Are you sure its mold? The reason I ask is this: I've seen mold grow as you describe, usually on a plum that has a split pit and a little air channel up near the stem into the pit, which allows the mold spores to enter. But, I've also seen white or greenish scar tissue form that is kind of mold-looking, sort of generic strands of fuzzy growth, as the plant tries to fill the void with something. Regardless of the cause, if its very slight, I just usually trim that part off with a knife and still use the plum. Your mileage, of course, may vary, because some people are more sensitive to molds than others.

I doubt it would do much good indoors for such a short period of time. I used corn meal to combat dollar spot fungus in my lawn and it takes a month or more before anything happens. The idea seems to be that corn attracts trichoderma fungi and these are mycoparasitic (they kill [some] other fungi). Not really an ideal scenario for indoor seed starting. For this year you can try bottom watering if it is feasible for you. By keeping the top layer dryish after germination you may be able to reduce or eliminate the mold growth, but that's iffy. Something you can do is lose the peat. Maybe not this year as you probably already have your supplies, but in my experience anything with peat gets the white fuzzy mold as well as green algae like stuff on the mix surface. Not everyone seems to experience this, but some do. I have a fan on my seedlings so I don't think air circulation is the problem. Well, it might be given that it is inside air that is circulating. Nothing I can do about that. What I have been using for seed starting is 100% vermiculite. I like it as it is completely inorganic and doesn't seem to support the growth of anything other than the seedling.

Dicot has given one method. I have found you can usually avoid fungus growth by venting the pots regularly. Take the plastic off every day or two, turn over the plastic and put it back on. I have never tried putting holes in the plastic as a venting method. Al

Clean it weekly, and not enough to notice will ever build up with decent ventilation. This is what baffles me more than anything. Unless you're dealing with high-maintenance materials, it just isn't that har to keep a bathroom of any age clean. But so many people cite their bathrooms as being "dirty" as a reason for remodeling. I can get anything but rust stains out of white grout. Just CLEAN it if it's dirty, and don't expect a new bathroom to magically stay clean. (I've even read posts by people upset that they have mildew in their new shower--as if it's the tilee-setter's fault! CLEAN the danged thing. It isn't rocket science.)