The easiest way is to create a visibility sequence and just set those sections to never appear.
If you want one that's already made, use the one from PM's Jungle Japes level.
Here's a
linkOpen up your stage, go to the original background stage section (most likely called StgJungle00), right click (on ModelData), import, Visibility Sequence.
Then just choose the file I've uploaded for you. Should do the trick, but just so you know, I haven't tested this with other stages before