logs that you collect from outside needs to be cleaned and bleached. You can also sterilized them in a slow oven (120 degrees to 150 degrees) for two to three hours. Wooden limbs can be sealed with polyurethane varnish to prevent places for parasites.
You also want to look over the piece to ensure there are no sharp areas or possible snag areas. Natural items look better, but it's easier to use purchased items that you can clean easier.