Do I need Physan 20?

[hanka]

In was packaging 16oz. 128 oz Physan 20 Gallon costs about US $35

[orchidsal]

Yes it is used by some people as a preventive fungicide and the instructions that come along with the bottle even suggest once a month preventive applications. It may not cure every disease or fungus that strike your orchids, but it can be a big help with some pathogens and it is excellant in stopping the transmission of these organism's from one plant to the next. AL

[raybark]

I used to be a regular Physan user in my greenhouse to keep algae down and in my RO tank as a general disinfectant to hopefully keep rots at bay.

Unfortunately, some plants are more sensitive to it than others, and I'm convinced it led to the decline of some (don't ask which, as it has been a long time since I quit).

Then I "discovered" my low-dose fertilizing technique and - Lo and Behold! - my algae problems went away, so I stopped the Physan use.

Needless to say, with my current regimen that includes Inocucor, rots are not an issue either.

[CattyRobb]

As you know my collection is not large. So far, I've only had an issue with one plant that I'm aware of. It was Epicattleya Tropical Jewel 'Hihimanu'. The plant was half Epi. stamfordianum and the leaves were a bit more tender than most of my other plants. I'm not absolutely sure it was the Physan that caused the problem though. Could have also been all the misting I was doing at that time. (I don't mist foliage any more, it was a brief foray) The plant did have problems from the beginning, hence the Physan. If I ever decided to try these newfangled biological products, I'd give the Physan use up, at least in any plant pots. Guessing it's not a good combo.

[raybark]

If I ever decided to try these newfangled biological products, I'd give the Physan use up, at least in any plant pots. Guessing it's not a good combo.

True enough. The Physan (or any disinfectant, for that matter) will kill the "good bugs."

[Monks-in-Miami]

I've noticed that the rain water collected in my barrel is sometimes green. Not sure if this green -- which I assume is due to algae -- affects the plants in anyway when I water them. Should/can I add some physan just to keep the algae down?

[raybark]

I've noticed that the rain water collected in my barrel is sometimes green. Not sure if this green -- which I assume is due to algae -- affects the plants in anyway when I water them. Should/can I add some physan just to keep the algae down?

Algae, per se, does not affect your plants. One might argue that dying organic matter within the potting medium is bad, but frankly, I doubt that there's enough to be of any consequence. I used to add Physan to my RO tank for that purpose, but some plants (notably dendrobiums and thin-leaved plants like coelogyne, for example) don't like it.

If you can fins a way to block the light getting to the barrel contents, that'll take care of it.