You should probably chuck the substrate and switch to paper towels or newspaper until you're sure all the mites are gone. I'm not sure how long you need to bake the wood..I threw in some cork bark into my oven for 10 mins at 400 degrees (and I kept an eye on it, I didn't want it to catch on fire) to steralize it (or so I hoped), but the 1.5 hour method is probably a lot better

At the time I had no idea how long or how hot the oven should be for that.
And the cork bark did smell like it was roasting in the oven..I don't recommend what I did.