I recently switched several plants from bark to a mix of lecca and rock wool. Several are starting to grow mold on both the lecca and rock wool. I am suspecting the source might be some cheap rockwool from Amazon. But strange that it is growing on an inorganic medium? I have physan 20 but the directions says to spray the plant, nothing about drenching the medium. But can I and at what strength? I also have biosafe H2O2. Can I use that as a drench? Any other suggestions for getting rid of mold? Thanks for any thoughts.
Mold on medium
- Thread starter Roots
- Start date
Help Support Slippertalk Orchid Forum:
Simpliest with what you have would be to repot - soak fresh medium in physan before potting. For a drench banrot or thiomyl might work and be reasonably priced. If I don't treat right away I usually have some persistence in the medium. It seems like some molds are easily eradicated and others not at all. I had a mold a I was chasing in potting media this year and I ended up getting several compounds and tank mixed them. That worked well but was expensive. If rot gets into the roots then it's more of problem. Heritage is available in smaller containers on amazon and that could also be effective.
Have you applied anything anything other than inorganic fertilizer?
If it's only growing on the surface I'd spray it with alcohol.
If it's only growing on the surface I'd spray it with alcohol.
It’s hard to say from a photo, but it is unlikely to be mold.
Did you wash or otherwise pretreat the LECA? During manufacturing, “binders” are added to the raw clay to get it to roll up into little balls and to retain their “green strength” during subsequent handling and firing.
Depending upon the binders used and the firing conditions, there may be inorganic salt residues retained in the pellets. If they are water soluble, they will make their way to the surface as the pellets dry, forming a fine, needle-like “fuzz” that can resemble mold.
Flood the living hell out of it whenever you water, and the residue will be washed out of the pot over the next several weeks.
Did you wash or otherwise pretreat the LECA? During manufacturing, “binders” are added to the raw clay to get it to roll up into little balls and to retain their “green strength” during subsequent handling and firing.
Depending upon the binders used and the firing conditions, there may be inorganic salt residues retained in the pellets. If they are water soluble, they will make their way to the surface as the pellets dry, forming a fine, needle-like “fuzz” that can resemble mold.
Flood the living hell out of it whenever you water, and the residue will be washed out of the pot over the next several weeks.
To me that looks more like some sort of salt creep. I would expect an homogenous coating from fungus but this creep seems to follow the water. I think Ray is correct.
If this is a a fungus then it must originate from the plant and as the plant is healthy I wouldn't be concerned about it.
If this is a a fungus then it must originate from the plant and as the plant is healthy I wouldn't be concerned about it.
That's why I asked if some kind of organic fertilizer or stimulant was applied.
These plant looks healthy, so why should mold come from a healthy plant ? Mold or in general fungus spores are omnipresent in the air ... they need three things to germinate ... moisture, the right temperature and organic substance for food e.g. dust on the surface.
Last edited:
Wow, I love all the experience and info on this forum and everyone's willingness to share. Thank you!
Yes, I have recently added urea to my watering - and I think a little too much. I am also pushing my water solution with oxygen - not certain how much actually dissolves in the water. I've also watered once with kelpak but noticed the problem before this watering.
Maybe the rock wool retains moisture long enough that it provides an ideal habitat for mold? I wonder if I should go to straight lecca for all my paphs? I know you use a unique mix for your medium and water very infrequently. I decided, in part, to grow SH because we travel a lot and it limits my ability to water frequently.
This is definitely mold. This is my only phrag and it looks healthy but when I repotted it after bringing it home I found a rotted root ball under the crown. I left for a month and when I came back it obviously had mold on the medium. I isolated it and will see if I can get rid of it with some sort of fungicide.
Ahhh, this makes sense. I have been seeing this start on a lot of my pots. As TyroneGenade says, it follows the water line. It seems to be growing thicker so I started thinking it was the same mold starting to grow. But it does look more like a salt build up. I will start flooding them like hell. 😅
Whatever you do I would not beat around the bush - waiting around gives more chance that something secondary might infect the roots.
Mycorrhizae are fungi. They live with the plant. Many fungi live commensally with plants (and also on us). To germinate some Disa you would take native soil, pour sugar water over it and then sow the seed. The plants needed the fungi. Just because it is a fungus doesn't mean it is harmful.
Urea would definitely help saprophytic fungi as it is both a nitrogen and carbon source. If you are oxygenating that a lot of that urea is turning to nitrate before you even apply it to the plants.
What is potentially very harmful to the plant is excess fertilization which can cause tissue damage and that would see ordinarily commensal fungi turning pathogenic.
Absolutely correct. The fungus is consuming something and the bi-products may be beneficial to the plant..... Or not.
That's true .... but fungus isn't fungus and mould isn't mould. There are many diffenent species of mould and only expert are able to distinguish them by using a magnifying glass or a microscope. There are helpful ones, harmless ones and aggressive ones which cause diseases by plants, animals and human beings. What also comes to my mind is ... any mould is the biggest enemy of any orchid lab. So I would be cautious.
Last edited:
I agree, some caution is needed and there are indeed obligative pathological species of fungi, but given the extent of the assumed growth, that plant would have be dead already if this was a pathological fungi. The critical issue here is the general care of the plant: it is getting more fertilizer than it can use and that is going to weaken the plant and provide opportunities for infection by bacteria and fungi. A fungicide isn't going to solve the underlying issue which is the real threat.
Roots said that roots were rotted prior to repotting so that is likely the source. I would suggest repotting and cutting off all rotted or older roots and treating with fungicide.
Thank you. I treated last night but I think you are correct, I should repot as well. Above, when you say the mold can get into the roots do you mean to become systemic within the plant and kill it? Or it it grows into the potting medium between the roots it becomes more difficult to eradicate? Thank you for the info and the warnings. 😊
Ugh, my chemistry is so non-existent. If you have the time 2 questions here. 1. Are you saying that the fungus is able to break down the urea? With or without urease? 2. Is there a reaction with oxygen that breaks apart the urea molecule?
Yes, I don't think the plant was healthy when it came to me about six weeks ago but I think I went from under fertilizing to over fertilizing and allowed the mold a foothold. So much to learn - like how to post my responses in one reply 😂 Thank you for all the thoughts and info.
So with the mold I had my own issues with, which was similar in appearance to yours, I repotted and treated but on some of the worse cases it just came right back so something must have been in roots. Definitely not the classic snow mold that dries out the potting mix but doesn’t harm the plant otherwise. I think some secondary infections then get in through the roots and can kill the plant. I lost one that I thought I’d cured - no more mold but the plant stopped growing and rotted from the center with what looked like erwinia - orange on the leaf. The roots of that plant had orange rot inside when I took it apart once I realized it was done. I think I have successfully rehabbed the worst infected plants but I had to remove a lot of roots and some of the base of the plants. Here’s a picture where you can see the orange infected color from the roots. Thankfully I did not have many I had to do this surgery on, but the ones that survived seemed to have a scar of a sort and sealed of the infection at the base of the plant, growing new roots from the good tissue above. I can’t speak to biology of exactly What is going on
Attachments
Similar threads
