Jim! This one's for you.
We all do it. We can talk all day to friends, colleagues and family without uttering a singled 'um' or 'erm'. But sit in front of a microphone to record a podcast and they pour out between every sentence.
So how do professional broadcasters and newsreaders speak without making these unwanted noises? Practice, practice, practice - a heavy dollop of self discipline.
Sure, we can edit our podcasts to remove these noises; but it can get boring after a while and it is time consuming - so far as I know - there is not an app for that (yet).
The best way to solve this is to train yourself not to make those noises at all.