Yes, had this problem in a major way last year and if this humidity keeps up another day or two I’ll be having it again this year. Good dry hay stacked nice and kept dry getting surface mold.
I discovered in hindsight if you let the mold just sit there it will fester and grow, if you manage it you stand a chance to beat it.
What I do is use a large shop broom and aggressively beat/brush the outside of the stack while a fan is running blowing all the spores completely out of the barn. After brushing I take a leaf blower and blast the stack blowing all the dust I can off. I keep brushing and blowing until no more white smoke comes out when I pat it. I had to do this every day for almost 3 weeks last year.
If I found a bale that just refused to stop smoking, I’d pull it out and get it away from the barn.
The more air circulation you can get the better. I also discovered that it helped to be fastidiously clean about the floor. Even though my hay was stacked on pallets, any fallen chaff would mold in under 24 hours and just add to the misery, so every single time I handled hay I would use my leaf blower to blow every last little speck of fallen hay out.
I did experiment with wetting and steaming hay because it was getting painful to throw the hay out (not so much a matter of money, though that is always painful too, but a question of being able to replace what I tossed, it was a rotten year for hay - as is this year - and good quality dry hay was scarce, I was lucky to have what I did so I wasn’t giving up without a fight).
Completely submerging the hay did make it safe to eat (I’m talking hay with only the faintest poof of white smoke, any significant smoke or actual visible mold was composted immediately, well away from the barn and horses). My horses are pigs and I don’t trust them to “eat around” anything compromised. I inspected every single flake with my nose and the pat test before feeding it. Fortunately I only have two easy keepers. :lol:
When I tried steaming the hay, I was amazed at the results. Certainly the dust issue was resolved, but the steam seemed to bring back the sweet fresh smell too. The horses relished the steamed hay and I was able to safely rescue the marginal stuff (again, I was quick to toss anything significantly dusty, etc).
I self care board without electricity, so a hay steamer is just right out for me. What I did is put a few flakes into a large deep plastic garden cart/tub I have, use my propane water heater to spray the hay with scalding hot water and then cover the tub with a plastic bag and let the steam do its steamy goodness for 10 minutes. The smell was so nice I found it tempting :lol:.
Good luck. Few things are more stressful and miserable than having gone through the work and expense of putting up good hay for the year only to watch it mold away before your eyes. :no:
Hang in there, every day you stay tough and beat this nasty mold back is a day closer to better dryer weather.
So, we ended up tossing out only about 4 bales, and left the rest to feed. Hay is in short supply right now; if I get a dusty one, I’ll soak it before feeding.