I too think the bees are secondary, I think they are there to lick up the sap the plant is oozing after being damaged by something else. My guess is slugs or snails. Spray the area w red pepper and garlic, and then put out a saucer of beer overnight and see if there are slugs. If so, you can buy slug pellets, at lowes, they are not expensive ($10 but go a long ways, maybe every two months?) and just start treating for the slugs regularly for a couple of years until you get rid of them. you may be able to see slugs snails if you dig around the plant, they love mulch-dampness...
