Garden pests - Euonymus Scale

Find out what's damaging your euonymus
Image: Marcel Jancovic/Shutterstock

In large numbers, euonymus scale can devastate evergreen euonymus species. Here’s how to deal with these troublesome pests.

What is euonymus scale?

Make sure you check for infestation between May and August
Image: User:SB_Johnny, CC BY-SA 3.0, via Wikimedia Commons

The euonymus scale is a small, sap-feeding insect that feeds on euonymus species. The males are white and easy to spot, as they congregate in groups on the leaves of infested trees. The scaly females are very well camouflaged by their brown colour and favoured home on the tree bark. 

They’re most likely to be around between May and August.

How do I recognise euonymus scale damage?

Euonymus scale is visible to the naked eye
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Euonymus scale are big enough to see with the naked eye. The white males are oval shaped, measure 1-2mm long and are generally to be found hanging around on the undersides of leaves. 

Females look like brownish scales and they’re actually fixed to the spot - usually on tree bark or leaf stems. 

When the insects suck sap from the plant, they discolour the foliage, leaving yellow patches. Affected leaves will eventually drop off. 

A heavy infestation will weaken the plant, causing severe die-back and loss of vigour.

What do euonymus scale eat?

These insects feed on evergreen euonymus - and they’re particularly keen on Euonymus japonicus.

How can I control euonymus scale?

Introduce predators to your garden for a natural means of control
Image: RHS/Andrew Halstead

You’ve got a few alternatives to help control a euonymus scale infestation: 

• Encourage natural predators - our native kidney-spot ladybird (black with a large red spot on each wing case) specialises in scale insects. Encouraging more of these into your garden can help.
• Scrape them off - if you’ve got a light infestation, you can simply scrape the scales off by hand.
• Prune affected branches - if there are any branches particularly affected you can prune these out.
• Use a bug spray - sprays containing fatty acids can help control euonymus scale. But you’ll have to reapply frequently to keep on top of the problem. Spray will be most effective in June and September when there’ll be more of the vulnerable, newly hatched nymphs around.
• Spray in the winter - spray euonymus with a plant wash in the winter.

Your euonymus scale questions

Why has my Euonymus hedge suddenly died?

This does sound like a euonymus scale infestation, which particularly affects evergreen species of Euonymus, severely weakening the plant.

The male scales generally appear on the undersides of the leaves, but it is not unusual to see them on the top of the foliage. 

You may also notice larger, brownish oyster-shell coloured scales on the stems. These are the females. When scale insects first hatch they are quite mobile and crawl around the plant sucking sap until their hard scaly shells form, when they become firmly fixed to one spot. 

Males, females and juveniles may be present at the same time and they are particularly prevalent from late spring to early autumn. Read above to find ways of coping with this invader.