What is pieris lacebug?

Pieris lacebug is a small (3-4mm long) sap-sucking insect with wings marked with a lace-like pattern. It can be responsible for causing pale mottling most notably on the leaves of Pieris and Rhododendron.

Symptoms

Look out for the following symptoms of pieris lacebug on Pieris and Rhododendron;

• The foliage develops a coarse pale mottling on the upper surface and by late summer the leaves can have a bleached whitish yellow appearance
• Heavy attacks may cause leaf drop on Pieris
• The underside of affected leaves is discoloured with brown excrement spots
• Adults, nymphs and cast skins may be seen on the lower leaf surface
• The adults are black insects, 3mm long, with wings that are held flat over the insect’s body. The wings are transparent with a broad black X-shaped marking
• The nymphs are wingless and have spiny blackish brown bodies

Note that rhododendrons can also be attacked by the rhododendron lacebug, Stephanitis rhododendri. This causes similar damage but is much less common than pieris lacebug and does not attack Pieris. Rhododendron lacebug has wings that are only faintly marked with a darker line across the wings near the base.

Control

Non-pesticide control

• Light infestations can be tolerated 
• Heavily damage branches can be pruned after flowering 

Pesticide control

• Treatment is best carried out in early summer when newly hatched nymphs are present but further treatment later in the summer may also be required
• 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 some control. These pesticides have a very short persistence and so may require reapplication to keep lacebugs 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
• Plants in flower should not be sprayed due the danger to pollinating insects
• 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

Download

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

Biology

Pieris lacebug overwinters as eggs that are inserted into the leaf veins but adult insects can persist on the foliage until mid-winter.

The eggs hatch in May and the nymphs initially cluster together on the underside of leaves. They later disperse and reach the adult stage by mid to late summer.