in spring) the main symptom is the presence of honeydew on which sooty mould often grows.

Symptoms are superficially similar to cushion scale, however that species rarely occurs on viburnum or ivy.

Control

Viburnum scale insect can be difficult to control, replacing severely infested plants should be considered.
Check viburnum and ivy frequently from spring onwards so action can be taken before a damaging population has developed. When choosing control options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section. If this is not sufficient to reduce this insect to acceptable levels then you may choose to use pesticides. Within this group the shorter persistence pesticides (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife than those with longer persistence and/or systemic action.
Light infestations are of little consequence and can be tolerated, but heavy attacks can be dealt with in June when the more vulnerable newly-hatched scales 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 scale insects.

Non-pesticide control

  • Where possible tolerate populations of scale insects. Well-tended healthy plants are able to tolerate infestations, although the growth of sooty mould can be unsightly.
  • Adult scales and egg masses can be removed when seen but this may not reduce large populations
  • Encourage predators  in the garden, some ladybirds, parasitoid wasps and some birds will eat scale insects

Pesticide control

The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.

  • The best time for summer spraying is in June when the more vulnerable newly hatched scale nymphs are present 
  • Organic sprays, such as natural pyrethrum (e.g. Bug Clear Gun for Fruit & Veg, Neudorff Bug Free Bug and Larvae Killer), fatty acids (e.g. Doff Greenfly & Blackfly Killer) or plant oils (e.g. Vitax Plant Guard Pest & Disease Control, Bug Clear for Fruit and Veg) can give good control of scale insect nymphs. These pesticides have a very short persistence and so may require reapplication to keep scale numbers in check. Plant oil and fatty acid products are less likely to affect larger insects such as ladybird adults 
  • Plant invigorators combine nutrients to stimulate plant growth with surfactants or fatty acids that have a physical mode of action (e.g. Ecofective Bug Control, RHS Bug and Mildew Control, SB Plant Invigorator and Westland Resolva Natural Power Bug & Mildew). These are not considered organic
  • More persistent contact-action insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Bug Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer) and cypermethrin (e.g. Py Bug Killer)
  • A systemic containing the active ingredient Flupyradifurone (Provanto Smart Bug Killer) is available for use on ornamentals and selected edibles
  • The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available
Follow label instructions when using pesticides.
Plants in flower should not be sprayed due to the danger to bees and other pollinating insects.
Inclusion of a pesticide product does not indicate a recommendation or endorsement by RHS Gardening Advice. It is a list of products currently available to the home gardener.

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Pesticides for gardeners (pdf document)

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