Use of fungicides, bactericides, soaps and compounds.

[Cdmcmonigle]

Has anyone heard of chlorhexidine for horticultural purposes? I was wanting to try it as a soap for my orchids. Also, I have used physan 20 recently on my plants, I bought thiomyl and dacinil to prevent resistance buildup. I am looking for any advice on using ANY fungicide or if anyone has used beneficial bacteria in their root zones with success. I grow mainly in a coco chip/LECA mix, some have sphag thrown in, a few phals are growing well in full water culture, and nine of them are in a hydroponic setup. I have two zygo's that a are currently in seclusion from fear that they havea fungus. Two cattleyas might also have a fungus. Any words of wisdom, what has or has not worked for you, regimes, preventitive strategies...

[Orchid Whisperer]

On another forum, there was an exchange between a grower that found bacterial innoculants useless, and another person that promoted their use. Both posters had science or engineering backgrounds.

I have no "skin in the game" but any bacterial innoculant product should list the bacteria they add, why they added it (this might be in reply to an inquiry from you to them), and should be able to say why it is or is not good for the type of plant grown (again - reply to inquiry). Also, bacteria are typically anaerobic or aerobic (or facultative, meaning they can operate both ways). A bacteria claimed as beneficial is only beneficial if it can live in the root zone of your plant (applying a beneficial anaerobic bacteria to a mounted orchid is probably not going to help you much). Any claim about "proprietary" or "secret" bacterial blends would make me walk away.

I'm sure beneficial microbe products are useful in some situations, useless in others. Do some due diligence to see if a product will benefit your growing situation, or not.

[dounoharm]

good reasoning whisperer....one thing I might add: when asking for advise on products and problems, it really helps if the poster puts some generalization of their location and growing conditions.....some products are not good for indoor use or around children and pets.....you don't want to save an orchid and lose your dog or cat...or child....

[Ray]

I think that what many fail to understand is that it isn't the microorganisms themselves that have the effect upon the plants, it is their exudates/secretions - call them what you will.

There are whole categories of such products that don't contain live bacterial or fungi at all, and it is getting to be more and more frequent that on-site fermenters are employed, so that the fermentation product may be applied to the crops.

That, may very well be the reason that only one or two species are listed as being present, while the fermentation process employs many more. And since it is the specific fermentation byproducts that are key to the performance, keeping those private is smart.

The converse of your "walk away" argument would be that you'd happily buy a product with many ingredients listed, but if you look at products being marketed to the cannabis grower, you will see very detailed delineation of the zillions of ingredients, but there is absolutely no evidence that they actually do anything, outside of lining the producer's wallet.

I try to be more pragmatic - if I give something a reasonable trial and it works, I'll probably use it. The "scientist and engineer" in me might be frustrated at not knowing what's in it, but so what?

[Ray]

I will add that the same is true of so-called mycorrhizae products - many have one or two species listed, others have many, but none have shown any evidence of being effective on orchids.

Buying one of those while walking away from others based upon the label contents is folly.

[Leafmite]

I have never used any fungicides indoors, just the Captan (with copper) for the fruit trees. Captan is not a product to be used indoors and one should always wear the suggested protective gear.

I agree that it helps to know more about your growing conditions so we can help you tweak your environment.

Someone in our OS grows nearly all of her orchids in full hydroponics with amazing success so it can be done.

It is best to try to prevent fungus issues. If you are not using a fan, I would advise adding one. I use simple rotating fan which helps to dry everything. Keeping the leaves dry or giving them a chance to dry before nightfall helps. Certain conditions can stress a plant and harm their ability to resist infections. Adding a Calcium supplement seems to help create stronger new growth that resists fungus infections.

[estación seca]

Some fungi respond to some fungicides, and not others. It's not a good idea to treat unless you know what you're treating. If you treat with an ineffective fungicide you risk inducing resistance in other potential pathogens, and you kill beneficial organisms that inhibit pathogens.

In general, prophylactic treatment of plants or animals for microbial pests is a bad idea, unless known pests are a known threat and known effective treatments are available.

Some bacteriologists predicted widespread introduction of antibacterials into hand soap in the 1980s, initially done by soap makers to profit off fear of HIV, would lead to outbreaks of resistant bacterial infection. The US CDC pooh-poohed this until recently, and recommended antibacterial hand soaps for years. Harmless bacteria on human skin are known to inhibit growth of pathogenic MRSA bacteria; these harmless bacteria are much easier to kill with antiseptics. The CDC now recommends hand soaps for the general public not contain antiseptics. People who treat plants or animals indiscriminately with antifungals or antibacterials, thinking "it can't hurt and it might help," are wrong on both counts. The current MRSA epidemic around the world was likely promoted by antibacterial hand soaps.

Improving growing conditions is more important than chemical control. Healthy plants grown in strong light at correct temperatures are quite resistant to fungal infection. Good air circulation is also important, to keep spores from settling on plants.

I don't know anything about chlorhexidine on plants. It is a potent and persistent bactericide on mammalian skin, and is the preferred antiseptic skin prep solution for surgery not on the head and neck. It is also used as a hand wash soap for surgeons and hospital staff. It causes corneal damage in the eye, and deafness if instilled into the ear. It causes nerve toxicity if placed on nerves, or if swallowed. I would never spray chlorhexidene due to the risk of getting it into the eyes or ears.

There are very weak chlorhexidine oral rinses used for human and animals, to prevent gum diseases. These are rinses only and should not be swallowed.

[orchidsarefun]

Agree.
It's best to correct the problem/s with your growing conditions. I know fans are generally recommended but I've never used one and don't have fungal issues.
Also take a look at cinnamon ( in a paste), hydrogen peroxide and rubbing alcohol as more 'friendly' solutions to everyone indoors. I occasionally use Neem oil as a general spray and that has anti-fungal properties.
I remember using physan20 once - that caused an explosion of fungal problems as it upset the fungal ecobalance. I had creepy yellow mushrooms/ toadstools suddenly pop up, amongst others and I had a couple of WTF moments.

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[Orchid Whisperer]

Knowing what is claimed to be in a product is at least a starting point for making an informed decision. If a product's maker is unwilling to provide that information, it suggests they are unwilling to provide the information to make such a decision. Therefore, time to walk away.

[Leafmite]

Originally Posted by orchidsarefun

Agree.
I remember using physan20 once - that caused an explosion of fungal problems as it upset the fungal ecobalance. I had creepy yellow mushrooms/ toadstools suddenly pop up, amongst others and I had a couple of WTF moments.

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Oh my!

I tend to use isopropyl alcohol indoors to dry and disinfect. It is probably not as effective as a fungicide with copper but it is much safer. I have lost a few plants to fungus issues, though, so if OP has a serious issue, OP probably needs something stronger.
My problems with fungus always have occurred in new orchids or when I lapse on the calcium.