A method to promote flower visiting by honeybees Apis mellifera L. (Hymenoptera; Apidae) on eggplants was examined by conditioning honeybees to associate eggplant floral scents with sugar-water rewards. The fragrance components of eggplant floral scents were analyzed by coupling solid-phase micro-extraction techniques and gas chromatography-mass spectrometry. The main fragrance component of the whole flowers and pollen of eggplants was identified as geranylacetone. The effect of scents on foraging preferences was investigated by feeding honeybee colonies with sugar water including geranylacetone during the evening before the test day. Foraging honeybees from geranylacetone-conditioned colonies tended to visit feeding sites with geranylacetone scent more than feeding sites with linalool scent and only sugar water. Twelve geranylacetone-conditioned honeybee colonies were placed in eggplant greenhouses. Foraging honeybees from all 12 colonies started visiting eggplant flowers the following day. Unconditioned colonies fed only sugar water were tested as a control. In 5 of 12 unconditioned colonies, foraging honeybees started visiting eggplant flowers the following day. In the other 7 unconditioned colonies, foraging honeybees waited more than 2 days before starting to visit eggplant flowers. We conclude that conditioning honeybees to associate geranylacetone—the main fragrance component of eggplant floral scents—with sugar-water rewards promotes flower visiting.
