My Baton Rouge, LA based family members and their extended friend network make homemade andouille sausage and other various Cajun/creole sausages. Pecan is the only wood they use for the sausages that get smoked. They use pecan and other woods for smoking other meats but when it comes to sausage, particularly of the Cajun bent, it's exclusively pecan. It appears to be tradition down there, at least in parts of Louisiana.