By the time you see the beetle it is too late, the beetle doesn't do any damage its the lavae that causes the problem. You are just wasteing your money treating the beetle it has already laid the eggs.

From memory you need to treat about 4 weeks before you see the beetle to kill the lavae before it turns to adult stage.

From memory use baycor or baythroid can't remember exactly which one but can do some research and find out if really want.