Pool Algaecide for orchids

danesnpits(2a)December 23, 2013

Hi there, I was about to purchase physan, and then heard about this pool algaecide stuff. I have seen different strengths from 20% down to 5%. Does anyone have a formula to use for the different strengths for tsp/gallon?

I would also love to hear your thoughts on using this product, and how you use it in your orchid growing. Any info would be truly appreciated.

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Why do you need algaecide?

    Bookmark   December 23, 2013 at 1:38PM
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It's the alternative to physan 20

    Bookmark   December 23, 2013 at 2:25PM
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Ah but that wasn't the question. Why do you need it? You are asking about people's use but don't explain what your intended use is. What problem are you having that you think you need a physan-like product?

    Bookmark   December 23, 2013 at 7:24PM
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Hi terpguy! Thanks for asking, and sorry I wasn't clear earlier. I got a shipment of orchids, 27 of them, from catts, to masdevallia, pansey orchids, oncidium. just to name a few, from a breeder in british columbia. They arrived frozen. I am in Saskatchewan and even with the heat pack, it was -45 Celsius here when they arrived. UGH!!! They are a mess and I am trying to save them. Leaves are dropping off, discoloring, black rot looking things by crowns, roots in some look terrible. Plus I am a smoker! And I did not wear gloves touching them. I did not know! So I figured perhaps I should try and treat them for fungus/bacteria/rot. I just can't not do anything, I need to try and save as many as I can. The seller is going to be mailing me a new shipment when it warms up regardless..but these orchids are living beings, I gotta try try try!

This post was edited by danesnpits on Tue, Dec 24, 13 at 6:25

    Bookmark   December 24, 2013 at 6:22AM
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I wouldn't worry about a fungicide or the fact that you smoke. Neither will help/hurt them at this point. They may be too far gone but there are a few things you can try.

First off, warm them up. Put them in a warm room, do not water them, cut off any black, mushy parts and wait! Give them good light and if possible try to supplement with additional lights. Do not water them at all. Let them dry out.

I had something similar happen years ago and a few pulled through (Catts). The Oncids rotted away as did the Phals. But the Catts sent up new growths a few months later.


    Bookmark   December 25, 2013 at 1:21AM
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Thanks for the response Jane. These plants have already been in my home for 2 weeks. So there are now signs of bacterial infections. dropping leaves pseuobulb rot, root rot, the whole 9 yards. I have already dosed them with hydrogen peroxide as that is all I have.

I wish someone would answer my original question though regarding the pool algaecide..if not for use now, for future reference. I have the file where I found it from an orchid board regarind using the pool stuff in place of physan 20. I am in Canada, and getting physan is just out of my means. Please, anyone?

    Bookmark   December 26, 2013 at 12:04AM
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arthurm(Sydney, NSW AUST)

I think you are seeking some sort of wonder treatment when all you can do when faced with such a disaster is put the plants in good growing conditions, trim off the dead bits and hope for the best.
I've got a thousand orchids and have never used Physan on any of them.

    Bookmark   December 26, 2013 at 2:56AM
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Thanks arthurm, yes it is what I am doing, taking off dead, doing what I can, under the circumstances. They are under grow lights right now, 400 W metal hallides, plus a couple are under just a regular 6500k light bulb. I have 2 humidifiers going right now as well. When I walk in the room it feels like alot of humdity is in there. Perhaps there shouldn't be any?

I would still please like to know the answer to my original question of using pool algaecide and how to use it. If I decide to use it down the road, I will have the knowledge. Knowledge is key. Please someone, I am really wanting some answers.

    Bookmark   December 26, 2013 at 10:49AM
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I would not run the humidifiers and would dry the plants out. The odds are that you might be able to save some of the roots and maybe a bulb or two. I would not keep them damp.

I know I've read where pool algaecide could be used but would not know the %. Don't worry about that now. Just see if you can save whats left of the plants.

As I wrote, I had some success by letting the plants go totally dry after all the rot was removed and the plant stopped losing leaves and bulbs, I left them and waited to see if any new growth was produced which did on a few. The rest died.

There's only so much you can do. Stop watering and humidifying. Just keep cutting off any rotted tissue until you reach healthy. You could dab some cinnamon or alcohol on the cut parts.


    Bookmark   December 26, 2013 at 11:50AM
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Argh, more confusion! I thought Physan 20 was often mentioned in this forum as a treatment for fungal problems. I've been using it about every 2 weeks. Am I misremembering?

    Bookmark   December 26, 2013 at 4:20PM
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Thank you Jane will follow your suggestions. My orchid grower will be sending me new ones when the weather gets a bit better. UGH..the last shipment arrived at -46 celsius. The heat pack was cold as ice.

vtandra, yes you are correct. Physan 20 is what I read to be used as either fungal issues/bacterial and as a preventative measure at 2-4 week intervals. The pool algaecide was mentioned as a cheaper and just as effective alternative. I should post the link if I can find it to where I read some info regarding the pool stuff.

