Parasitoid abundance, aphid population mass and glucosinolate concentration from experimental ozone and diesel exhaust fumigation of Brassica napus

The experiment was conducted within field fumigation rings over two summer seasons (2018 and 2019). Brassica napus plants were separated into four groups of plants: 1) inoculated with 10 Brevicoryne brassicae aphids and netted until harvest, 2) inoculated with 50 B. brassicae aphids and netted until harvest, 3) inoculated with no aphids, and 4) inoculated with 10 B. brassicae aphids then exposed to free-living parasitoids. Aphid populations were collected from plants with pooters and weighed. Parasitoids were counted from sticky traps that were surrounded by aphid-infested and non-infested plants (groups 1-3). Parasitoids were taxonomically classified into two groups (Diaeretiella rapae and other parasitoids). Brassica napus plants were harvested (from groups 2 and 3) and analysed for glucosinolate concentrations. The number of D. rapae parasitoids that emerged from parasitised aphids were counted from sticky traps inside the nets surrounding plants that were previously exposed to free-living parasitoids.