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 damaged by the rhododendron lacebug, Stephanitis rhododendri. This causes similar damage but is much less common than pieris lacebug and is not found on Pieris. Rhododendron lacebug has wings that are only faintly marked with a darker line across the wings near the base.

Control

Check Pieris and rhododendrons frequently from spring onwards so action can be taken before a damaging infestation 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 the damage 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.

Non-pesticide control

• Tolerate light populations of pieris lacebug
• Encourage predators and other natural enemies of suckers, in the garden, such as birds, ladybirds, wasps and ground beetles.

Pesticide control

• 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. Solabiol Bug Free, 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 lacebugs. These pesticides have a very short persistence and so may require reapplication to keep lacebug 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)
• The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available

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.

Rhododendron lacebug has a similar lifecycle.