Best thing. Make sure it is clean before you roll it up for the winter. The mold is actually on the dust / dirt on the awning. And unless you have it under a cover. It's gonna get wet and mold.
I clean mine by in rolling it, spraying Clorox II, or Awsome on it, and then roll it back up, let it sit 20 min or so, unroll it and wash it.
BTW. You CAN if it is a manual awning unhook the supports from the side of the RV, let them slide under it, and the awning will then be against the side of the RV. You can clean it much better like that. but do be sure to rinse the Clorox, or awesome off before you let it touch the RV. It will take the wax off.