Fungus on rotting mount - Orchid Board

malteseproverb · #1 09-20-2021, 02:55 PM

Does anyone have any advice on how best to remove this orchid from its mount with the least possible amount of damage?

I've had this rhyncholaelia digbyana for about 3 years. When I got it it was in bad shape. I mounted it and it did very well for a while, slowly getting bigger and bigger. Last year I noticed this scummy looking fungus growing on the bottom of the mount. I repeated treated it with physan, sometimes sprayings, sometimes soaking over night. Nothing happened except that most of the roots died. The mold spread to other parts of the mount, and I realized it was coming from within the mount.

I decided to ignore it for a bit, give it more sun (it gets TONS of sun), but then recently I noticed one of the latest growths has just turned to mush. I know it's just a matter of time now before it takes the whole plant.

I would like very much to save it, as it's very sentimental to me. I inherited it from my grandmother-in-law, and it's the national flower of Honduras, where my mother is from. Any advice would be very appreciated!

estación seca · #2 09-20-2021, 07:01 PM

Full sun in summer is too much for this plant. It grows under the canopy. It gets more light in winter when the trees drop their leaves. I think your problem is heat, sun and not enough water. The molding mount wood is incidental.

Also, how are you fertilizing? Loss of new growths can be from not enough water, too much sun / heat or not enough calcium.

malteseproverb · #3 09-21-2021, 10:53 AM

I actually gave it less sun than last summer this year because I was trying to see if it would help. It did not. It's doing far worse this year than last year. It's been in indirect light with my other, very happy mounted plants including a bulbo. I mainly stated that it is getting plenty of light to stave off a typical response to give it more light, which I know it cannot possibly need at this point. I'm attaching a photo where you can see how the problem looks on the plant. This brown rot is climbing up the rhizome and has steadily killed off many old growths for months. Now it got to the newest cane, so it can't be just regular old growth die-off. The new growth was mushy in the stem before it bent like that.

I really hope you're right that I don't have to remove it from the mount. Giving it even less light would be so much easier if that is the solution! But I already tried a few things because I was kinda in denial that the mold would be a problem, and I'm afraid that I'm just putting off the inevitable at this point.

Side note, I really wish the photos were higher-res on here, it is so hard to clearly show what is going on...

estación seca · #4 09-21-2021, 12:30 PM

Contact the microbiology department one of the universities or your county agricultural extension. See whether they could try to look at it under a microscope and find out what the problem is.

You could also send photos to Cattleya nurseries and see whether they have any ideas.

malteseproverb · #5 09-21-2021, 01:02 PM

Are you saying you think it's coming from the plant and not the mount? Or that it's infected the plant and my repotting intervention won't help? I'm not sure Philadelphia county is going to care about my moldy houseplant. This city cannot even pick up my trash within 48 hours of my designated trash day. Just curious why you would suggest that instead of potting it up. I actually work for a university, maybe they would be interested but is that a service commonly offered or just something grad students occasionally attempt? I'm not finding any info online about it at my university.

By the way, this mount was sitting in my grandmother-in-law's basement for who knows how long before I decided to attach an orchid to it. And then I usually keep this plant in my basement under grow lights during the winter. So I assumed that's where the mold came from. I don't know if that makes a difference.

Maryanne · #6 09-21-2021, 02:32 PM

Hello 'Proverb:
I have quite few wood mounted plants. Wood rots, it's a fact. At some point the orchid needs to be transferred to a fresh mount or a pot or basket. I wish you had asked this in spring, it would be easier to make the switch.
Without having this in my hand and feeling the wood issues, I'll just give some suggestions. It's up to you to decide your move. Is there enough good healthy green to support the plant, with good roots? Can you peel, scrape or chisel off the bad wood gently?
I did a similar move this summer to a Nagelliella mounted on plum wood - I picked off as much rot as possible, and left as many roots intact on sort of OK wood, then I chose a new chunk of mountain laurel branch to tie it to. (Mountain laurel resists rot for a long time) Good roots and newly forming roots should be placed on good wood, tied securely using a cover of thin layer of moss to protect them. (I use soft acrylic yarn because I don't like monfiliment - it can cut roots) Set in the shade to recuperate. You could use a seaweed solution to water if you like. No mountain laurel? Try fresh oak or a new basket. Using an old chunk of wood as you describe from the 'basement' is not advised - mildew grows in basements. : -( It's now Fall, so growth will be slow, maybe try some supplemental light if you can.
Channel your Abuela for help!
Good luck with your 'sentimental journey!'
Maryanne

estación seca · #7 09-21-2021, 02:43 PM

Many university bio departments love interacting with the public, answering questions about things people find. I send people there all the time to identify bugs and weeds. I know people who've had pathogens identified there.

The county ag extension is a cooperative program between a university and the county. They were set up to advise farmers. Your county still might have one. Look for "XXXXX County Agricultural Extension Office" where XXXXX is the name of your county.

Check the diseases page at the Saint Augustine Orchid Society Web page.

Maryanne · #8 09-21-2021, 02:53 PM

Folks:
I forgot to mention I also work a a university. The Extension service may have a plant bio lab, or maybe Microbiology, but generally they do farm and landscape types of consultation. If there is a campus greenhouse or conservatory that keeps orchids as part of the collection, with a friendly Director/Manager on board, that may be a better place to consult.
Good luck, once a gain,
Maryanne

Roberta · #9 09-21-2021, 03:03 PM

When I have a mount rot (and they generally do, eventually) I just tie the whole thing to another mount unless the plant comes loose easily when I cut the "strings". The roots find a "friendlier" environment and keep on going on the new material. If you can break away disintegrated parts of the mount, you'll also get rid of some of the rot. I don't think I have had a rotting mount spread to the plant, though. If there is that much rot within the mount, you can probably crumble much of it away. Others on the Board have experience with "real" fungicides... might be useful to bring out bigger guns. (I haven't used them so defer to those who know more about the products)

If I have something that I think would do better in pot or basket, or has grown off the mount, I'll drop the whole thing into the new container, fill in with some large bark.

malteseproverb · #10 09-22-2021, 11:42 AM

I know I'm so mad at myself for not just doing it in the spring... But again I was in denial and thought I could ride it out. Not sure our horticulture school does much with orchids. It's out in the burbs, and I work remote anyway. I'm just trying to figure out if there is any benefit to finding out the microbiology of the fungus over just trying to get the orchid out of this situation. If I remove the plant from the mount and it's still present in the plant, I can see how finding out the cause and treating it specifically could help.

This is a catch 22 situation I guess. Either I kill half the roots by chopping it off the mount, or I continue to chance it and let the rot consume it? Seems like either option have a high probability of killing the plant, probably the latter more than the former though. Attaching it to another mount seems like it would be an option except that there is already damage occurring to the rhizome and spreading quickly. Strangely, despite all the fungus, the mount is not particularly easy to break apart. It's remarkably strong and in tact.

I think I'm just going to put it in a pot after this. I wonder if it would prefer that anyway since it's getting so sick on the mount. I'm going to attempt the surgery today and will update this thread on how it goes.