Hello XXXXXX XXXXXX,
Welcome to Just Answer.
Sorry to hear about your problem.
I wouldn't worry about it. Wood contains moisture and if stored in a dark area, it will grow mildew on it, which is what you are seeing. As long it is in a sunny area now and has the chance to dry out, the mildew will eventually disappear. You can speed up the process by spraying a mildew cleaner or a little bit of bleach. Let sit for a few minutes and then wash thoroughly with water. Do not use these products if they may effect the horses though, and just let time take care of it.
If you need further help or clarification on this answer, please do not hesitate to reply to this post.
Thanks for asking your question at Just Answer.
Best of Luck, Brian
Please leave feedback at your convenience.
Mold and mildew have many similar characteristics, but they are different types of fungi, and are often different in color and texture. Mold and mildew are often mentioned together as they can both grow in many of the same moist and warm locations. However, mildew is often found more often than mold in showers, paper and fabrics and mold is usually found more often than mildew in foods. They can sometimes be difficult to tell apart as they both spread out from spores. Mold is often black, green, red or blue in color while mildew is usually gray or white.
Architect
Licensed Architect- 12 years, L.E.E.D. AP, Former Remodeling Contractor- 10 years