The Use of Olfactory and Visual Cues in Host Choice by the Capsid Bugs Lygus rugulipennis Poppius and Liocoris tripustulatus Fabricius

Lygus rugulipennis Poppius and Liocoris tripustulatus Fabricius (Heteroptera: Miridae) are pests of glasshouse cucumber and sweet pepper crops respectively. L. rugulipennis has a wide range of foodplants, but L. tripustulatus is specialised with very few food plants. We report behavioural assessments to investigate whether either species exhibits a preference for salad over wild hosts, and whether the role of olfaction and vision in response to cues from host plants can be distinguished. Olfactory responses to leaves were tested in choice chambers. L. rugulipennis was presented nettle (wild host) and a salad leaf of cucumber or sweet pepper, where the salad leaves had higher nitrogen content. L. tripustulatus was tested with nettle and sweet pepper of two different nitrogen contents. Female L. rugulipennis spent more time on the cucumber salad host, and chose it first most often, but males showed no preference. Neither sex discriminated between sweet pepper or nettle leaves, but males made more first contacts with sweet pepper. Neither sex of L. tripustulatus discriminated between sweet pepper and nettle leaves when the sweet pepper had higher nitrogen. When the plant species contained equivalent nitrogen both sexes spent more time on nettle. There was no difference in first choice made by either sex. When visual stimuli were available, and leaves had equivalent nitrogen, L. rugulipennis showed no preference and L. tripustulatus preferred nettle leaves. We conclude that the generalist L. rugulipennis has the ability to use remote olfactory cues for host choice whereas the specialist L. tripustulatus relies mainly on contact chemosensory and gustatory cues.