Sometimes honeybees are more attracted to dandelions or other blooming flowers than they are to your crop, and pollination suffers.
Honeybees will only actively work blossoms with a minimum of 7 Brix sugar content in the nectar (unless they are foraging for pollen), otherwise they expend more energy than they gain.
When you have a healthy crop where the blossom nectar Brix is higher than competing flowers, bees will work the crop first. High Brix nectar is the solution to poor pollination and limited honeybee activity.