Botanic Gardens Trust, Sydney, Australia

Azalea Lace Bugs - fact sheet

The Azalea Lace Bug (Stephanitis pyrioides), an insect originating from Japan, is a signicant pest of azaleas and rhododendrons in many regions of the world where these plants are cultivated. The bug especially attacks plants growing in sunny, exposed situations.

Symptoms of lace bug attack

The feeding activity of every stage of the lace bug life cycle produces a widespread grey-whitish/silvery mottling on the upper surfaces of the leaves, similar in colour but coarser in texture to that caused by spider mites. Adult and juvenile lace bugs feed on the undersurfaces of azalea and rhododendron leaves. The mottling is usually so severe that leaves that have been attacked are permanently disfigured. Leaves will die and fall from the plant well before their time. Sticky brown patches or ‘varnish’ (excretory products of the lace bugs) appear on the undersides of the leaves. The Azalea Lace Bug is widespread throughout Australia.

Life cycle

The lace bug has at least two (and possibly four) generations per year in Australia. Adults reach 4-6 mm in length. They have clear, heavily veined wings - hence the insects’ common name. Juvenile lace bugs are wingless, spiny, have long antennae relative to their body length, and have a black and tan mottled colouring giving them an overall dark appearance.

There are probably five nymphal instars. Nymphal moult skins often remain stuck to lace bug varnish on the undersides of leaves. Lace bugs overwinter in the egg stage, hatching when conditions improve for them in the sping. Eggs are inserted into the mid-vein on the underside of the azalea or rhododendron leaf as they are laid. They have a brown protective covering which hardens on contact with air.

Control

Lace bugs are particularly difficult to control. There is currently no known effective biological control agent (e.g. a parasitic wasp). There are some pesticides that are registered for the control of this pest. Speak to your local nursery in regards to this.


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Plant Disease Diagnostic Unit
Royal Botanic Gardens & Domain Trust
Mrs Macquaries Rd
Sydney NSW 2000
Telephone: (02) 9231 8186
Facsimile: (02) 9241 1135
Email: pddu@rbgsyd.nsw.gov.au