Green Dot and yellow leaves on Dendrobium

[NYCorchidman]

but I'm not 100% sure.

I love this type of dendrobium and have quite a few.
My experience has been that some dendrobiums are sensitive to environmental changes from nursery to home, and lose some bottom leaves on both old and new canes while some never lose any leaves when first brought home.

Then there are some dendrobiums that lose all the leaves except for three or four top leaves on each cane.

Of all the dendrobiums I have, only three displayed this mysterious ring symptom. They either stay green or turn black. Funny thing is even when the entire leaf turn yellow, the ring stays green.
One particular den had lots of these rings and I tossed it out in fear of having whatever it is might spread to my other plants.

The other two showed only one ring each. Of these two, one was shedding lots of leaves all of sudden and only left top four leaves. Of all the leaves shed, one leaf had this green ring. The plant is growing a new cane and two keikis.

The other one has lost one or two bottom leaves of all the canes. One of the lost leaves had this green ring with black center. It had some very very small fungal spore structure on the black part. I cut that leaf and burned on the stove top.

So far, none of my dendrobiums are losing any leaves but all are growing new canes and some even spikes.

So I would suggest anytime you see this green ring, remove the leaf before the spores develop and spread.
Also, keep a close eye on this dendrobium and see how far it progresses. If the leaf shedding stops when the top few leaves are intact, then I wouldn't worry too much. If not, then best toss the plant.
Just my opinion.

[JDawggie]

Well, when repotting the plant and examining the roots, they did not look great -- not horrible, but not not even good. The one thing that DID concern me was that the bottom part of the cane (even the new growth) -- was turning brown and a bit spongy...I read the other post on this strange happening with the "rings" that calypso sent (thank you much BTW) and I am leaning toward a fungi, but it seems there is still question as to what it was. No doubt the post looks like the same issue my plant had. However, my plant was purchased months ago -- so if it were a virus, it had a very long incubation period, not saying it is not possible, and I am NO expert, but seems more like fungi to me after reading a bunch!

Anyway, due to the canes at the bottom beginning to mush ..and the overall uncertainty of what is going on, I decided to "retire" the plant...at least I got some good pics when it bloomed last. I just do not want to take a chance with it destroying my other plants (hopefully it is not too late as it is!!!!).

Thank all for you help and advice etc.

Jared

[NYCorchidman]

Originally Posted by JDawggie

Well, when repotting the plant and examining the roots, they did not look great -- not horrible, but not not even good. The one thing that DID concern me was that the bottom part of the cane (even the new growth) -- was turning brown and a bit spongy...I read the other post on this strange happening with the "rings" that calypso sent (thank you much BTW) and I am leaning toward a fungi, but it seems there is still question as to what it was. No doubt the post looks like the same issue my plant had. However, my plant was purchased months ago -- so if it were a virus, it had a very long incubation period, not saying it is not possible, and I am NO expert, but seems more like fungi to me after reading a bunch!

Anyway, due to the canes at the bottom beginning to mush ..and the overall uncertainty of what is going on, I decided to "retire" the plant...at least I got some good pics when it bloomed last. I just do not want to take a chance with it destroying my other plants (hopefully it is not too late as it is!!!!).

Thank all for you help and advice etc.

Jared

Without microscopic examination, no one can be sure as to what it is.
Fungus generally spreads fast given the condition is favorable for it to do so.
Virus in plants can spread fast, but usually "spread" is not the best term to use on virus. Virus needs the host to survive in the first place.
Sever case senario is the death of the host plant as the virus takes over the host plant. but it's more likely living with the host plant gradually weakening it. This may or may not kill the plant.
Also, very often, virused plants do not display any symptoms, yet the plant is still capable of infecting other plants, so using sterile tools on plants whether they look healthy or not is very important.

On a different note, if you really like the plant, you can try and save it. A few of my dendrobium came with rotten roots. I through away or cooked the media in the oven to kill everything (just dumping was not good enough for me sometimes hehehe). cut away all the dead roots and wash good. soak in chemicals following instructions.

then just keep the cane in a dry container until you see signs of keikis bursting out. It worked for me.
It's up to you.

Alternative will be, only cut the roots that you know for sure are dead as sometiems dead looking brown roots are not really dead. you can feel each root (I know it's time consuming) and if roots feel somewhat firm at all, then do not cut, which cutting away all the mushy ones. wash with water then soak in the chemicals.
dry completely and then pot up in a clean media.
Water only sparingly or just mist heavily everyday.
When you see new growth starting, then you can water normally.