I've found them everywhere - can't say specifically the grubs on the roots, but when I grew Geranium endressii in the ground I could hardly see any foliage because the adult weevils ate it so enthusiastically.

I dealt with black vine weevils...not sure if the same thing, but I'm sure they are related. They would attack my honeysuckles, primarily. I did the squash approach (each evening, out with a flashlight), but that would be tricky on hostas. Have you tried beneficial nematodes for the grubs? We can't buy pesticides in Ontario, so I have tried those for other kinds of grubs. Problem is, it's so hard to know if they are working or not. I've also seen suggestions for sticky substances on the base of plants to catch them....like tape, or even honey. Again, that would be tough for hostas. But every adult you catch will limit next year's grubs somewhat. Edit: I love your Cracker Crumbs! I've been looking for something to brighten up my shade garden. I'll have to go find one. :)

Are the plants indoors or out? In containers? If outside and in containers you can try the nematodes but timing needs to be just right. They need to be applied when the weevil larvae are active and getting ready to emerge, which is usually mid to late summer in my area. But you will have to address the adults as well. And that can be done without any chemicals and is probably more efficient without. Weevils are nocturnal so go out just before dark and spread sheets or open newspapers around the plant and shake it hard. If you can pick it up and shake, so much the better. They are very clumsy insects and can't fly so they just fall off. Pick them up and dispose of them in a bucket of soapy or ammonia water. You may have to repeat the process a couple of times, a week or two apart, but that should get them.

Yes. The grubs only affect the roots.