Slugs are the primary pests on Hostas. They like the cool, dark habitat under the Hostas and then they come out at night to eat holes in the leaves. The safest product for slugs is diatomaceous earth, an abrasive powder that is too sharp for their tender bodies. Sprinkle it on the ground around your hostas and the damage will end immediately. Be careful not to inhale--or let your pets inhale--the diatomaceous earth.