The Royal Horticultural Society (RHS) has joined forces with the National Biodiversity Network to encourage UK gardeners to help map some non-native pests that cause serious damage to popular garden plants. Plants and shrubs such as Hemerocallis (daylily), lily, rosemary and berberis are coming under increasing attack from insect enemies.
The RHS science department has submitted 4,000 entries of location records of four non-native pests that have been collected via the Royal Horticultural Society Advisory Service (predominantly from RHS members) and from the general public via on-line recording forms on the RHS website. The pests are Red Lily beetle, Rosemary beetle, Hemerocallis gall midge and Berberis sawfly. This information helps establish the distribution and spread of these garden foes since their arrival in Britain.
Andrew Salisbury, RHS Entomologist says:
“Information on these four invasive garden pests will improve advice provided to gardeners and enable an assessment of the threat that these non-natives pose in the garden and the wider environment. The input from visitors to the web-based surveys is invaluable if we are to learn where these pests are and how they are spreading. “
The NBN welcomes the addition of these RHS datasets. Our Chief Executive Jim Munford says:
“Presently the NBN Internet Gateway makes 31 million species records available to the public. The addition of RHS data on invasive species is very welcome. It adds considerably to our knowledge of important pest species such as the red lily beetle. I hope gardeners will use the NBN; perhaps in the context of wildlife gardening, but also they can add to our knowledge through the RHS.”
Map 1: Before the RHS data were added to the Gateway – Data submitted by
About the Lily Beetle
The red lily beetle ( Lilioceris lilii ) has become the lily growers’ nemesis; the adults and larvae can devour a lily plant in a matter of days. The red lily beetle is an 8mm (about 1/4in) long bright red beetle with a black head and legs. Eggs are found on the underside of leaves in linear groups of up to 15. They are 1mm (about 1/16in) in length and bright orange when first laid but darken as they mature. The larvae have dirty orange-red bodies with black heads; they are rather rotund with a humped appearance. The larvae normally cover themselves with their own slimy black excreta and could be mistaken for birds’ droppings. Fully grown larvae are 8-10mm (about 1/4in) in length. The pupal stage is in the soil.
The lily beetle is not a native species 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 RHS’s first entomologist, George Fox Wilson.
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 for records of the beetle in the RHS magazine The Garden in 1990, 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 in Scotland and Northern Ireland.
The lily beetle is native to Eurasia, although it is currently impossible to know exactly where. It is now found almost anywhere that lilies are grown, and has become established in North America where it is continuing to spread. More information
The increase in the distribution of lily beetle over the past two decades has been coupled with a rise in its frequency as an enquiry to the RHS Members’ Advisory Service. Before 1980 lily beetle enquiries made up less than 1 percent of all pest enquiries received, but during the past two decades the proportion of enquiries has increased to more than 3 percent.
Adults emerge from the soil from late March to May. They feed and lay their 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 two weeks, when the larvae are fully grown, they pupate in the soil. Two to three weeks later new adults emerge and complete the life cycle. 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.
Both adults and larvae damage lilies ( Lilium and Cardiocrinum spp.) and fritillaries ( Fritillaria spp.) primarily by defoliation, but in heavy infestations the flowers, seed capsules and stems will also be eaten. Although adult beetles have been found on other plant species, only lilies and fritillaries are true hosts, on which eggs are laid and the larvae develop.
The lily beetle has been observed on 57 hybrid Lilium , 30 Lilium species, one Cardiocrinum species and five Fritillaria species. The scientific literature indicates that not all lilies are equally susceptible, although there has been no attempt to quantify these differences. As part of the PhD a field trial assessing six different lilies (one species and five hybrids) was carried out to assess the lilies susceptibility. Results from the first three years of the trial indicated that the species lily was less susceptible than the hybrids. The trial is continuing for at least one additional year before the results will be prepared for publication.