There is ever very little formal research done when it comes to the do's and don'ts of reptile keeping. What we teach as successful husbandry practices today is because of decades of trial and error by people like Bob Clark and Dave/Tracy Barker that were in on the ground floor of keeping pythons.
I know that Pine, Cedar and any aromatic ever green sap is a natural irritation to snakes skin. We know this because Woodpeckers and other wood boring birds have been proven that they use it to ward off snakes in the wild. The fact that its dried doesn't mean the sap is gone it just means that its dry. It would stand to reason that if brief exposure to this sap is enough to ward off reptiles then a prolonged exposure to even the dried could possibly have an adverse effect on the animals.
Is this proven over many different study's? No not even close..They way I see it better safe than sorry. You might could keep 200 animals on pine for two years and never have a problem. And then you might only lose one animal. To me its just not worth the risk .
