Since the behaviour is instinct- it will be hard to correct. Our shetland sheepdog herded the other dogs for 15 years. The other dogs just got to the point of ignoring her. She only stopped when she got to old to herd any more. My youngest GP likes to herd Bella, he is constantly attached to her ear or her scruff, guiding her around. She is silly, thats her baby and she puts up with it. He doesnt even try it with the rest of the crew, they would put him in his place before he could think about what he is doing. Since the one is a herding dog and the other is a hunting dog, this could be interesting. Maybe let them out seperatley until the Beagle gets older or just wear the herder out with exercise before the 2 are allowed to play. I would think though that since the beagle is so young- if the behaviour is not stopped, it will become a habit with both of them and will continue for the rest of thier lives.