Lily beetle and its larvae feed on the leaves of lilies and fritillaries. The adult beetles are very occasionally found on other plants, but lilies and fritillaries are the only plants on which eggs are laid and the grubs develop. Plants can still produce a good display of flowers despite leaf damage, although heavy defoliation in early summer can result in undersized bulbs, which may not flower next year. Lily beetle has become widespread in Britain and Ireland since the early 1990s.

Lily beetle is a leaf beetle (family Chrysomelidae), with about 250 species of leaf beetle found in Britain. They all feed on plants, but most do not have a noticeable effect on garden plants. Leaf beetles range in size from 1 mm to 18 mm, and many are colourful. Many species are local (restricted range) or rare. More information on British leaf beetles can be found from UK Beetles.

There are other red beetles: the cardinal leaf beetles (Pyrochroa spp., family Pyrochroidae) and red soldier beetles (e.g. Rhagonycha fulva, family Cantharidae), that can be confused with the red lily beetle, these do not cause damage to lilies, giant lilies or fritillaries.

Seen the lily beetle? We would like to know.

As part of RHS research we would like to know where the lily beetle has been seen.

Please submit your records via our lily beetle survey (expected time to complete survey = two minutes).

A map of reports is given in the gallery below.

Thank you to everyone who has submitted records. Discover other sightings you can report to help our research.

Gardeners should look out for:

• Adult beetles which are 8 mm long and have bright red wing cases and thorax. The head and legs are black
• Clusters of orange-red, sausage-shaped eggs on the undersides of leaves
• Larvae reach 6-8 mm long and are rotund, reddish brown with black heads. They are usually completely hidden under their own wet black excrement (insect excrement is known as frass)
• Young larvae graze away the underside of leaves, resulting in white or brown dried-up patches. The older larvae eat entire leaves, starting at the tips and working back to the stem, they can also feed on petals, stem and seed pods 
• Adult beetles make rounded holes in the leaves and can also feed on petals and seed pods

Lilies and fritillaries can tolerate some damage from this insect. However, in some cases, plants can be stripped of all foliage, which can affect the health of the bulb. The adult beetles overwinter away from host plants.

• Where possible, tolerate populations of plant-feeding beetles
• The lily 'Defender Pink' is advertised as lily beetle tolerant
• Encourage wildlife in the garden, such as birds, frogs, wasps and predatory ground beetles who will eat the larvae and sometimes the adult beetles. There are three species of parasitoid wasp known to occur in Britain that feed only within the larvae of lily beetle (Lemophagus errabundus, Tetrastichus setifer and Mesochorus lilioceriphilus). Infected larvae do not survivie
• Remove beetles by hand where practical
• One product is sold as a repellent against lily beetle, Grazers G4

Red lily beetle overwinters as adult beetles in soil, leaf litter and other sheltered places. This could be anywhere, not necessarily in the vicinity of lilies and fritillaries. They can also fly and find new hosts in the spring. They find lilies and fritillaries at least in part by volatile chemicals given off by the leaves, and the adult beetles will also produce aggregation pheromones, which then draw more beetles to suitable host plants. Consequently, there is no advantage in attempting to treat the soil below lily plants. The beetles begin emerging on sunny days in late March and April, when they seek out the foliage of host plants.

Eggs are laid in small batches on the underside of leaves during April to mid-summer. The eggs hatch and the larvae feed on the foliage. When fully fed, the larvae go into the soil to pupate. The next generation of adult beetles emerges from mid-summer onwards. These beetles add to the feeding damage, but there is only one generation per year, and these late-summer adults will not mate and lay eggs until the following year.