Hi bittup,
In addition of kapscool answer, please take care to give a specific internal name to the folders before generating the package to export your navtree, because otherwise automatic generated internal names of folders on DEV instance (such as Folder2142) won't match the QA instance folders names including the whole hierarchy (when they exist in destination instance). And it could be a mess for finding out where the folders have been put .
Regards
J-Serge