Fly colony

Drosophila suzukii flies used in bioassays were from a laboratory colony established in September 2012 at the University of Guelph from infested raspberries and blackberries collected at a commercial farm near Halton Hills, ON, Canada (43 N 34′ 43; 79 W 57′ 38″). Flies were kept in Plexiglas^® cages (26 × 26 × 26 cm), with mesh backings and sleeves for access, at 22–23 ^oC, 20–30% RH and 16:8 h L:D. Flies were provided with moist cotton batting and fed and reared on diet prepared by combining: water (4 L), agar (45 g), cornmeal (125 g), white sugar (200 g) and nutritional yeast (70 g) with propionic acid (17.7 mL) and methyl paraben (3.3 g) dissolved in 95% ethanol (33.3 mL). The mixture was boiled and then cooled before pouring into Petri dishes (9 mm diameter). Flies that were 5–8 d old were used for experiments. Flies were separated by sex and held without food for 20 h and without water for the final 2 h before the start of the experiments.