Cymbidium Disease

[rodrigo]

Rainy season just ended in Costa Rica in November.

Now, on several of my Cymbidiums rotten growing shoots have appeared.

You cannot tell from just looking at the growing shoot as it looks perfectly healthy (in its begining stage), but if you pull on the youngest leaf it comes out with a rotten inner part that has a foul strong tobacco-like smell

Here are some pictures that illustrate my problem:

This is how the base of the shoot looks after separating from plant. "Wet" looking with foul strong tobacco-like smell:


The shoot looks perfectly healthy to the untrained eye


The inner leaf comes out easily if you pull on it. Look at the "wet looking" bad and smelly inner part of shoot:


This is the emergency treatment I followed:
1- "Amputated" the bad bulb from plant.
2- Treated wound with a systemic fungicide for about 5 minutes.
3- Sealed wound with a fungicide / bactericide sealer paste.

This is the plant after treatment:


Observation:
It seems to attack "juvenile" foliage shoots. Bulbs seem to be immune at the initial stage.

Questions:

1- What disease is this? It looks like a fungus but which?

2- How can I effectively treat the diseased plant? The plants seems to be recuperating after my emergency treatment. You can look at new shoot coming out. But I'm not sure if plant is still contaminated.

3- How can I prevent it from happening again? Or at least minimize the chance of re-occurring.

Thanks for all your help on this issue.

Regards,

Rodrigo

[RosieC]

Sorry I can't help, hopefully someone else who can will come along soon.

[Cym Ladye]

Rodrigo,

This is black fungal rot caused by water staying too long in the young growth, lack of adequate air circulation and mild ambient temperatures. It can progress from the young bulb down to the roots and on to subsequent bulbs.

Prevention is the best measure:
1) Keep plants well spaced to allow adequate air movement. Some hobby growers space the plants so that the leaves from one do not touch the leaves of the surrounding ones.
2) Water only in the morning.
3) In the winter, try to keep the plants drier. My season is cold and wet but with slightly tilted benches and good air movement, I do not have the problem.
4) Mild ambient temperature along with water in the young growth allows the fungus spores to grow and the rot occur.

Care:
1) Cut with a sterile blade back to a healthy pseudo bulb.
2) Treat the cut with cinnamon (or fungicide of choice if available) and allow to air dry for several days.

If not caught quickly and treated, this rot has the potential of killing the entire plant.

CL

[orchids3]

Agree with what Cym Layde has to say - had a few cases of this myself this spring. I enclose the sides of my growing area during the winter - the problem occoured because I did not take away winter protection. It restricted airflow and I got rot that looks a lot like yours in a few cymbidiums.

[rodrigo]

Thanks to all for your observations and knowledge.
I suspected it had to be related to excessive water.
Happy New Year to all !

Rodrigo