Help, Mold!

[Ocelaris]

My Vandas are doing wonderfully air rooted but my oncidium genera, cattleya are molding at the crown, just 3 days into their new home and even though I cleaned off the organic material, they are wayyy too moist. I have lowered the humidity in their growth space ~60% during the day, less at night, and am venting fully at all times...

Does no one else have this problem? It's especially bad with the phrags, starting crown rot, even though leaf growth is decent. Should I just cut side holes in the pot to let more air in? I don't water but every 4-5 days or when no water is in the reservoir.

This is an ongoing problem, the roots of the phrags are very bad looking, no new root growth to speak of. I have one LC which is doing incredible (ok it's insane), but none of the others seem to be enjoying their semi-hydro in the same manner...

Should I clean up with Thiomyl or Physan? Air movement is pretty decent given my small area... the pots are tall and narrow though, well, relatively, they're Rays' 4.5" pots, which are maybe 7" tall? Relatively tall/narrow compared to the 5.5" which are the same height but 3" wider...

Thanks, Bill

[Becca]

Hi Bill! It isn't usually that a question will go un-answered this long. Perhaps your post just got over-looked. I don't have much of an answer for you since I am pretty new to things. I am having fungus issues on one of my plants as well that is in s/h and I have been spraying Physan 20 on it and it still isn't helping so I have pulled the plant out of the orchidarium in hopes to dry it things out a little. It is hard to dry things out when the medium is always so moist, but I figured maybe a lack of humidity might help for a bit. Hopefully someone else will pitch in with some helpful recommendations, opinions, and or answers!

[Ocelaris]

I think I sort of closed off my question, not much to answer, I'm going to be trying basically what you have... drying out the orchidarium, and using Physan / Thiomyl which should be here early next week.

i'm going to probably repot everything when I get back from Thanksgiving break.

Definetly learned my lesson in cleanliness, I wasn't very careful in keeping water from one plant to another, and I think that's where my problem came. Not that the humidity tubes etc... don't make it worse, but just need to redo everything, clean it out and soak in fungicide.

[Ross]

Originally Posted by Ocelaris

I think I sort of closed off my question, not much to answer, I'm going to be trying basically what you have... drying out the orchidarium, and using Physan / Thiomyl which should be here early next week.

i'm going to probably repot everything when I get back from Thanksgiving break.

Definetly learned my lesson in cleanliness, I wasn't very careful in keeping water from one plant to another, and I think that's where my problem came. Not that the humidity tubes etc... don't make it worse, but just need to redo everything, clean it out and soak in fungicide.

Some new clues. I think the reason you didn't get a response is the unique combination of factors. Are you saying you have plants in S/H in an orchidarium tank? If so that is probably way too much moisture. While not an expert, by any means, my observations are that an orchidarium is pretty humid (hopefully ) and on top of that, you have a planting regime designed to provide constant moisture to roots of plants that don't really need high humidity for good growth. The combo sounds to me like disaster. I really hope Ray chimes in, cause he has lots of more direct observations than I do. If you're getting mold with plants in S/H I suspect the humidity is way too high and/or air movement too low.

BTW, Thiomyl is for establish rot. Physan 20 is for mold. Don't use both. That would be too much shock for the plants. I'd opt for Physan if it's surface mold. If you see damaged tissue (brown) then Thiomyl.

[Ocelaris]

Yes, humidity is 50-70% at times, currently hovering around 60%. Circulation is provided by a 120mm fan, on at all times, and a 80mm exhaust fan, and a 2" tube which brings in humidity from the bucket.

[Ross]

I just think this is way too much humidity for the species you've collected. Keep in mind I don't grow under S/H but I do run a tank with minis and do get mold on the mounts. I would think mold would be especially bad and hard to control on plants in S/H. I treat with Physan 20. Thiomyl is reserved for confirmed cases of rot.

[Ocelaris]

Yeah, I didn't realize when I started that semi-hydro was this wet. Last time ~3 years ago I had orchids (before my sister (co collector) ended up with the collection) I had the same pebbles, and it seemed it wasn't wet enough! So I may need to rethink the bottom section, leave that mainly open to house humidity and keep the semi-hydro... The Vandas and LC are loving it though (I have 4 Asocenda hybrids (not pictured), one which is in bloom currently).

Unfortunately the Vandas (Asocendas really) are getting too big for the larger section.

Would you reccomend NOT having an enclosed part and just leaving it open? Or change growing materials for these plants?

[Ross]

Why not provide more venting? Seems like the problem is not enough fresh air. I understand what you are trying to do and yes Vandas should love it if roots are bare. Other alternatives are to mount the orchids you want to grow under higher humidity. Even Phals and Paphs can be grown mounted on slabs if the plant is humid. Other wise, yeah, just provide more fresh air. Open doors a bit or mount fan thru-wall.

[Ocelaris]

Thanks, I've actually opened totally the bottom section, and am leaving the Vandas up high.

Still trying to hit that sweet spot for everybody, and I know it's quite a mix of varieties. I'm going to clean up everybody and hopefully the mold doesn't come back.

[Ray]

Liquid accumulating on the vegetation is totally unrelated to semi-hydroponics, Bill. Water simply won't climb up the plant from the medium.

It's more likely the atmosphere of the growing chamber is leading to condensation.

And... once plants are fully acclimated to semi-hydroponics, the potting medium cannot be "too wet".