I don't know where you're located but in southeast Florida my little soursop (in a pot) is looking ragged, but all of my anonna are looking good and they never do this time of year.

I definitely don't think your tree is having a problem with noise :-) The same goes for dust. Even sooty mold won't hurt a tree unless it's completely enveloped in it. Dust him off, keep on doing what you did last year.

IMO, you shouldn't go crazy with knee jerk unnecessary reparations like too much fertilizer, or water.

Oh, definitely keep workers with root killer at bay :-) All that I know of should put ON the stump not on the ground around it. I've used it in the past and bored a hole in the trunk and let it settle into the wood, nothing nearby died.

I think they should be especially careful if your soursop is relatively close to it and not let runoff from the stump leech onto the soil.

You said it was young and flowered how tall / old is it?

I really didn't know annonas get ragged around this time, although I believe I read something about them having a dormancy period during our dry season in one of the University of Florida's publications so that does make sense. What's your cultivation regime for yours gnappi?