Brown Spot with Yellow Leaf on Dendrobium
 

Hi all,

I am hoping someone can advise me on how to properly treat my Dendrobium. Monday I noticed a small yellowing spot on the center of a leaf. I decided I would keep an eye on it and look it up. I believe it might be some kind of bacterial rot/spot but I am not sure and I do not want to treat incorrectly and make things worse.

I have attached two pictures. Monday there was a spot closer to the tip of the leaf. Yesterday there was the second spot closer to the center of the leaf. Both spots have darkened in color and the leaf has turned yellow. There is a green ring around the spot.

The cane is still the correct green color, all leaves are their normal green, roots that are sticking out of the medium and pot appear to be strong and healthy. I have never had problems with this orchid before. The leaf is on the cane that grew last year, but failed to bloom this year.

If anyone can help me figure out what has caused this and how I should best treat it, I would greatly appreciate it. Thanks!

People call that "mystery ring" on dendrobiums, although yours isn't quite round to be called the ring. I believe it's the same stuff regardless.

I have no idea as to why it happens. There was a thread about this and no one knew why, only confusing and incorrect guess and assumptions.

Being a dendrobium lover, I hate it when this happens to my plant. I had it happened to two of my dendrobiums and they happened to be one of my favorite. super healthy plants for a few months. as the new canes mature, these mytery rings started to show up. I just cut the affected leaf off and hoped it wouldn't come back whatever they were.
Well, they did show up on other leaves.
I cut off the leaf again. eventually the cane became bare at the end. lol
In fear of spreading to my other dendrobiums and not knowing what it is (other than it spreads really fast within a plant), I just got rid of the affected plants.
Never seen any of these rings ever since.

My advise would be isolate this plant away from others. Cut off the affected leaf and keep a close eye on this plant for any more rings to appear.

Thanks NYCorchidman. I isolated it from the others before posting. I will cut the leaf off in the morning. Should I be proactive and remove the cane in an attempt to save the plant? I hate to lose it, it's my only mini Den. It's also growing another cane right now too. Do you think maybe if I move it outside to grow away from all the others that might be an option too?

I wouldn't cut off an entire cane unless the cane itself is rotting.
Just watch the plant for any more spots to appear and remove them.
If it keeps on going on, I would toss the plant.
Worry of anything spreading onto other plants is one thing, but let's say after losing all the leaves, the plant is basically done.

If you have a seperate room where you don't have orchids, then you can keep it there and see what happens.

I just don't have enough patience to deal with something like that. I keep what grows and flowers well. Nothing else stays.
There are so many orchids and plants to choose from out there anyway! ;)

Thanks, I have isolated the plant. There was a keiki growing beside it and I noticed a small spot on its oldest leaf. I removed the leaves and applied cinnamon. Both plants are now being watched.

Out of curiosity, I dropped the leaves off at the Purdue Plant Disease testing lab today. I will repost when the results come back in case anyone else has this problem in the future.

Wow~ I would love to know the lab result!

Yes, I would love to hear the result as well.

I had the same problem with one of my dens. Did not have the heart to toss it out, so cut out the affected leaves and left it in the basement where it can get natural light. Still hanging in there. Really looking forward to the lab results!

Do you think it just may be sunburn or too much light?

No. The leaf will eventually drop off. And, other leaves will also have the same fate. At least, that's what happened to mine.