agreed! don't leave them alone. But, in my opinion, dog's rarely get "jealous" the way people do. They have more of a domination/submissive relationship. Your white lab being food aggressive, sounds like he is in the dominate role. Depending on the aggressiveness of the attack, he might just be asserting his dominance. If you are dominate over the white lab, let him know that the new puppy is welcome in the family.