Here is a link that might be useful: Fungicides and Bacterides plus alternatives

    Bookmark   December 26, 2013 at 4:35PM
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James AKA lumpy_j

I would think different manufacturers use different ingredients. I would find out what chemicals are in the algaecide you want to use and look them up to see if they can be used on plants. It would be easier to pick up something at the garden center. Most people say stuff made for use on roses will work for orchids.
As for your plants, you may just be seeing the results of cold damage and not have an infection at all. As Jane said, I would keep them warm and dry for a while.

    Bookmark   December 26, 2013 at 6:00PM
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Ok, I'm back. Bear with me, lots to say so this will be long.


The reason you aren't getting any answers on the algaecide use is because nobody here uses it. It is algaecide, not fungicide. Physan can be used to remove algae from greenhouse glass, or disinfect a table top, but thats about it. No real application to the plants themselves.

Forget it...

Most bactericides are harsh chemicals. As such, you'll be hardpressed to find one that doesn't require a pesticide applicators license AND be used only in a commercial greenhouse. Theres just not much at all out there for use in home. I like how the link says that Daconil can be used for bacteria, but the label clearly says fungicide. Based on that alone your link is suspect. If you see something that says its for bacteria, is labeled for indoor use, is available at a garden center or big box store, be skeptical.

Specifically on your shipment:

You've gotten great advice here. But forget this talk of bacteria. At -45C, Lumpy is correct that you are dealing with freezing damage, which looks like bacterial rot but is not the same.

As both Jane and Arthur wisely noted, the only thing you can do is give them good culture and hope for the best. Whatever happens to the plants is what is going to happen; theres not much you can do at this point.

I'm incline to agree with keeping them on the dry side at the roots. However, I would strongly recommend you DO run the humidifier. Heres why:

First, humidity at the leaves is actually very healthy and theraputic; rootless orchids are more likely to survive if they have high humidity because it helps reduce/surpress the big stress of evapotransporation (increase evapotransporation = dessicated leaves). Keeping the leaves as plump as possible allows energy to be put to root production. As long as the plants aren't in a stagnant box, humidity will only help, not hurt.

The sphag-n-bag trick for helping rootless orchids is there for a reason. The principle is sound but the lack of air circulation in the bags is a major issue.

Secondly, and more importantly, you are dealing with a lot of cloud forest species (Masdevallias, Odontoglossum & miltoniopsis hybrids, etc), all of which require wet conditions, cool temperatures, and high humidity. Keep them dry and watch them decline quickly from being even more stress. Only heat can kill them faster.

We've all been here many times, and all have different ways of dealing with it. I grow my orchids outside like a lot of indoor growers. But I often keep my plants out to down into the 30'sF (VTAndrea, I can commiserate. On here I was once led to believe the same thing. Physan is not your traditional fungicide. It is more like a surface disinfectant (think Lysol) that also works wonders for algae. The problem is that it is highly toxic to fish. So I don't use it. Not that I really have need for this kind of product anyways.

    Bookmark   December 26, 2013 at 9:02PM
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I want to respond to Terpguys information which is very good except his statement about humidity.

I froze a number of orchids, mostly Catts about 10 yrs ago. They were frozen solid. They were left in front of an open window for 2 days while the temps dropped to 2F.

This is what occurs. Every leaf is lost. Pbulbs get soft circular areas which quickly become mush as the bulb rots. The cells are destroyed by the freeze and the only hope is to save as much of the bulbs and roots as possible.

I cut chunks of dead and dying tissue out of the bulbs and used alcohol to, hopefully stop it from turning bacterial. It is not bacterial at the thaw-out stage. But will become so quickly.

My reasoning for stating that high humidity is wrong is because you need the rotting tissue to dry out. As the leaves are lost, humidifiers can only create more problems. Been there, done that!

Most of my plants died. A few slowly recovered and I got new growths in spring.

The main thrust must be to stop the rotting tissue from destroying the rest of the bulb. If his plants were truly frozen, the leaves are lost. They are the thinnest part of the plant and fall off quickly. If the Masdes and Oncids were frozen, I doubt any will survive. The Catts stand the best chance because they have a thicker root system and bulb. But the bulbs are full of liquid and high humidity will make matters worse.

I stand by my advice to put the plants in a warm, dry environment.

