HU, It looks like you have a pretty sick puppy on your hands. How long has it taken the plant to reach this stage of its ailment? Have you brought any new orchids or other kinds of plants into the house, or the same room with this plant recently?

I'm no expert on plant diseases, but there are some things on your plant that makes me want to say it might be virused. To be specific, the mature green leaf with the light yellow area in its center that is growing away from the camera has some crinkling, and pitting that looks to me like it might be virus. The big yellow and black leaf in the foreground looks like it may be virused, and the leaf in the bottom left corner of the photo has a spot that looks like virus. Virus can take a very long time to manifest itself, and then it appear suddenly and the plant dies quickly, or the plant may show symptoms and die very quickly.

There is no sure cure for virus in orchids, unless something has come along since I left my close association with the business. I would check my other orchids closely to see if they show symptoms. If you have brought new plants into the growing area, they could be the culprits that brought it in, but it could also have been in that plant when you purchased it. It also could have been in your other orchids or other plants for a long time.

There are virus test kits on the market, but testing a plant would only mean you would know it was virused. There is no cure that I know of. You would need to test all your plants if one tested positive, and I think the tests are pretty pricey.

I hope it is not virus, but think I would start with worst case and work from there. hopefully you will get other suggestions.

Let me throw in a bit of advice for all who may read this post. This is why you always hear us "old timers" constantly preaching...Razor sharp cutting tools that are clean and sterilized for every cut you make on your plants, and make clean cuts, not ragged tears.

I would agree with Bill's diagnosis. As to what to do next, if you have other phals, or even other orchids, I would isolate this one. Keep it as far away from the rest as possible. By all means, take it out of the pot and have a look at the roots. At least there appear to be plenty of aerial roots so the roots in the medium are probably fine but double check in any case. Remove any dead roots and change potting media if there is a lot of root rot. Cut off the mostly yellow leaf. Feed it well. Sometimes, stronger plants can overcome viral infections and continue to have a productive life.

HU, I hope you keep this forum updated about the subject phal's condition. Thank you.

Thanks for all your comments. i’ve decided to go for broke and cut off the two sickest leaves, and even pieces of other slightly dodgy looking leaves. I’ve put ground cinnamon on all the cut edges, and I’ve left the plant in splendid isolation in a bright, warm room. After a day of such drastic action, it’s uglier but not noticeably dying. There’s even a new flower spike forming on it.

Great. Keep the cinnamon out of the roots, I think you are already doing that. Did the youngest leaf turn yellow since your original post, where it looks pretty healthy?

I accident nicked the youngest leaf with my scalpel when I was amputating the really bad leaves. I’m keeping my eye on it. If it goes the way of the others, I’ll cut it off as well. The way I see it is that either I hack away at this poor plant or I throw it in the bin.

Exactly. I never give up on any infected plant. If it is ready for trash, it is better utilized for experimentation. Best case, it recovers, worst case it dies.

Now, if I had really expensive specimens that were at risk of getting infected, it would be a different consideration.