Bill,
In simple ASPIRIN statements:

Drone brood trapping is a part of the new IPM theory.  Because the gestation
time for a drone is 24 days, 3 days longer than worker brood gestation, it
would appear that the female mite prefers to lay her mite eggs with drone
larva rather than worker larva, hence providing more food for her mite
progeny as well as perhaps more mites per bee cell than a worker bee cell.
Hence, by entering one frame of drone size foundation into a brood nest and
removing it BEFORE the drones emerge would badly deplete the Varroa
population of a colony.

Is that "declared simply" enough?

George Imirie