I have 32 colonies of bees in my backyard. I also have brug blooms most of the year and have never seen any sign of brood disease from brugs. There are only two plants that I know of that cause brood disease. Those are summer Ti-Ti and, rarely, blueberries. There are times in winter when the only thing blooming are a few brugs and the bees swarm them for their pollen with no apparent ill effects. Two other plants that can cause problems are rhododendron and Confederate jasmine but these are usually in the form of poisonous honey. That almost never happens since there isn't enough bloom to allow for any surplus honey.
