Honeybee Pollinators Use Visual and Floral Scent Cues to Find Apple (Malus domestica) Flowers

Apple flowers of most varieties require pollinator-mediated cross-pollination. However, little is known about the cues used by pollinators to find the flowers. We used bioassays to investigate the importance of visual and olfactory cues for the attraction of honeybee pollinators to apple flowers. Chemical-analytical and electrophysiological approaches were used to determine floral scents and investigate antennal responses of honeybees to scents from flowering twigs. Bioassays showed that visual and olfactory cues were equally important for the attraction of honeybees to apple flowers. Floral scents were dominated by aromatic components, mainly benzyl alcohol, and the antennae of honeybees responded to a large number of components, among them to benzyl alcohol, linalool, and indole. Our study aims to better understand how this important fruit crop communicates with its main pollinators. This knowledge might be used to improve the attractiveness of apple flowers to pollinators to optimize fruit sets.