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Honeybee (Apis mellifera) brood pheromone is a blend of 10 fatty acid esters that stimulates worker pollen foraging, protein biosynthesis in the brood food-producing glands of nurse bees and queen oviposition. In separate experiments conducted in central Oregon, we tested the hypotheses that treatment of honeybee colonies with brood pheromone would stimulate increased bee foraging in hybrid carrot (Daucus carota) seed fields, and that in turn would result in increased seed yield. For both experiments, in each replicate, all honeybee colonies placed at one field were treated with brood pheromone, and those in a control field were not treated with brood pheromone. A total of 123,720 bee visits to flowers was recorded. For both sexes of flower, there were significantly more bee visits in fields in which colonies were treated with brood pheromone than in control fields (P< 0.05). There was also a significant preference for male flowers over female flowers (P< 0.05) by bees in the fields where colonies received brood pheromone when compared with control fields. Mean yields in fields pollinated by colonies treated with brood pheromone and those that were not treated with brood pheromone were 325.2 and 280.8 kg⋅ha-1, respectively. Mean percentage yield was significantly higher in fields where honeybee colonies received brood pheromone when compared with control fields that had colonies without brood pheromone (P< 0.01). Our results suggest that brood pheromone has the potential to increase honeybee foraging and seed yield in hybrid carrot seed crop. [ABSTRACT FROM AUTHOR]