Rhyncholaelia glauca with dark patch on rhizome.

[BrassavolaStars]

Hello all,

I thought that I was done with rot after putting the orchids in the greenhouse but alas, I may be wrong.

While I was repotting my Rhy. glauca I noticed it has a dark region on the rhizome. I am worried it may be rot. It’s on the older part of the rhizome. Is it rot? What should I do? The area isn’t too soft, but a finger nail can go through it a bit.

[Roberta]

I think you're correct to worry about that one... the fact that it is in the rhizome and also into some of the pseudobulbs looks to me a lot like the black rot that's a killer. It looks like the part of the plant on the left of the farther-back photo doesn't have it, and has a healthy-looking lead. (It also looks like the part with the black is the back part of the plant) If I have correctly interpreted the photos (a bit small to be certain) this may be time for surgery (and you know I don't jump to that treatment very easily). If the section in the rhizome in the middle of the plant looks clean, that would be the place to cut - either a well-sterilized shears or a single-edge razor blade. If, after you cut you still see black in the rhizome, try to go a little further toward the "front" to get to clean tissue - hopefully it hasn't got too far.

[BrassavolaStars]

Thank you for your reply.
I guess I’ll get out the cutters. Hopefully nothing else was infected. How does this stuff spread? I did soak this plant before repotting and finding out about the rot. Would I have spread it to the healthy sections too by doing this?

[Roberta]

Originally Posted by BrassavolaStars

Thank you for your reply.
I guess I’ll get out the cutters. Hopefully nothing else was infected. How does this stuff spread?

I honestly don't know... it just shows up occasionally. I have never had it go from plant to plant, but when I see pseudobulbs dying from the bottom, alarms go off because it can take a plant pretty quickly. I have to guess that pathogens are just "out there" in the environment, a healthy plant usually can shrug it off but another one gets infected. An insect bite? A cut? Or??? Just like people... why does one person swimming at the beach end up with a flesh-eating infection and nobody else does?

Just do use good hygiene practices... like putting down some newspaper so that you don't get pathogens on the surface underneath (a lot easier to prevent transfer than to try to clean after) Rubber gloves if you have them, otherwise wash hands really well afterward.

[BrassavolaStars]

Here is a cross section of the rhizome where the black section was. I already cut off the section that had no dark areas.

[Roberta]

Originally Posted by BrassavolaStars

Here is a cross section of the rhizome where the black section was. I already cut off the section that had no dark areas.

That looks quite clean. So whatever it was, didn't get far. Which is good. The clean part of the plant is the growing area - the front, so I don't think there was any harm done, even if some of the dark part was OK... there weren't a lot of roots in that area. If it looks like the piece in the picture has potentially active "eyes' you could pot it up and see what it does. Dust the cut on the clean part with cinnamon, should be fine.

[SouthPark]

Originally Posted by BrassavolaStars

How does this stuff spread?

Some organisms are just around all the time. Growing techniques like choice of media, amount of air circulation, frequency/rate of watering, occasional allowance for pot dry-out etc ----- can cut down or even eliminate issues like that.

History can be important too - such as where did the plant come from? And how long have we had it for, current growing conditions etc.

If it is rot, then one approach is to apply a treatment that hopefully can deal with whatever is causing it. Over here, part of my arsenal (which I rarely had to use) is "yates anti-rot phosacid", mancozeb, cleary's 3336. Isolate the plant too - just in case.

What media did you use for growing this one?

If the rhizome remains firm, then it's possible that it's not rotting, and that would be nice.

Also - take a look at this link - which involves you too .... Cattleya Claesiana hybrid with black patch on pseudobulb

[Ray]

This is going to sound like an ad, but treat the plant with Inocucor Garden Solution monthly, and you'll not see that again.