A lot of people do boil wood before they use it, just in case it has insects or something in it.
And it is generally thought that wood from evergreens like pine or cedar are not as safe, though if they have been in water a long time, they would likely be ok. Think driftwood on the beach.
If you find fallen wood, it should be very, very dry, no sap or green left anywhere. Bark must be removed.