This is a prime example of why you shouldn’t automatically spray a pesticide when you see chewed leaves. Because while there’s no denying that these leaves have been chewed, in this case, the remedy calls for a repellent, not an insecticide.
The hosta has provided a tasty snack for the resident groundhog (or woodchuck, depending on your regional preference–it’s still the same animal) family. These creatures are one of the most notoriously difficult garden pests. They tunnel, they climb and they have voracious appetites for greenery. And once a woodchuck has established a liking for your property, he will return year after year to mate and raise a family, ensuring repeated destruction.
The only proven method of control is fencing that not only extends four feet in height, but also goes at least a foot underground–and this proves impractical for most folks. Some call in a licensed wildlife person to relocate the animal.
In some states, it is legal to shoot them–it is not legal to do so in my state (much to the chagrin of some gardeners, I know.) I have gotten extremely lucky by planting herbs around the perimeter of the vegetable garden and only putting in peppers and tomatoes. He (or she) has sampled a pepper, found it not to his liking and has left the rest of the garden in peace for two years in a row. I can’t promise this approach will work for everyone.
Repellents to try would be the same ones that would work for deer and rabbits (but do not try them on edibles unless the label specifically says that they are approved for use on edibles!) and would be those that contain hot pepper, perhaps mixed with rotten egg.