Winter and summer morph Drosophila suzukii differ in foraging behavior towards phagostimulant baits

Abstract: Control of Drosophila suzuki, an important global pest of soft and stone fruits, still
depends mostly on insecticide sprays. Bait sprays, consisting of a food lure laced with an
insecticide, can achieve control with a reduced insecticide dose. The key to their effectiveness
is how well the pest engages with the bait. We investigated how food lure composition
influenced feeding by summer and winter morphotype flies. We compared a sugar-based food
lure with a protein-based food lure and we tested the phagostimulatory effects of different
ingredients mixed with the sugar-based food lure. In a separate experiment, we compared a
sugar-based and a protein-based food lure, mixed with diminishing concentrations of spinosad to see if lure composition affected dose-response curves. Several additives affected the behavior of both winter- and summer morph flies, evidenced from lower feeding rates, but not always in a similar way for the morphotypes. The sugar-based baits induced mortality against summer morph flies at lower concentrations of spinosad than the protein-based baits, indicating that the summer morphs fed more from the sugar-based bait. For winter morph flies, the protein-based baits showed a trend towards a lower required insecticide dose (ED50) compared to sugar-based baits. Overall, we found substantial differences in feeding behavior between summer and winter morphs that deserve consideration for pest control.