I'd say you can absolutely put the pieces in your tank. The pieces you find at the local rivers are the best. That's all I use, because the price is right!
In a humid climate, you'll need to spray the pieces with a pressure nozzle attached to a garden hose. Then, just leave them out in the sun for a couple of hours and they'll be tank ready. You'll need to pick up some good sized rocks too. Without the rocks, the wood will float. Eventually, you won't need the rocks, the wood will stay at the bottom.
Some fishkeepers say to use chemicals like vinegar or boiling, etc. to kill any bugs, but I've never done any of that and never had a problem. But, I live in Colorado and it's very dry here. Bugs couldn't survive the climate, let alone the noon sun in June.
Use your judgment on cleaning, but the piece will look good in the tank.