Good luck,

    Bookmark   December 26, 2013 at 10:00PM
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Wow you guys I am overwhelmed here by the love and care you guys have for orchids, and especially my situation. Jane and Terpguy, u both have given such amazing advice. Because of terps post, I won't worry anymore about even trying to learn about the pool stuff. And Jane, great post regarding what happened to you. I can see no humidifiers being key to keeping rot down for sure. It makes alot of sense. But on the other hand, now that most of the leaves have already fallen off, and all the yucky stuff removed by me (it's been a couple weeks now they have been in my home), I have decided to keep the humdity high for now and hope for the best. I do have other living orchids in good shape that will benefit from it, and I will be getting a replacement shipment with everything I did lose. So whatever lives and dies, will be ok. I will try my hardest to save what I can. Again, thank you all so very very much. I feel so much better about this situation.

    Bookmark   December 26, 2013 at 10:55PM
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Jane, plant physiology 101: is the mushy part mechanical/physiological damage or pathological in nature? Hint, its physiological.

Your response suggests incorrectly that the mechanical/physiological damage can proactively spread and kill the plant.

The truth is the reverse: the damage has already been done. The mushy is the manifestation of that damage. If the plant is going to die, its because the damage has already been done. Humidity will have no effect on that outcome.

I'm sorry, but the science (and to be frank, norms of horticulture practice) does not support you in this.

Just as the Masdies.

Danepits, you are obviously free to do what you want and take what you will from this debate, particularly since you don't know the background of the people you are getting advice from. I strongly recommend you research the plants you have to make sure its the right approach.

I certainly wish you the best of luck. We've all been there, it sucks. You just have to learn from this and grow in your passion. Biggest lesson: Don't order plants during the winter :)

This post was edited by terpguy on Thu, Dec 26, 13 at 23:11

    Bookmark   December 26, 2013 at 11:09PM
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I agree with most of the advice already listed, especially, not mail ordering plants during dead of winter. ( Go to a local show if you must have a plant and personally carry it home in a warm car : -)

Note on Physan:
Glen Decker of Piping Rock Orchids gave our orchid society a nice talk at a recent meeting. He says he would rather use "non-toxic to humans treatments" on his plants if any is necessary. He recommends using a full strength spray of listerine on plants with fungal issues. He said only use the heavy duty stuff if the situation is drastic.
He also advocates using a soap spray or any of the homemade alcohol-soap and similar solutions, such as ground cinnamon. He says that he would rather not expose himself, his family and workers to potentially harmful chems. I concur, and since my tiny greenhouse is attached to my kitchen, I don't use any heavy duty chems in there. Neem is also a good treatment for fungal issues and is non-toxic to humans, pets and non-pest insects.

(Just to be fair, I'll state that Glen vends at our February show and gives talks, so he's a club favorite. I've bought from him, as well. )

Certainly an algaecide formulated for pools does not sound like a good choice. If you use an improper dilution you risk burning the plant, and/or not eliminating the disease. On chemical treatments, there is usually a note on the label that warns you not to use it for purposes not listed on the label.

Good luck and I hope you find a safe solution soon...certainly patience is one of the ingredients!

Happy New Year
ML in chilly WMass

    Bookmark   December 27, 2013 at 9:48AM
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shavedmonkey (Harvey in South Fl.)Z10b

In south Florida, algae is an issue. Currently, if I look closely I can find algae in my yard. It would be everywhere if I did not make an effort to keep it away. According to Dr. Motes in South Florida he sees benefit for the use of algaecides. He suggests using one or two teaspoons of home depot brand pool time per gallon. http://staugorchidsociety.org/PDF/Motes-Sep.pdf is a link for Motes.

    Bookmark   December 27, 2013 at 2:58PM
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Big sigh. Full strength Listerine? Anyone disagree with this?

    Bookmark   December 27, 2013 at 9:06PM
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Listerine can't hurt. I know people who have used it in the past. Not sure how effective it was but it didn't hurt the plants.

Never knew that SM. Interesting.

    Bookmark   December 27, 2013 at 11:00PM
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I've used the listerine trick myself, and it does seem to control pests such as scale and also limits the black spotting on Oncidiums and Zygos. It must be the alcohol and thymol which are the active ingredients. Like mixing isopropyl alcohol with a soap mixture.
Then again, I've also used the soap and alcohol and Neem. But we've veered away from the specific algae question. I don't have algae problems, so - Very sorry for the diversion. Massachusetts has different cultural problems from Florida and Canada.

Happy New Growing Year to All

    Bookmark   December 28, 2013 at 8:48AM
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Thanks everyone for turning this thread into such an educational one for thisvery newbie orchid enthusiast. I have heard of the listerine treatment but never tried. Im staying away from the pool stuff cuz of this thread. Wonderful talk everyone! My frozen orchids and I thank you all. I will update this thread as I go along and will let you know what I have managed to save. I have taken photos of the damage so hope to get some nice after photos of hopefully new growth in some. Will post!

    Bookmark   December 28, 2013 at 12:00PM
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Best of luck to you!

    Bookmark   December 28, 2013 at 1:36PM
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