Unfortunately
European honey bees do not cause genetic dilution. Queens mate with multiple drones and therefore each of her offspring can have one of several fathers. Queens with African fathers will reach adulthood a few days before their European
halfsisters and will go around the hive and kill them in their
pupae. Since there is usually a good chance that in each hive is an area where Africanized bees are active, at least one young queen will have an Africanized father; Africanization tends to concentrate itself.
There was a plan to create a barrier of European bees in the Isthmus of Panama but the bees reached the location before the plan could be implemented. A bee barrier was created further north where a mountain range reduced the area which needed to be covered. The failure of this barrier prompted the reasearch which discovered the early hatching of African bees.