Olfactometer screening of repellent essential oils against the pollen beetle (Meligethes spp.).

Essential oils can have an impact on pollen beetle (Meligethes spp.) host plant location behaviour. Lavender oil (Lavendula angustifolia) showed the highest repellency value in a previous laboratory study that compared five different essential oils (Mauchline et al., 2005). However, lavender oil is one of the most expensive essential oils – a fact that could seriously hamper on-farm implementation of this strategy. To find a cheaper essential oil with comparable efficacy to lavender oil, we compared the essential oils of Mentha arvensis, Eucalyptus globulus, Melaleuca alternifolia, Citrus sinensis, Citrus paradisi, Citrus limon, Juniperus mexicana, Abies sibirica, Illicium verum, Gaultheria procumbens, Cymbopogon flexuosus, Syzygium aromaticum, and Litsea cubeba using a Y-tube-olfactometer. Essential oils were diluted 1:10 in acetone and 40 μl was applied to a 3.1 cm-diameter filter paper. Filter papers were placed in the odour containers of the olfactometer together with a flower cluster of spring oilseed rape with 5 open flowers and 10-15 buds. The control treatment involved filter papers treated only with acetone. Hungry pollen beetles were released individually into the olfactometer. The beetles’ choices were recorded. Flowers and essential oils were changed between replicates. Six replicates with six beetles each were conducted. Highest repellency values were obtained for Mentha arvensis, Cymbopogon flexuosus, and Litsea cubeba