Fig. 4.

Mean residence time of Trichogramma brassicae females on Brussels sprouts leaves treated with Accessory Reproductive Gland (ARG) homogenate of virgin females and indole or treated with indole alone (amount shown in ng). Test leaves were treated either with ARG extracts from virgin P. rapae females and indole or indole alone (dark grey bars) and tested against control leaves treated with ARG extracts from virgin Pieris rapae females or methanol only (light grey bars) a) 24 h or b) 72 h prior to the bioassay. Untreated leaf area, adjacent to a site on the same leaf that was treated with ARG homogenate and/or indole was simultaneously offered against leaf squares taken from ARG-homogenate or methanol-treated leaves in a two-choice contact bioassay in a Petri dish. Female wasps per bioassay combination, N = 50. Abbreviations: MeOH—methanol; ARG—accessory reproductive gland; ns—not significant; *P < 0.05; ***P < 0.001 (Wilcoxon matched pairs test)