Lily beetle
An 8mm beetle of an unmistakable pillar-box scarlet, which with its larvae will strip a lily to bare stems inside a fortnight. It is the one lily problem a grower can diagnose from six feet away, and the larvae are the reason it is so often missed: they cover themselves in their own wet black excrement and read as a bird dropping or a smear of mud rather than as the thing doing the damage.
Caused by: Lilioceris lilii · also called scarlet lily beetle, red lily beetle
What brings it on
Established across most of Britain since the 1980s and still spreading. Adults overwinter in soil and leaf litter, emerge from late March, and both they and the larvae feed through the summer, so a lily can be attacked from the moment it breaks ground until it dies down.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Lily beetle
- Agriculture and Horticulture Development Board — AHDB: Ornamental bulb pests
Checked 2026-08-13
Usually seen: March, April, May, June, July, August
Preventing it
Ordered by how much difference each measure actually makes, not by how often it is repeated.
- Check lilies from late March, when the adults emerge and before any eggs have been laid. A single beetle removed in spring is a generation prevented.
source
Horticultural consensusmoderate confidence
- Royal Horticultural Society: Lily beetle — control
Checked 2026-08-13
Dealing with it once it is there
- Pick the adults and larvae off by hand and squash them. Hold a hand or a pot underneath first — adults drop and land on their backs, where the black underside makes them almost impossible to find in soil.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Lily beetle — control
Checked 2026-08-13
- Rub the orange egg batches off the leaf undersides at the same time. They are laid in short irregular lines and are far quicker to remove than the larvae they become.
source
Sourced guidancemoderate confidence
- Royal Horticultural Society: Lily beetle — biology
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.
Plant-specific guides
Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.