Ok, I am definitely going to try the white vinegar idea to kill the mold. I thought to disinfect it to use bleach, but I thought that might be too harsh. The vinegar sounds like it won't eat my leather. I already use baking soda and vinegar to clean off my bits and it's great.
Maybe with the holiday I can get around to it this weekend!
Only thing is, everything needs to be washed (except the horse, did that last weekend!) so I will have to keep the moldy stuff for last.
And I'm definitely going to price the Murphy's Oil soap. Has anyone found if it's cheaper than saddle soap? I know the bottles are bigger, so is it a better value?