I collect wood from various sources and i dont know whether it is treated or not.

When i get the wood i send it through the thicknesser then i store it in the rafters in my garage.

If i seal it with a stain then varnish it, will this protect it from bugs?

I dont stain and varnish the wood until i make something with it.

Anyone have ideas on how to protect the wood if it is not treated?