How to recognise it
The adult beetles are bright red with a black head and legs, and are up to 8mm in length. Their sausage-shaped eggs are orange-red and usually laid in neat lines on the underside of leaves or on stems. They hatch into reddish-orange, hump-backed larvae which are covered in black slime (their own excrement).
Damage to the plant shows as dried white/brown patches on leaves (from the young larvae) or leaves and stems being entirely eaten away (by older larvae and adults).
From March the adults start to emerge and feed on plants. Each female lays 200-300 eggs throughout late spring and summer on stems and the underside of leaves. They hatch in around 10 days and the larvae feed for about a month. They then pupate in the soil within silken cocoons for two to three weeks before emerging as adults. In early autumn they move to overwinter in the soil or under debris (but not necessarily near the plants they feed on) until the following March. They continue to emerge until early June so it’s possible to have adults, eggs, larvae and pupae all present on and around the plant at the same time, however there is only one generation each year.
Why it’s a problem
Both the larvae and adults feed on leaves, stems and seed pods. They can completely strip the leaves from a stem.
Where you are likely to find it
They attack lilies (particularly Lilium candidum, the Madonna lily), fritillaries, nomocharis, cardiocrinum and Solomon’s Seal (polygonatum).
How to deter it
If you grow lilies and live in an area where the lily beetle is present then it’s difficult to avoid it. The best strategy is to be vigilant and deal with any beetles as soon as you spot them.
How to get rid of it
Manually remove and destroy any adults, eggs or larvae which you find on the plants. Keep an eye out from April onwards.
A contact insecticide (such as pyrethrum, deltamethrin, thiacloprid, imidacloprid or acetamiprid) can be used in the spring (as soon as you spot the pest) and repeated later if necessary.
Is it good for anything?!
They are remarkably attractive for such troublesome pests, but other than their pretty appearance they bring no benefits for gardeners.