The majority wipes off easily. Plans are for a light wipe-down with bleach and then to poly it.

Comments anyone?

Sounds good to me - bleach should take care of it, but anything water-
based won't be very good for your MDF. The bleach will kill the
fungi, but the MDF will absorb the water in the bleach. If this is
just your scrap box, I'd seriously recommend taking the whole box out
of your shop and tossing it in a dumpster, while breathing as little
of the dust/spores as possible. I work with a variety of fungi/molds
at work right now, and some can be pretty unhealthy. Your MDF mold
might not be too dangerous, but many fungal spores are allergens or
irritants even if they're not pathogenic, so I'd err on the side of
caution. I might even spray it with bleach and then throw it away.
If you really need to keep these particular cutoffs, you could try
bleach or alcohol, but setting them out in direct sunlight for a whole
day should do the trick too, then a good coat of poly/shellac/etc.
Any chance you could get a dehumidifier or better ventilation in your
gar-shop for the rest of the summer?
Good luck and stay safe,
Andy