Aaron Morris wrote:  However, Harbo has done some impressive experiments showing
how powerful an attractant is drone brood, so perhaps there would be a massive
immigration.


This sounds to me as if the drone brood emits a pheromone which attracts the Varroa mite.  If this pheromone could be isolated and mass produced it suggests two methods of attacking Varroa infestation:
1)   Placement of pheromone bait in locations within the hive to draw the mites away from the brood frames.
2)  Placement of the pheromone throughout the hive so as to totally confuse the mites in their quest for host brood.

Any ideas along this line folks?