Mildew? staining of SYP

I have a piece of 2x8 Southern Yellow Pine that forms the back slab of the bench I am building. I picked this board because it was straight, knot-free, and had consistent grain direction for planing. And the "dirt" on it would come off as I dimensioned it, right? WRONG!
I now have what looks like mildew--a grey staining, primarily in the early wood. Too late to replace it in my project (at least without a chain saw), and I'm wondering what to do now. I have a cutoff to experiment with. Resawing a small piece showed the grey stain to be throughout the wood, not just on the surface.
A dilute Clorox solution had no visible effect. Should I try it straight? Would wood bleach (oxalic acid?) do anything? My concerns are primarily to kill whatever this is if it is alive, so that I don't have spores possibly causing health problems, or something eating the wood. Only secondarily, I would like to get rid of the stain for appearances.
Planning to use either tung oil or BLO when bench is finished, if that makes any difference.
Thanks for any advice, or pointers to sources of information.
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Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

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http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/ch13.pdf http://www.fpl.fs.fed.us/documnts/fplgtr/impgtr01.pdf http://www.fpl.fs.fed.us/documnts/pdf1984/feist84a.pdf
Learn to love it. Once the wood's below 20% MC, the stuff won't grow.
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your comment is the crux of it:

That I can live with. It was very wet at the Borg, but has been sitting in a basement shop (which is bordered on two sides with finished rooms with conditioned air) for over a year, so is pretty dry now. Guess I will just seal it up and enjoy the stain.
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Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

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