How often do you apply physan20?

[RoseSD]

I have fungi growing in a few of my sun loving orchid pots so I treated them with 1tsb per gallon of physan20. I soaked the whole pot for 10 minutes each.
I know a nursery owner who uses physan20 regularly to "prevent" problems in his orchids. is anyone here also using it to prevent issues? How often do you apply the solution? Is there a risk of resistance developing?

[Dimples]

Using chemicals (natural or synthetic) as a preventative is the best way to encourage the development of resistance. Prevention should be through cultural means. Treat when treatment is warranted.

Exceptions include things like copper fungicide that is intended to be used preventatively but only when conditions warrant it’s use.

[RoseSD]

You are so right. It is just like the abuse of antibiotics in humans.
My guess is that nurseries and orchid business owners rather not risk losing their orchids to infections.

[Roberta]

I hardly ever use Physan except to control algae in the birdbath... (harmless to birds... would be toxic to fish there are no fish present), or on the floor of the greenhouse (which can get slippery and sticks to my shoes making a mess in the house). But that's it... And I have never had a fungus problem. Might get an occasional mushroom in a particularly wet pot, but harmless. If you have a fungus problem, best to examine your cultural techniques and look for ways to improve them so that you don't encourage pathogens. For a start, improve air movement - get a fan, or grow outside.

If I have a plant with a rot issue on roots, I rinse them well with water, pot with fresh medium so that there is air exchange, when I water I do it so that the pot is flushed which washes out the crud and pulls air into the root zone. In about 30 years of orchid growing I can't recall a time when I needed a treatment for my plants beyond "clean it up and improve aeration". No Physan!

In some climates there can be chronic problems with insects or pathogens. But in San Diego, you have a very benign climate that should not require any routine "treatments".

[Ray]

Originally Posted by RoseSD

I have fungi growing in a few of my sun loving orchid pots

Fungi or algae?

[RoseSD]

Originally Posted by Ray

Fungi or algae?

Fungi
I know why it happened. I shouldn't have reused the moist moss that came with the orchids.

[Roberta]

Originally Posted by RoseSD

Fungi
I know why it happened. I shouldn't have reused the moist moss that came with the orchids.

Solution to the problem isn't chemicals, it's a repot with fresh medium after a good rinse with water. With fresh air, the plant will take care of the problem.

[Ray]

In my opinion, Physan usage should be limited to disinfecting the growing areas and structures, benches, and tools. It’s use on plants is limited to topical treatment, while most infections are systemic.