Effects of -Jasmone Treatment of Brassicas on Interactions With Aphids and Their Parasitoid .

There is a need to develop new ways of protecting plants against aphid attack. Here, we investigated the effect of a plant defence activator, -jasmone (CJ), in a range of cultivars of and . Plants were sprayed with -jasmone or blank formulation and then tested with peach potato aphids ( Sulzer) (Hemiptera: Aphididae) and their parasitoid (M'Intosh) (Hymenoptera: Braconidae). CJ treated plants had significantly lower aphid settlement than control plants in a settlement bioassay. Conversely, in a foraging bioassay, parasitoids spent a significantly longer time foraging on CJ treated plants. Our results reveal that CJ treatment makes plants less attractive to and less suitable for but more attractive to in a range of brassica cultivars. It is likely that these effects are due to changes in volatile emission indicating activation of defence and presence of conspecific competitors to aphids but presence of prey to parasitoids. Increases in volatile emission were found in CJ induced plants but varied with genotype. Among the synthetic volatile compounds that were induced in the headspace of CJ treated brassica cultivars, methyl isothiocyanate, methyl salicylate and -jasmone were most repellent to aphids. These results build on earlier studies in and show that tritrophic interactions are influenced by CJ in a wide range of brassica germplasm. The implication is that CJ is a promising treatment that could be used in brassica crops as part of an integrated pest management system.