My Bijou is molding in the jar.
You better go see a doctor about that! (Har!) Seriously, I find it interesting that this seems to be becoming an increasing issue in the modern era of recent blends. I wonder if it is a byproduct of decreased QC under the pressures of the FDA or changes made in the search for newer and ever-more-interesting blends?
Cigars--- I used to be a big cigar smoker and mold is not much of an issue there. First, they are usually under constant control in a humidity (and often temp) controlled environment, and second, any spot of mold (often it isn't even mold but just normal bloom) is just along the outer wrapper and easily wiped away. Tobacco being mainly a porous and loose fiber is much more susceptible to deeper contamination.
Is it harmful? I can't say how safe your mold is but as recently discussed, probably not the best thing to ignore unless you are sure. Even "good" mold like penicillin will have an effect on you (it cures diseases!) and bad molds might do anything from cause minor illness and flu symptoms to organ damage and beyond. Is a jar or tin of tobacco really worth all of that?
Heat will kill mold and sustained temps above 140° will kill most varieties, but that said, killing the mold still leaves behind any toxins produced as byproducts (waste) of their eating the tobacco and that is really what you have to watch.
If the mold is white or gray, and localized, it is your choice to try to remove the moldy parts and an inch around it in loose tobacco, maybe less if it is solid cake, then take the remaining tobacco, put in a fresh, clean container and bake for a while (a couple of hours?) at above 140° and take your chances. That might caramelize the tobacco and make it better anyway. Sterilize the old container.
If the mold is blue or green, throw that stuff away.
I've heard people say they never buy any C&D blends and to me that's a shame because they offer many good blends not found elsewhere. Looking over my inventory, I don't think I have anything to worry about. My current C&D inventory is (in bulk):
Long Cut Perique
Blending Latakia
Old Joe Krantz
Dark Chocolate
Billy Bud
Autumn Evening
Epiphany
Star of the East
and I don't plan on stopping buying from them, and I have seen absolutely no issues with any of those, whereas the only C&D tins I have right now where there might be a greater risk are:
Pirate Kake and Black Frigate
and no one seems to have any Frigate issues.
Why the mold?
The causes are few---
* Some sort of potential quality control / storage issue at C&D?
* Source tobaccos being brought in and used for certain blends are coming in contaminated due to improper ventilation during drying or the crop was subject to bad weather?
* Improper cleaning and processing of the tobacco during deveining leaving active mold in the bales?
* Mold is being promoted with one/some of the processing methods used to post-treat, condition or age certain tobaccos for a blend.
C&D will have to resolve this whatever the cause and find a way of changing things to bring this under control.
What can we do?
Mold is everywhere. In the air, in every breath in the form of spores, waiting for a trigger. All it needs is the right moisture content and temperature. In tins, you have little control over moisture, but in bulk, your moisture content should be close to 30% at most I believe to minimize risks, or measured differently, open a jar and put it in a sealed ziplock with a digital hygrometer for a couple of days. If it reads 70% RH or higher, you have an issue. Better I think would be in the 60% or lower.
The only other thing you can do is control temp. Warmer temps certainly make mold easier to grow, so, if you have any suspect tobaccos that worry you, keep 'em cool. Maybe even put them in a fridge. If you can drop the storage temp by 20°, you probably cut the chances for mold development in half.
One other possibility is to try sterilizing your tobacco with strong short-wave (tanning) UV light. That might kill active mold but might not kill all spores. And while retarding aging, eventually, bacteria inside the tobacco should reestablish itself again.
Good luck.