Fig. 1.

Arrestment of Trichogramma brassicae wasps on treated Brussels sprouts leaves. Mean residence time (± SE) spent by the wasps on two simultaneously offered leaf squares in a Petri dish. Leaf squares were treated with the following: (i) accessory reproductive gland (ARG) homogenate from either virgin or mated butterfly (Pieris brassicae) females and tested versus leaves treated with solvent only (control), (ii) ARG homogenate from virgin butterflies and added benzyl cyanide (BC) (test) and tested versus leaves treated with solvent only (control), or (iii) with BC (test) and tested versus leaves treated with solvent only (control). (A and B) ARG 24 h or 72 h local. Untreated leaf area, adjacent to a site on the same leaf that was treated (A) 24 h or (B) 72 h previously with ARG homogenate, was offered to the parasitoid. (C) ARG 96 h systemic. Untreated leaf area, adjacent to a leaf treated 96 h before with ARG homogenate, was offered. (D) ARG and BC 72 h local. Untreated leaf area, adjacent to a site on the same leaf that was treated 72 h before with 100 ng or 1 ng BC in ARG homogenate of virgin P. brassicae. (E) BC 72 h local. Untreated leaf area, adjacent to a site on the same leaf that was treated 72 h before with 1 ng BC. (F) BC 24 h local. Untreated leaf area, adjacent to a site on the same leaf that was treated 24 h before with 20 μg BC. (G) Female Trichogramma wasp of approx. 0.5 mm on P. brassicae eggs that were deposited on Brussels sprouts (credits: N.E.F., www.bugsinthepicture.com). In each treatment, 50 wasps were tested. Asterisks indicate significant differences between test and control within the same treatment. *, P < 0.05, **, P < 0.01; n.s., not significant (Wilcoxon's matched pairs signed rank test).