The two most common reasons for holes in hosta leaves early in the season are slug damage and hail damage. Slugs will leave a silvery slime trail and can be controlled by handpicking at night when they are active, traps or baits (read and follow the label instructions carefully). Hail damage (or other physical damage such as that caused by trampling) may occur much earlier in the season and only become apparent when the leaves have fully unfurled and begun to grow.