I have had a few sheets of low grade (bought from Global house) plywood stored in a downstairs roomfor the last three years.

A few of them are painted. I have been away for three months and in that time a spectacular growth of cream couloured fungus or mould has grown on the plywood.

what alerted this to me. was when I went to use the small backpack that I use for cycling was also covered in mould.

The deposit is a small 3mm-1/8 hemisphere that is cream coloured. It turns to powderwhen touched.

The painted plywood has had a proprietry anti mould treatment sprayed on with the base coat. the deposit is mainly on the edges of the plywood.

Does any one have a quick fix for this. I was thinking vinegar or lime ( where would I find lime)

I think you have already answered this yourself.

Just wipe it all down with a damp cloth let it dry and retreat it with an anti mould treatment spray or brush on type.

if its into the wood, its Done.

Otherwise, wire brush away any loose wood material, then spray solid material with 10% bleach solution in water and work it in. let dry in the sun and/or moving airstream. Fungus will be dead.