Mine molds no matter where I keep it... and we have a near-constant south wind at our house and my tack room door faces south. It's a roll up door, and I leave it rolled up in the summer... hasn't helped. I do have my tack room door to my trailer standing wide open, right now, just in case the flood from wild water hose that sprayed it down at camp a couple of weeks ago wasn't fully dried. SURELY it is, but since we're in a hot, dry, windy weather pattern, I figured I better let it air out.
I went with the apple cider vinegar in a spray bottle treatment last month when all my tack was furry. Sprayed, let the saddles sit in the sun for an hour, then cleaned with Lexol cleaner and conditioner.
Two weeks later, it was back, but not as bad.
It's aggravating, honestly and for some reason when I grab my saddle and someone sees mold on it, I always feel a little ashamed of myself, like I'm a bad horse mom or something. IDK.
"We are here to laugh at the odds and live our lives so well that death will tremble to take us."