There is white mold and I have seen it grow on cigars. Like Fred said, If it is fuzzy it is mold.
However, with that being said; Samuel Gawith flake tobaccos are famous for getting the white streaks running down the grain of the flakes. This is normal and shows up more and more the longer that they tobacco ages. I have quite a bit of aged SG flakes and they all have it on them. It is integrated within the tobacco. I have noticed this on a lot of flakes from all different manufacturers, but it seems more predominate on SG. I am not sure why this happens more with SG flakes than with other manufacturers flakes.
You can use a strong magnifying glass or a jewelers glass and look at the white marks. If there is structure like webbing to it, it is mold. If it looks like crystals it is sugar, ploom, or whatever the heck it is that happens to well aged flakes and it is safe to smoke.
You can always err on the side of caution and go by the adage, "When in doubt, throw it out". But I suggest that you learn the difference between mold and sugar crystals (if that is what it really is) because if you throw out everything that you are unsure of, you could be missing out on some truly tasty, aged tobacco.
"When the Government Fears the People, There is Liberty;
When the People Fear the Government, There is Tyranny." - Thomas Jefferson
