Your a little further SW of here, We have had some cold novembers and snow here over the 61+ yrs i have been around so i have different expectations.................lol
Yup, One of the warnings on the bag about inhaling it, Its also used in grain silos, I usually wear a mask in an area that's enclosed, But i also have the applicator bottle with the various tips, Good stuff and very effective.
Need to sweeten those little buggers up before dehydrating them, You can sprinkle a little food grade diatomaceous earth as well and that will take care of those ants, spiders and a whole host of others including fleas and bed bugs.
There the best, Don't waste your money on anything else, You will see an uptick in activity once you place them for a day or two, Then they will be gone.
Different reasons for frozen ground up this way, A third of the trail system here for riding purposes requires riding over some wetland areas so frozen is a requirement for access.