Thanks so much, cat_ky! That was great advice! The crawl space has a big opening with a screen to let in air and be opened for any repairs, but I found other openings that need to be sealed. But I'm afraid if I seal them, the mice left will come up into the house. I am sealing all openings I found inside the house and under the sinks and oven, but don't know if trap or poison is a good idea to put in crawl space to get rid of the ones already nesting. Is there any danger to doing that? Thanks.

Hydraulic cement is a good idea for sealing mouse-size (dime or larger) holes in masonry. In most cases, ordinary vinyl patching cement will work too.

I've sealed up mouse entry holes in wood using coarse steel wool and various adhesive-type substances, from silicone caulking to wood dough. The steel wool seems to be what actually deters their chewing. The sticky stuff keeps them from pushing it out and prevents rust.

I'm not a big fan of poison for eliminating mice and rats. IMO it poses too much risk to pets and other desirable animals.

So I prefer traps. But you have to check them daily. I like Jawz. Bait with cheap generic peanut butter.

The good thing about traps is that since you check them regularly, you find the corpses and can dispose of them before they start to stink.Cats are a traditional solution and can be pretty effective for mice control, though not so great for rats. Some cats are more aggressive than others. Younger is better. They appreciate the animated toys more. :) Old cats get complacent.

I've read that female cats are better mousers than males (neutered or not), but I haven't noticed a lot of difference.

Cats would be more useful in the house. You probably don't want to lock your cats up in your crawl space. I'm quite sure your cats don't want to be locked up there.

If you must use poison, put it in wooden boxes about 4" x 4" x 12"
(dimensions aren't critical) with a dime- to quarter-size hole in one
end and a removable top that can be secured. Screw down an old cat food can or jar lid in the end away from the hole, and put your poison in that.

This keeps larger critters you presumably don't want to
hurt, such as cats and dogs, from getting to the poison (though they can probably still be sickened or die from catching and eating poisoned mice and rats). Place
the boxes along walls because mice tend to stick close to walls when
they scurry.

As I said above, I don't like poisons, but once when I had a major rat
problem that I wasn't getting under control with traps, I had good
results from Just One Bite bars. But keep in mind that poisoned mice can crawl into inaccessible places to die. Yes, they do smell.

You can buy flexible metal wire mesh like this https://www.homedepot.com/p/Acorn-International-1-4-in-x-24-in-x-50-ft-23-Gauge-Hardware-Cloth-HC42450/300661419 in sheets at HD and Lowes, and it works well to seal out rodents but keep the ventilation in a crawl space. You will need to use large staples or short wood strips to hold the edges down completely. You can also make a frame out of wood strips, staple on the mesh, and then screw on the frame/cover to make it removable.

Mice can easily get through openings as small as about a nickel or quarter, and they find small spaces around drain pipes and other holes that seem to be really small. If its hard to put mesh over a small opening, you can roll or fold up the wire mesh and just stuff it in a hole to stop them. You can also use canned spray foam around pipes to get a good air seal, but use the metal mesh first because mice can gnaw through the foam.

Spray foam for windows and doors is easier to work with because it has a lower expansion rate than the common "Great Stuff Gaps and Cracks." However, all these foams are messy and very sticky on your hands, so use latex or rubber gloves to keep it off your hands. Dried foam is much harder to remove than paint, but you can usually get it off if you wipe it immediately.

Bruce

I dont know about diseases, but, they will stink for a week or two. The granuals deter them from staying in the crawl space. They are used in the rented storage buildings all the time.

I can't recommend poison: I had a friend who used poison to deal with a rodent problem. Several of them crawled into the walls and died. The smell inside continued for months.

Also remember that mice can squeeze through very narrow spaces, like the cracks under doors, as well as wherever there are plumbing penetrations, like behind your dishwasher, etc. So don't expect to eliminate them 100% through sealing up the access points you see. Plan to use traps inside for a while.

Great suggestions, all! Thank you very much for taking the time to reply and give valuable information.