I have alluded to this issue before, but I'm now at the point where I've tried a bunch of different things and nothing is working consistently, so I thought I'd toss it to the crowd for ideas.
I constantly have trouble with mold of various species growing in between my inner and outer covers. I seem to have less mold problems with migratory covers, since there is no space the bees don't have easy access to, but it happens occasionally with them too. The mold is usually white or green, occasionally black, but only if I let the situation progress too far without a cleaning. I have tried more ventilation and I've tried minimal ventilation. Obviously I clean the tops with vinegar, or if it's really bad, I bleach the cover and repaint it, but it just comes right back after a month or two. Is there anything else I can be doing to deter mold growth?