It sounds like slugs...

Hostas are among their very favorites. If you go out at dusk and pick up the leaves & look underneath. You may see them having a feast.

There are several ways to treat them organically. One is to mix a wee bit of ammonia in a spray bottle. Then when you see the evil critters give 'em a free shower. One squirt will do...

Another is to set out beer traps. I prefer this method. I use 2 litre bottles cut in half. Then you remove the cap from the top. Invert it so that it is setting inside the bottom half. Pour a wee bit of stale beer in the bottom and then set this on its side near the plants that you see the infamous holes. Then the following morning, you just toss the trap & no yucky handling of slimy slugs!

email me if you would like a pic or 2 to demonstrate this. It is so much easier...

If you are not sure that it is slugs, then take a sample in a plastic bag to your nursery and they will certainly be able to direct you.

Good Luck & Happy Gardening!

Slug-go is an organic slug bait/killer that is very effective. Beer traps alone won't do the job. Sluggo is safe to broadcast around plants, even if you have curious pets.

I gave up on beer traps years ago. Escar-Go is my choice.

Here is a link that might be useful: Escar-Go