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

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 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.

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).

Submissions to our organism surveys are stored permanently in an anonymised form in order to monitor the spread of the organism.  We may contact you within 2 months of your submission in order to verify your sighting but your personal data will not be permanently stored in connection with your submission and will be deleted after 1 year. We publish and share only non-identifiable data from survey submissions (such as a six figure grid reference) with third parties and the public for the purposes of scientific research and advancing understanding among gardeners.

A map of reports is given in the gallery below.

Thank you to everyone who has submitted records – read a blog about the surveys

Gardeners should look out for;

• Adult beetles which are 8mm 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 which reach 6-8mm 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 and so there is no suitable treatment outside of the growing season.

Check lilies and fritilaries frequently from early spring onwards so action can be taken before a damaging population has developed. When choosing management options you can minimise harm to non-target animals by starting with the methods in the non-pesticide control section and avoiding pesticides. Within pesticides the shorter persistence products (that are usually certified for organic growing) are likely to be less damaging to non-target wildlife than those with longer persistence and/or systemic action. Pesticide treatments are likely to kill natural enemies and are only likely to be successful if the entire plant can be reached.

Non-pesticide

• Where possible tolerate populations of plant feeding beetles
• Remove beetles by hand where practical
• 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
• The lily 'Defender Pink' is advertised as lily beetle tolerant
• One product is sold as a repellent against lily beetle, Grazers G4

Pesticides

• Organic contact insecticides containing natural pyrethrins (e.g. Bug Clear Ultra 2, Neudorff Bug Free Bug and Larvae Killer). These have a largely physical mode of action. These pesticides although broad spectrum have a very short persistence and so may require reapplication to keep beetle numbers in check
• More persistent contact-action insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Resolva Bug Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer, Provanto Sprayday Greenfly Killer) and cypermethrin (e.g. Py Bug Killer). These products have long lasting action against insects including those that are beneficial
• A broad spectrum systemic insecticide (which is absorbed and transported through plant tissues and has contact action) containing the active ingredient Flupyradifurone (Provanto Smart Bug Killer) is available for use on ornamentals and selected edibles. Systemic pesticides are widely considered to be the most environmentally damaging, remain active for a long time and will kill beneficial invertebrates

Inclusion of a pesticide product does not indicate a recommendation or endorsement by RHS Gardening Advice. It is a list of products currently available to the home gardener.

Download

Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)

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, the adult beetles will also produce aggregation pheromones drawing 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 a year and these late summer adults will not mate and lay eggs until the following year.