Lily beetle survey
The red or scarlet lily beetle (Lilioceris lilii) has become the lily growers' nemesis. Both the adults and larvae can defoliate lilies (Lilium and Cardiocrinum) and fritillaries (Fritillaria).
Adults are 8mm long, bright red with a black head and legs.
Eggs are 1mm long and orange-red, found in groups on the underside of lily leaves.
Larvae have orange bodies with black heads but are normally covered with their own slimy black excrement. The fully grown larvae are 8-10mm long. The pupal stage is in the soil.
The beetle became established in Surrey in 1939 and it remained confined to south east England until the late 1980s. By the end of 2009 it has become widespread in England and Wales and is spreading in Scotland and Northern Ireland.
Adult lily beetles emerge from the soil from late March to May. They feed and lay eggs on the underside of leaves of host plants from late April until early September. The eggs hatch after approximately a week. Beetle larvae can be found feeding on the foliage between May and the end of September. After about two weeks, when the larvae are fully grown, they pupate in the soil. Two to three weeks later new adults emerge. Despite claims in some literature, this beetle has only one generation a year. The beetles overwinter as adults in sheltered places, often in the soil but not necessarily near lilies or fritillaries.
As part of RHS research, the susceptibility of six different lilies was assessed (one species and five hybrids). Results from the trial indicated that the species lily Lilium regale was less susceptible than the hybrids. The results from the trial have been published - see Salisbury A, Clark S J, Powell W, and Hardie, J. 2010. Susceptibility of six Lilium to damage by the lily beetle, Lilioceris lilii (Coleoptera; Chrysomelidae). Annals of Applied Biology 156: 103-110.
The lily beetle is not native to the UK; it has been accidentally imported into Britain on several occasions. It was first noticed at the end of the 19th century, with a handful of short-lived infestations reported from England and Wales. However, it was not until 1939 that an established colony was discovered in a private garden at Chobham, Surrey.
By the late 1950s the beetle had become widespread in Surrey and was also found in Berkshire. Later, an analysis of records held by the RHS Entomology section up to 1989, and the results of an appeal in 1990 in the RHS magazine The Garden for records of the beetle, indicated that the beetle's range had expanded into Hampshire, Middlesex, Wiltshire, Dorset, Hertfordshire and Oxfordshire. During the 1990s the beetle continued to be reported from new areas of England and Wales and by the end of 2007 this pest had been found in almost every English county. In 2002 the beetle was reported for the first time from Glasgow and Belfast. Continued reports to the RHS indicate that the beetle is now established and spreading in Scotland and Northern Ireland.