I've been buying packaged soil blends for a long time. I've never blamed the the new soil for pests, wanted to //////
but will admit when I used those little pop up peat moss starter plugs the gnats seemed to be born over night with those, and since then I use rapid rooters with nary a gnat in my garden.
could flood a bucket of new soil with water and see what floats, I did, saw nothing move ever, maybe eggs, proly not, I dunno. be sure nice to be able to lay the blame on the soil instead of my controls though...