Fall is a good time to destroy older and newly hatched slugs. Chemicals, organic baits or hand picking are all effective. Also, since slugs feed on and hide in plant material, make sure to do a through fall cleanup. One slug can lay up to 500 eggs in one season. Some hatch in the fall while others spend the winter in the soil. For this reason if you rake over the area where you saw slugs in the summer it will expose over wintering slugs and eggs, killing them.