I am rethinking feeding my bees sugar syrup and will do so only if I have no harvested honey on hand to give my bees. I won't use honey from other apiaries because I don't know the condition of their hives and feel confident giving them honey from my hives. Here is an excerpt from an entomologist regarding sugar syrup (I don't use corn syrup but use white granulated sugar when making sugar syrup).
One thing that Reed Johnson found that's in his dissertation, when you feed honeybees honey, they upregulate their cytochrome p450 monooxygenases, these enzymes that process among other things plant chemicals, when you give them sugar, it's nothing. So when you feed them on a sugar diet they are not turning on their chemical processing equipment, so this is something that nobody expected. I mean people aren't used to thinking of honeybees as broad generalists because they'll feed on hundreds of different flowers, but in a way they are dietary super specialists because they feed on this narrow range—they feed on pollen, honey and bee bread. And granted the components can come from all different places, but feeding on nectar or honey derived from nectars [is a] very different proposition from feeding on other types of plant tissue because plants load up their vulnerable tissues with chemicals, you know, natural pesticides, so that insects won't eat them, but they want insects to eat nectar; that's the whole point [of nectar].