Black Rings on Dendrobium-Phalaenopsis Hybrid

[KristenJ]

Hi all,

I have a Dendrobium-Phalaenopsis hybrid that has been having weird problems off and on for almost 2 years. I've asked around on Orchid Board and at Orchid Shows and tried just about everything. First it had browning tips. The suggestion was fertilizer burn, so I started doing flushes and it seemed to be okay. Then I moved to a place with softened water. And it had weird spots at the tips of the leaves. The suggestions were bacteria/fungus, so I started treating with Physan 20. It went away during summer/fall, but started up again during this winter. (This is a very long story short.)

I described everything that has happened with this orchid at the last orchid show, and they suggested that I try giving it a winter rest. I did this, and all of the leaves on the oldest cane turned yellow. Then today, I noticed the weird black rings (shown in the picture).

Does anybody have any idea at all what this could be? I would appreciate any help with this one. Thank you!