Chambers, I am absolutely not an expert. My first thought I'd that it may be FA. Is the stuff only on structure? Or on the bottom too? Are you sure it is a problem?

You could spot treat some with a copper product - see threads here on control of FA- and see if that kills it.

I'm my opinion, a little FA is not bad. Of course, there comes a point when it most certainly is a problem. Each of us has a different thresh hold for that I suspect.

Good luck with your stocking! Exciting times.

Are you in the path of the little storm heading up the east coast? Be careful if so.

CMM