fungus in media

[OhioBob]

I repotted several plants recently. Two of the orchids had fungal hyphae growing in the media. The dendrobium was in a rock/bark mixture and the mold was in chunks like it decided to grow on one piece of bark instead of spreading. The oncidium was in a bark only mixture and the mold was throughout the mixture. On both plants I had really good looking root systems with no dead roots.

Is this a normal situation and should I be concerned about the transplants? The onc went into SH and the dend went back into a rock/bark mix.

[BruceP]

Usually not a big deal. You may want to use a little Physan when you're wetting your potting mix and then from time-to-time as a spray or soak.

[Bud]

If you have healthy roots it means that the fungus and the plant has a simbiotic relations...and the plant is getting some nutrients from the fungus...if you have rotting parts in the plant due to the fungus then you must take action to eradicate it.
Some fungus are good for some orchids...maybe the fungus was with the plant since seedling...

[bballr4567]

I have one oncidium that has a ton of roots and they are covered in a little bit of fungus. There was not a single rotted root in and the plant has remained healthy so I figured it was a good relationship. I still use a little fungicide as it tends to smell funky so I use it to control that and try to not kill it off.

[camille1585]

Because healthy roots co-exist with the fungus does not necessarily mean that they are symbiotic. It could also very well be that the fungus only feeds off dead material, like bark.

[BruceP]

That's right, you can't see the 'symbiotic' fungus. The fungi/mold being described in this thread are those that otherwise inhabit moist places.

[euplusia]

Fungus mycels are everywhere. Most of them are not harmful to orchids, some may be useful. In its natural habitat mycels, lichens, cyanobacteria, mosses form biological crusts on bark, rocks and sand that are the essential basics for life and orchid nutrition.
In the pot however it shows that the medium is decomposing, thus releasing humin acids, keeping the air away and will lead to dying roots sooner or later.
I would consider repotting as long as roots are healthy.

[camille1585]

I once had some sort of fungus colonizing the medium somewhat freshly repotted Phal. Since it was a shame to toss good bark, I unpotted let the bark dry a few days, then repotted the Phal in it. The fungus never came back.

[Leafmite]

The bark was likely exposed to the fungus before becoming orchid bark or during the process, from other bark. Our last orchid society speaker pointed out that, years ago, orchid mediums were usually pre-sterilized but now they are not, due to the expense. He recommended the procedure before using it for potting.

[OhioBob]

Thanks for the information everyone. I thought the fungus was fine, especially when the roots all looked good. The plants are repotted so I will know soon enough if I did a good job. The dendrobium did not like repotting the last time and I was reluctant to do it this time, but when they are creeping out of the pot you need to do something.