buildup or moss/mildew problem

[VickiC]

Hi,
I have either a buildup or moss problem on the surface of my PrimeAgra medium. It's very hard for me to tell which. I know this problem has been addressed in the past because I just read the thread last night, but I have looked for it tonight since I realized I have the same problem and cannot locate it. I do remember that Ray explained what the situation was all about and also gave advice to the member who posted the thread, as did some of you.

Since I started growing orchids less than a yr. ago, I have watered them using our home filtering system. A few months back I noticed the same problem that I have now, but less severe.....only a very light dusting of white "powder" on top of the medium. I thought this may be a fertilizer buildup (I use Dyna-Gro liquid--7-9-5) or else some chemicals may have been getting through our water filtering system. Whatever the case, I switched to distilled water, but continued my weakly-weekly fertilizer regime. The buildup problem didn't lessen but it didn't seem to have gotten noticably worse, either. I was starting to water my Mtssa. tonight and saw that the buildup (or whatever) has gotten worse now, and also a crystalline-looking coating has accumulated on the base of the pseudobulbs. I also saw some yellowish-brown patches along with the white. Some of the leaves are yellowing, too.

I would appreciate help from any of you who know what is going on and what I can do to solve the problem.

Thanks in advance,
Vicki