Plant Problem Diagnostic
Lily Beetle: Identification and Control
The short answer
The lily beetle (Lilioceris lilii) is a bright red beetle about 8mm long with a black head and legs, found only on lilies and fritillaries. The most reliable sign of trouble is the larvae: rotund, reddish-brown grubs that hide under a coating of their own wet black excrement (frass), so they look like small blobs of bird mess on the leaves. Adults and larvae can strip a plant in a few days.
The most effective home control is vigilance and hand-picking. Check lilies and fritillaries frequently from early spring, pick off adults and squash the eggs and frass-covered larvae on sight, and act before a damaging population builds. Adults overwinter away from host plants, so there is no useful treatment outside the growing season. Once widespread in the UK, the beetle is also an established invasive pest in parts of the US and Canada.
How to identify lily beetle
Adults are bright scarlet with a black underside, head and legs, and about 8mm long. Eggs are laid in small clusters of orange-red, sausage-shaped eggs on the undersides of leaves. The larvae reach 6-8mm, are rotund and reddish-brown with black heads, and are usually completely hidden beneath their own wet black frass.
- Bright red beetle roughly 8mm long, only on lilies and fritillaries
- Larvae hidden under wet black excrement (frass) look like bird droppings
- Young larvae graze leaf undersides; older larvae eat whole leaves, petals and seed pods
Control by checking often and hand-picking
- 1Inspect from early spring — Check lilies and fritillaries frequently from early spring onwards, when adults emerge from overwintering, so you catch them before numbers build.
- 2Pick off adults — Remove adult beetles by hand. They tend to drop and land upside-down (their black underside is hard to spot on soil), so cup a hand beneath them as you pick.
- 3Squash eggs and larvae — Check leaf undersides for clusters of orange-red eggs and rub them off, and wipe away the frass-covered larvae.
- 4Keep it up — Repeat through the growing season; there is no useful treatment outside it because adults overwinter away from host plants.
Beyond the UK
The lily beetle is native to Eurasia but was introduced to North America (first recorded near Montreal in 1943 and near Boston in 1992) and has spread across many US states and Canadian provinces, moving westward through the sale and movement of potted lilies and bulbs. Gardeners in affected North American regions can use the same check-often, hand-pick approach.
✔ Grow lilies where you pass them daily. Two minutes of picking on a spring walk-past prevents most of the damage a lily beetle population can do.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- RHS — Lily beetle — Adults 8mm bright red with black head/legs; orange-red egg clusters on leaf undersides; larvae 6-8mm reddish-brown hidden under wet black frass; only lilies and fritillaries are hosts; check from early spring and remove by hand; adults overwinter away from hosts so no treatment out of season.
- Utah State University Extension — Lily Leaf Beetle — Lilioceris lilii is an invasive pest of lilies in North America, spread via shipped bulbs and plants.
- University of Connecticut Home & Garden Education Center — Lily Leaf Beetle — Introduced to North America (Montreal 1943, Cambridge MA 1992) and has spread across many US states and Canadian provinces; hand-picking and egg removal are core home controls.