Wetting Agents, Bad or OK

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myxodex

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I sometimes use a non-ionic wetting agent/detergent with my feed (Growth Tech). I add just enough to give a "short lived" foam to the final mix when I shake it up. I've noticed that with some pots the watering runs through the medium leaving areas unwet even if I flood the top with enough to wet the whole pot. Years ago I used a powdered feed that had some wetting agent incorporated that produced quite a persistant head of foam when shook up; this mix was less prone to leaving dry spots.
I'm reticent to increase the concentration of detergent in my mix even though I'm using quite a bit less than the recommended amount, perhaps I'm being over cautious ?

There isn't a huge amount published about the effect of wetting agents on plant growth, but the little there is shows that detergents can be detrimental above an upper limit, but beneficial when below this limit, and of course some plants are more sensitive than others. As none of the above was done with orchids, I'm wondering whether any of you have any experiences or thoughts on this.

One thing that does stick in my mind on this issue. Many years ago as an undergraduate in a plant pathology course we had to deliberately infect plants with fungal or bacterial pathogens. We always added some Tween-20 detergent to the inoculum as it significantly increases infection rates. Tween 20 (aka polysorbate 20) is one of the less toxic detergents, it is biodegradeable and inexpensive. I suspect that the wetting agent that I'm using from (Growth Tech) might actually be Tween 20 although I cannot be sure.
 
As far as I am aware, the only issue with wetting agents is that your organic potting media components will decompose more quickly.
 
I was under the impression that most commercial fertilizers (at least the bigger ones - Miracle Gro, Scott's, etc) already had wetting agents added to them. A lot of people use those regularly on their plants with no adverse effects. So I wouldn't imagine adding a wetting agent (at the recommended dosage) to a fertilizer that does not already contain one would not hurt your plants.

Interesting point about wetting agents possibly making plants more susceptible to pathogens. I guess that makes sense, but I have never really thought about it. Hopefully the boost in nutrition would lead to more vigorous growth that would counteract increased susceptibility?
 
Wetting agents do not make the plants more susceptible to pathogens.

In the example stated, they were added to increase the wetted surface area, thereby putting more pathogens in contact with the plant, increasing the likelihood of infection.
 
Wetting agents do not make the plants more susceptible to pathogens.

In the example stated, they were added to increase the wetted surface area, thereby putting more pathogens in contact with the plant, increasing the likelihood of infection.

Just curious - has anyone actually looked at that? I understand that surfactants are going to increase the wetted surface area; but, at the same time, they are also going to also have an negative impact on the waxy coating (i.e. breaking down/permeabilizing) the plant uses as a barrier against pathogens (how much of an impact, I do not know). This may also contribute to higher probability of infection.
 
''Just curious - has anyone actually looked at that? '''

Yes they have. Excessive use of wetting agents can contribute to increased root rot. I suggest half strength and not very often. Be careful with valuable plants.
I don't use it on Paphs but sometimes on Catts. If you water well 3 days in a row you should be able to properly wet the media.
 
Just curious - has anyone actually looked at that? I understand that surfactants are going to increase the wetted surface area; but, at the same time, they are also going to also have an negative impact on the waxy coating (i.e. breaking down/permeabilizing) the plant uses as a barrier against pathogens (how much of an impact, I do not know). This may also contribute to higher probability of infection.
What makes you think that a wetting agent chemically affects the cutex?
 

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