How to recognise it
The 1-2mm long female scales are usually visible as little blackish-brown, mussel-shaped ‘bumps’ stuck onto woody stems. The males are white and elongated with three longitudinal ridges. They are mainly found on the underside of leaves, causing a pale mottling of the affected leaf and dieback in young shoots.
Nymphs and mature females produce whitish, waxy scales up to 3mm long covering their relatively featureless bodies. Generally they remain static, feeding on one location only, but they occasionally move to a new site.
Breeding is asexual and can occur throughout the year if conditions are favourable. 2 or 3 young scales (small pink nymphs) are born live each day for up to 3 months and remain under the mother for a few days. They then disperse and settle on the leaf independently. They reach maturity within about 2 months in warm conditions (18-25˚C).
Why it’s a problem
Their feeding causes loss of vigour and die back in the effected stems and mottling of the foliage.
Where you are likely to find it
On Euonymus japonicus and, occasionally, on other Euonymus species. It is widespread in France and some southern areas of England.
How to deter it
Check any new plants for infestations; introduction on plant material is the most common source of scales.
How to get rid of it
The parasitic wasp Metaphycus helvolus can be used as a biological control within confined areas. The wasp lays its eggs within the immature nymph scale which develop within it.
Can be controlled chemically by spraying with a systemic insecticide such as thiacloprid, acetamiprid, imidacloprid or thiamethoxan in May to mid summer when the nymphs are active and have not yet built up their protective scales, making the chemical more effective, or any time indoors where the nymphs can hatch at any time due to the favourable conditions. A second application should be made after 2 weeks to deal with scales which escaped the first treatment.
Is it good for anything?!
Other useful information
Young nymphs are also known as crawlers.