When an Emergence Hole opens up, toss a grenade into it. This will automatically close the hole, and therefore keep the locusts from coming out.

The Hammer Of Dawn can easily destroy Emergence Holes. You must activate it by targeting an enemy first, and then aim it toward the Emergence Hole.

Fire a Torque Bow arrow into an Emergence Hole. This is somewhat challenging to do, due to the straight line of fire given by the bow. However, if you are close enough to fire while the line of fire is arced, it is possible to make it into the hole. A Torque Arrow stuck in the top of the hole will close it as well.

When there is an Emergence Hole, take out your Lancer, go over the hole, and hold B. When you do this, every enemy that comes out of the hole will get chain-sawed.