: Anyone have any good ideas on removing mildew stains from okume plywood?

If it's damp it probably goes deep. Clean it off as best you can with brush and dry it out to see how much damage. The stains may come out if it's just on the surface. However, when dried out check to see if the laminations are coming apart.
If it's dry it could be just on the surface and sanded off.

If it's stained deep then you are probably stuck with it. Is it small enough area to cut around and still get your material??

Rehd