Impact, host range and chemical ecology of the lily beetle, Lilioceris lilii

Abstract

The lily beetle (Lilioceris lilii, Coleoptera: Chrysomelidae) has a univoltine life cycle and a limited host range (Lilium, Fritillaria and Cardiocrinum). A survey of 237 professional growers indicates that L. lilii is a problem for many in the UK lily industry. A three-year field trial using six different Lilium indicated that the species Lilium regale is more resistant to L. lilii than the hybrids L. ‘Tiber’, L. ‘Brindisi’, L. ‘Conca d’Or’, L. ‘Eliganzer’ and L. ‘Golden Joy’. Phenology observations between the trial and an established population of the beetle have provided base-line data to which further observations can be compared. Future host susceptibility trials should use a standard lily such as L. regale against which others can be compared. Behavioural bioassays using a linear-track olfactometer demonstrated that the responses of L. lilii to hosts and conspecifics are at least in part odour-mediated. Significantly more diapaused females moved into airstreams containing the odour of intact hosts over clean air, to that of hosts and beetles combined over that of undamaged or manually-damaged plants, and into airstreams from intact plants over larval-infested plants. Pre-diapause males moved into the airstreams of intact hosts in preference to L. lilii-infested plants. Using air entrainment, gas chromatography (GC) and coupled gas chromatography-mass spectrometry (GC-MS), headspace volatiles from beetleinfested host plants have been collected and identified. From these compounds, methyl salicylate, nonanal, cis-jasmone, linalool, 6-methyl-5-hepten-2-one and β-pinene elicited electrophysiological responses from L. lilii using electroantennography (EAG) and coupled GC-EAG. Bioassays indicate that diapaused female beetles move into the airstream of clean air in preference to cis-jasmone. Investigations from all areas of the project have progressed our understanding of the ecology of L. lilii but further studies are needed before more effective control strategies can be developed.