Fungus on rotting mount

[Maryanne]

Oh, I do feel your anguish. if the rot is inhabiting both wood mount and plant, then the coming colder, darker winter weather is not going to help the plant. ( 6 months to spring!) If it was my plant, I would try the move, being careful to not ruin any good roots, giving a fresh mount, basket or pot. Orchids like 'fresh' media. You could try neem as a fungicide, as it is readily available and is said to be effective on fungi, and other microbes. (but check the bottle or other resources to be sure you agree with the choice.)

The plant will be in a holding pattern until March - April.

Anther method to try is to use all perlite in a pot to re-pot I've done this for back bulbs and had success in getting them to root.

Obviously, it's your choice what to do, but doing nothing might get more of the same results.

I wish you the very best of luck with your R. digbiyana
Keep us posted
Maryanne

[estación seca]

I myself would not pull it off the mount so as not to do that much root damage going into winter on the east coast.

Most fungus detest acidic pH. Most dicot roots tolerate acidic pH better than do most fungus. I would consider mixing a vineger-water solution with a pH of 2-3 and soaking the plant in that for 15 minutes. Then rinse with plain water. That should kill most of the fungus and leave the roots alone.

In this situation I would also consider hydrogen peroxide. Water the mount thoroughly so the roots are wet. Then spray 3% hydrogen peroxide (the standard concentration sold in drug stores) from a brand new bottle. Keep doing it so the roots and mount keep dripping and dripping. Let it sit for 5-10 minutes and rinse it off.

I think either of the two above would cause less root damage than pulling it off the mount.

[Ray]

In my experience, Rl. digbyana can take as much light as you can throw at it, and bloom best when they get a LOT.

Strip it and remount or strap it on another - both work.

[malteseproverb]

So I decided to do the acid treatment that ES suggested first by using citric acid since I had some lying around. I did do that, but then I thought about how there are several new roots coming off a new growth and why would I wait to repot it if those could be easily established in a new pot immediately. And I'm happy to say I managed to remove it from its mount with almost zero root loss! I think I lost a couple of roots max (you can see the denuded mount in one of the attached pics).

The soak helped loosen the roots, so I manually removed the roots off of the top of the mount to get a better angle on the rhizome. I used an offset spatula (often used in baking) to gently pry the rhizome from the mount, and because the exterior of the mount was soft enough, I could basically scrap off the wood from behind the rhizome using the spat along with the rest of the roots all in one go and left everything in tact (check out my progress shot). The entire thing just lifted off and the mass of roots at the bottom came along with it. I repot it in terracotta with some peanuts and large orchiata for now.

My only question now is whether or not I should cut off the parts of the rhizome that seem to be getting mushy and dying. There is one side that is probably just going to die no matter what (highlighted in red in photo 3). Should I get rid of that now because the rot may spread, or should I let the plant try to pull on those growths for strength as it recovers from its minimally invasive surgery? I could probably at least cut off that bit to be safe, but I don't want to do more damage than I have to.

Thank you everyone with your help so far!

[estación seca]

I cut off the minimum necessary. But we don't know what your exact problem is. If it's caused by inadequate water due to poor roots there won't be any infection spreading up the rhizome.

[malteseproverb]

That's my thought, too. Wait and see as it adapts to a new pot that isn't covered in fungus...