Can anyone tell me what kind of mold this is on the inside of my cut bamboo?

http://i643.photobucket.com/albums/u.../file-1359.jpg

When I fell a pole to use to make these didgeridoo's I cut the pole into the lengths I will need for the didge's. I then roast them immediately over a very hot fire which turns the bamboo from green to a nice caramel color. Only occasionally I get this issue... Is the mold dangerous? Is there a treatment I can do to prevent it?

Thanks!