Fungi dust on wall

[strain]

About a year ago I noticed a small black patch on my wallpaper - this got bigger as time has gone on. iIt was not damp but looked like black speck. I have now stripped the old wallpaper off and found the wall dry, however it has a dry dust like substance on it which I am unsure how to treat before the new paper os pasted on the wall - any ideas??

[obione]

hi not sure what this is but had something similar myself try wiping the area with neat bleach it appears to kill the problem off or it did in my case. also was told to be careful and not breathe in the dust cause if it is some sort of spores they are not good for the lungs.

[stevie-p]

Could be condensation,or damp,both can leave unsighly marks,but i would use bleach too,and maybe think about using a sealer on the plaster.

[strain]

Thanks - Going to seal the wall as suggested. Last night I continued to strip off the backing paper in prep for this and found the chalk like dust under that, however it only came through the paper at one place.