Bioassays for measuring ovipositional and larval preferences of leafrollers (Lepidoptera: Tortricidae) for different cultivars of apple

Abstract

Bioassays are described for measuring the ovipositional and larval preferences of three leafroller species, Planotortrix octo, Epiphyas postvittana, and Ctenopseustis obliquana, for different apple (Malus domestica) cultivars. In four-cultivar choice tests, mated female moths were offered terminal shoots in a large screen cage; first instar larvae selected terminal leaves in a smaller test arena. There were high levels of oviposition and settlement on all cultivars which agreed with field evidence of their susceptibility. However, there was overall higher oviposition of the three leafroller species (combined) on ‘Royal Gala’ compared to ‘Jonafree’, and for E. postvittana, higher oviposition on ‘Liberty’ than ‘Jonafree’. These cultivar preferences were also expressed in the responses of the first instar larvae of the respective species. The preference of E. postvittana larvae for ‘Liberty’ and ‘Royal Gala’ rather than ‘Fiesta’, and the preference of P. octo larvae for ‘Liberty’ rather than ‘Jonafree’, were not matched by adult oviposition behaviour of the species. C. obliquana showed no significant cultivar preferences but the acceptance ranking of the cultivars was the same in both the oviposition and larval tests. The bioassays are considered suitable for testing of leafroller oviposition and larval preferences using a wider genetic pool of apple cultivars in parallel with measurements of leafroller colonisation in the field. © 1998 Taylor & Francis Group, LLC.