When mowing you see them, learn where they are, or scalp them. And if they are less than the cutting height, they are not an issue. However, the aerator is going 3" under the surface. Where you can't see them. Even if they have a visible portion above ground, there is no guarantee where they go after that. Or how long they stay close to the surface. Or if they dip low and then go near the surface again. How do you handle the roots? Or are they even an issue?