Snow mold - Orchid Board

ScottMcC · #1 (**permalink**) 06-12-2006, 10:09 AM

I seem to have a pretty good bit of snow mold going on my big catt. I've already got plans underway to repot it into s/h (thanks Ray), but in the meantime while I'm waiting for my supplies to arrive, would it be a good idea to give it a hit of physan? The way I see it, 2 doses (one now, one when I repot) is more likely to take care of the problem than just one, but I don't want to hurt my plant either.

I know the main issue is getting rid of all the infested media, as the mold is primarily infesting the bark, not the plant, but I just thought this might kick-start the process by reducing the pathogen load a little while I'm waiting for supplies, and would of course give me the benefit of a second dose. Of course, if I'm off base here, let me know, because like I've said before, I'm pretty new at this!

Thanks in advance!

Tindomul · #2 (**permalink**) 06-12-2006, 01:19 PM

Why does the mold grow? Over watering??

ScottMcC · #3 (**permalink**) 06-12-2006, 02:44 PM

I found mention of it briefly at this link:

http://orchidweb.org/aos/MessageBoar.../ROA200605.PDF (don't know if you can get there from externally, you may have to log on to the orchidweb.org forum and then go here http://orchidweb.org/aos/MessageBoar....aspx?tid=3374 )

From what I can tell, it's a result of the bark mix breaking down more than anything, but I could be wrong.

Anyone had any expereince with this problem???

Thanks!!

Tindomul · #4 (**permalink**) 06-12-2006, 04:59 PM

I just read the little article you sent. For those who can't see the link or don't want to look for it, it says:
Snow mold is a fungus called ptychogaster. It spreads through potting medium, often visible on top of the medium you are using (tree fern or fir bark) and around the drain holes of you pot. It leads to drying out of your orchid as the mold starts to grow on the roots of the plant and is water repellant, so water barely reaches the roots.
According to the article you repot the plant, remove and destroy all mold and potting media. Remove from the roots and treat the roots with Physan or RD20.

It be interesting to see what other people with experience have to say.

Thanks for the link Dr. Scott.

ScottMcC · #5 (**permalink**) 06-13-2006, 11:11 PM

update 1: yesterday I gave the catt a good shot of the physan. I mixed up a quart of water with 1/2 tsp of physan, then poured it all over the plant. so far everything seems ok.

Oscarman · #6 (**permalink**) 06-13-2006, 11:29 PM

I would suspect that the snow mold is a result of the media breakdown AND the resulting lack of air within it.
I would give the entire pot an extended dunk in a Physan solution to allow it time to fully infiltrate the media.
If the mold is indeed water repellent, a small amount of plant safe detergent may be in order to help reduce it's surface tension and allow the Physan to penetrate.

ScottMcC · #7 (**permalink**) 06-14-2006, 08:40 AM

that's going to be phase 2 of my plan...

as soon as I get my s/h kit, I'm going to soak the plant in concentrated physan (1 tablespoon/gallon) for 5 min, then unpot, remove all signs of the mold, divide, rinse with concentrated physan, and repot in s/h. they actually recommend something like this on the physan product insert as just part of the routine repotting process.

sound good?

ps, further update: I just looked at the visible areas of mold on the surface of the medium, and around the drain holes, and they have definitely regressed since undergoing phase 1. so I think it's helping to at least kick-start the process.

(edited to add the 2 pictures)

Tindomul · #8 (**permalink**) 06-14-2006, 01:54 PM

Keep us updated. All this is new stuff to me.

ScottMcC · #9 (**permalink**) 06-14-2006, 03:46 PM

Quote:

Originally Posted by Oscarman

If the mold is indeed water repellent, a small amount of plant safe detergent may be in order to help reduce it's surface tension and allow the Physan to penetrate.

Biochemist mode ON:

Physan appears to be a surfactant as is, so I don't think any added detergent is necessary. This is evidenced by the viscous character of the concentrate as well as the ready foaming when mixed with water. The structure of it (an aromatic amine) also leads me to the same conclusions.

Chemist mode OFF.

I think the real solution is going to be removal of all the old potting medium (standard orchid bark mix) and debridement of any affected areas of the roots. The Physan should just help the process along by getting rid of smaller collections of fungus which are retained, and the first dose appears to have had the exact effect I wanted: reducing the total pathogen load and slowing the growth of the fungus some. But we'll see. The real test will be next week and thereafter once it has a chance to reestablish in its new pots.

Oscarman · #10 (**permalink**) 06-14-2006, 06:04 PM

Very impressive

........are you a biochemist?

Let me know how the s/h works with you plant - I also ordered some supplies from Ray (yesterday actually) to move my phals into. If all goes well, I will probably change most my plants (catts, paphs, phrags) to it.

I am really interested in the use of it for seedlings, as I have many flasks.

Are you going to use K-L-N upon repot?