bluesguy,
I have noticed that some of my fig twigs acted like that too.
The whole twig seems to be covered with little popcorn fluff.
The skin/bark splits and the white stuff bursts open.
It is NOT mold. It later turns an ugly brown.
Some roots may develop, but not from all.
I am not sure why, but I recall that it happened on certain
fig varieties (did not happen on others started under same
conditions), and it tends to be more pronounced if the
twig is on the more "green" and/or "very-wet" side.
[BTW, the top node part of the top twig, seems to be rotten
for a totally different reason.]