Lace bug
A small flat sap-feeder with clear, lacy wings, feeding on the undersides of rhododendron and pieris leaves. The upper surface goes coarsely yellow-mottled and the plant looks starved or scorched; the answer is on the other side of the leaf, where the insects sit among shiny black tarry spots of their own excrement.
Caused by: Stephanitis rhododendri and Stephanitis takeyai · also called rhododendron lace bug, andromeda lace bug
What brings it on
Worst on plants in full sun and dry soil, which is the reverse of what the mottling suggests — a rhododendron in the shade it prefers is far less often attacked than one baking against a south wall.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Rhododendron lace bug
- Plant Finder — Missouri Botanical Garden: Lace bugs
Checked 2026-08-13
Usually seen: May, June, July, August, September
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Site rhododendrons and pieris in dappled shade with a mulched, moisture-retentive root run. The siting that suits the plant is also the siting that suppresses the pest.
source
Sourced guidancemoderate confidence
- Royal Horticultural Society: Rhododendron lace bug — control
Checked 2026-08-13
Dealing with it once it is there
- Turn several leaves over before doing anything. The mottling persists on damaged leaves long after the insects have gone, so treating a plant on the upper-surface sign alone routinely treats damage that finished last summer.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Rhododendron lace bug — control
Checked 2026-08-13
- Damaged leaves do not recover their colour, so judge whether it is working by the NEW growth rather than by the leaves that first prompted the question.
source
GrowingHQ editorial positionhigh confidence
A judgement about how the reader will assess the outcome, not a horticultural claim about the insect.
- GrowingHQ editorial synthesis — GrowingHQ
Checked 2026-08-13
What it affects
On sprays and treatments
GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.