Turns out that's not true.
Scientific testing seems to confirm what we've always suspected, but been hesitant to admit: there's no such thing as plume, only mold--which can be dangerous, but certainly not always--or just common bacterial plant growth. And now there's science to prove it.
The good folks over at Friends of Habanos put out a reward for anyone who can provide a cigar with plume that turns out to be anything but mold or bacteria. People responded. They sent the cigars to Australia Biotech Laboratories for testing. And they all came up with mold or bacteria.
Then there was a second round of testing. Same thing.
Don't believe it? See for yourself here. (While you're there, why not join the forum? It's a good one.)
So, okay, there's no Tooth Fairy. No big deal. The moral of the story is, mold is everywhere, so is bacteria, and normally our immune systems are equipped to deal with it. Wipe it off and get on with your life (unless it's green or on the foot of the cigar, which means it's inside the cigar, which may mean you're taking a risk of getting sick. Or at the very least, smoking a smelly, moldy, dank, far from optimum cigar.)
Hey, at least now we know the truth!