Getting rid of fungus on orchid mounts?

[nancy]

Greetings -
It has been an unusually wet summer, even for south Louisiana, and September is predicted to be more of the same - a daily soaking; sometimes days of drizzle. This too-much has led to an unexpected problem for me; I grow almost everything on a mount of some kind. I haven't had problems with orchids rotting (or liquefying), but am beginning to have fungus problems on the wood mounts themselves (mostly grapevine, also cork, catalpa, cedar, etc.). The growths include several kinds of typical mushrooms as well as some bract/tree-ear types; some even look like lichens.
In my arsenal I have liquid Physan, and Bordeaux and elemental sulfur powders - will any of these help? I suppose these are a type of mycelium, rather than what I think of as a typical fungus.
If not, then what can I try?
Thanks - Nancy

[Ross]

I get the same thing (small white fungus/mold) on certain mounts in my terrarium. Reason is the high, high humidity. I use a small brass brush from an auto supply place. They're normally used to remove rust. I spray liberally with Physan 20 then scrub any spots that I can without causeing plant or root damage. I have been doing this daily for a while now and seems to help. Strong air movement is the cure. I started running a fan through-wall with this large terrarium and a few hours at night has done wonders at slowing it down. As soon as things dry out later in the winter it should go away till next time.

[nancy]

Hi Ross -
Well, I grow outside, so increasing air flow is not up to me. When I say 'mushrooms', I mean stems with caps 1/2 to 6" across! Every color in the white/brown/grey spectrum. Wish I knew which ones were edible. The 'tree-ear' types, some of them are like brown rubber, very difficult even to scrape off with a putty knife. Same with the things that resemble lichens, smooth coating on the wood with frilled edges. Now, doesn't that sound nice?
What I think I need is a RoundUp for mushrooms. That won't hurt my orchids. While I'm dreaming, can I be taller, too?
I'm a little afraid to go after some of these outbreaks with a brush, because many of the wood pieces are literally covered in root and foliage, but I'll try your method on some likely prospects. Can't wait until the humidity drops below 95% - ooooooohhh. RH much below 80% is pretty rare here even in winter.
Cheers - Nancy

[Ross]

Originally Posted by nancy

Hi Ross -
Well, I grow outside, so increasing air flow is not up to me. When I say 'mushrooms', I mean stems with caps 1/2 to 6" across! Every color in the white/brown/grey spectrum. Wish I knew which ones were edible. The 'tree-ear' types, some of them are like brown rubber, very difficult even to scrape off with a putty knife. Same with the things that resemble lichens, smooth coating on the wood with frilled edges. Now, doesn't that sound nice?
What I think I need is a RoundUp for mushrooms. That won't hurt my orchids. While I'm dreaming, can I be taller, too?
I'm a little afraid to go after some of these outbreaks with a brush, because many of the wood pieces are literally covered in root and foliage, but I'll try your method on some likely prospects. Can't wait until the humidity drops below 95% - ooooooohhh. RH much below 80% is pretty rare here even in winter.
Cheers - Nancy

There are chemicals that will kill the fungus roots and plants, but will undoubtedly kill or mame you 'chids as well. I get the white true mushrooms, too, but I stick with my regime cause it hasn't hurt the 'chids, even though it's not solving the fungus problem long-term. After all, you have dead wood and the micro organisms are only doing what they were designed to do. Not sure it truly hurts anything, just looks like heck.

[nancy]

Hi Ross - update on this...I talked this over with our county agent, who said that a fixed-copper fungicide would be the most effective on mushroom-types. He mentioned a few names of commercial products used on golf courses, etc., but said they ($350+) were not any more effective than some of the other products. So I mixed up some of the Bordeaux powder this morning and applied it. 9T/gallon, so it was the consistency of thin mud! I applied it about 7:15, and it rained at about 8:30, then again at 1:00 and 3:00, so we will see.
I think the Bordeaux is one of the older fungicides that is typically recommended for use on orchids, so I hope it will do no harm.
Not sure if I need to reapply before the 10-14 days is up, since it is just consistently raining almost continuously.
I'll let you know. Regards - Nancy

[Ross]

Originally Posted by nancy

Hi Ross - update on this...I talked this over with our county agent, who said that a fixed-copper fungicide would be the most effective on mushroom-types. He mentioned a few names of commercial products used on golf courses, etc., but said they ($350+) were not any more effective than some of the other products. So I mixed up some of the Bordeaux powder this morning and applied it. 9T/gallon, so it was the consistency of thin mud! I applied it about 7:15, and it rained at about 8:30, then again at 1:00 and 3:00, so we will see.
I think the Bordeaux is one of the older fungicides that is typically recommended for use on orchids, so I hope it will do no harm.
Not sure if I need to reapply before the 10-14 days is up, since it is just consistently raining almost continuously.
I'll let you know. Regards - Nancy

Nancy, how has this worked? I'm thinking of getting some Bordeaux and applying to my mounts, but roots are involved on several so I can't go too strong.

[nancy]

Hi Ross -
While considering that our climates are pretty different, the fungus is just as alarming, I'm sure.
Treating with the Bordeaux the first time pretty well stopped all the cap-type mushrooms. I did re-apply a couple of days ago, just to be anal. It continues to rain a lot, and Humberto gifted us with about 7 inches.
The bract fungi and the lichen-looking stuff seems pretty unaffected. This might be because they are more substantial/different texture than the mushrooms, which kind of dried up overnight.
The stuff that looks like lichen really bothers me, because it is spreading over the whole wood as well as creeping over the tops of some roots. A couple of friends in this area are having the same problem with this kind of fungus.
I'm going to use the Bordeaux a few more times - BTW, it is kind of hard to apply with a sprayer because the consistency is so muddy; the nozzle clogs really quickly and you have to keep shaking it up...
A guy in our orchid society who grows semi-commercially (and has won lots of AOS awards) uses Merit (around $250/ltr.) but it is used very diluted - a few drops per gallon; he says it is extremely effective on fungus and rots of all kinds. If we can get a dozen or so people to chip in, we might spring for a liter to share.
In the meantime, at least for the mushrooms, the Bordeaux seems to be working, even with the rain continuing.
I asked the county agent if I could use it straight (as a powder) because I just hate to add more wetness to my plants, but he said it is only effective applied diluted.
I'd appreciate any wondercure you find, too.
Regards - Nancy

[Bolero]

Let us know what works for you nancy - it will be interesting to hear your progress in getting rid of the problem.