The Complete Article is here: http://www.scientificamerican.com/podcast/episode.cfm?id=to-bee-or-not-to-bee-09-08-21
with the important except pasted below...
Berenbaum: Honeybees, everybody thinks eats honey and pollen, but in reality they feed their grub something called bee bread, which is a mixture of honey and pollen packed into cells, and it cures or ages. And the suspicion is that maybe some of these symbiotic microbes are contributing to the sort of processing of bee bread.
So one of the findings from this yet unpublished work that was discussed in Florida at the meeting that Reed attended, Apiary Inspectors of America, was a high-fructose corn syrup
which is the preferred diet for overwintering bees because it's much cheaper than feeding them honey or sugar; apparently it wipes out these potentially symbiotic microbes.
One thing that Reed 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].