Please help me ID this rot

[turock]

Hi all, one of my dendrobiums has had yellow, brittle leaves for a while now, and I noticed that the psuedobulbs were brown and rubbery at their base. I decided the plant was a goner and cut off the most affected pseudobulb. Most of it was black and spongey:

I cut the other pseudobulbs afterwards, and they were a brownish green and looked like they were in the process of drying out.

It's obviously too late to save this Dendrobium, but I'm seeing something similar on an Encyclia that I like quite a bit. The base of its new, mature pseudobulb turned brown and completely separated the bulb from the plant. I cut further up the bulb and noticed the brown was spreading into the rest of the growth. Some of the other growths appear to be developing some brown at their base as well.

What is this, and can anything be done to stop it?


Sent from my iPhone using Tapatalk

[jkofferdahl]

It looks like a fungal rot to me. Treat the plants for fungus and repot.

[bil]

Originally Posted by turock

Hi all, one of my dendrobiums has had yellow, brittle leaves for a while now, and I noticed that the psuedobulbs were brown and rubbery at their base. I decided the plant was a goner and cut off the most affected pseudobulb. Most of it was black and spongey:

I cut the other pseudobulbs afterwards, and they were a brownish green and looked like they were in the process of drying out.

It's obviously too late to save this Dendrobium, but I'm seeing something similar on an Encyclia that I like quite a bit. The base of its new, mature pseudobulb turned brown and completely separated the bulb from the plant. I cut further up the bulb and noticed the brown was spreading into the rest of the growth. Some of the other growths appear to be developing some brown at their base as well.

What is this, and can anything be done to stop it?

Where did the rot start? Top of the cane or bottom?

[dounoharm]

inspect every time you water, every one of your plants, then when something starts, you can catch it....I don't know about all you guys, but I can smell rot....maybe I just have a good nose for it!

[jkofferdahl]

Originally Posted by dounoharm

inspect every time you water, every one of your plants, then when something starts, you can catch it....I don't know about all you guys, but I can smell rot....maybe I just have a good nose for it!

Fungus and mold do have a certain odor to them which is quite distinct. Fortunately, it's been a long, long time since I had to smell it, which I feel certain is at least in part due to using more fans.

And I can't imagine NOT inspecting plants with each watering! To me, half the fun is in seeing the little changes you miss if you don't regularly commune with your plants.

[Sharon's Sheepdogs]

I'm sorry I didn't see this post earlier. Whenever I'm dealing with a rot which I need to identify, I go to the following two sites for help:

http://www.phelpsfarm.com/OrchidPestsandDiseases.pdf

Orchid Pests, Orchid Diseases

Most of the information in the first link comes from Sue Bottom at the St. Augustine Orchid Society. It is a great article and contains photos.

If you can't find your answer in the article, try the second link where Sue & other members provide additional information on the identification & treatment of orchid diseases.

Hope this helps.

[Selmo]

Most of the stem rots are caused by pythium or black rot, a fast moving fungus caused by warm temps, high humidity, and poor air movement. In turf or the grass in your front yard, pythium is a common disease in the summer when temps and humidity are high and forms at night when winds are calm and dew is heavy. It can be seen in the morning as a purple-gray ring of mycelium. Shows how same fungus looks completely different on different plants. Back to the problem at handed, isolate the plant, splashing water can move this to other plants, increase air movement for all your plants, and spray this plant and any others around it with a fungicide labeled for pythium (subdue, banrot, ect.) it will stop it in its tracks. You may need to spray every 7-10 days to keep this under control

[estación seca]

Note that most commonly sold fungicides will not kill Pythium. The ones Selmo mentioned will do so. Read the label.

[Sharon's Sheepdogs]

You can purchase a small container of Banrot from Green Barn Orchid Supplies. Due to the high cost of some of the better fungicides such as Subdue, I alternate Banrot with Monterey Agrifos every 90 days as a preventative for black rot. Both fungicides are systemic so the orchid is protected for long periods of time but you should not use the same one twice in a row or resistance could develop.

[azredsand]

Sharon---how are you using the Agrifos? What is the amount that you use? The directions are unclear as to how much to use. Thanks