White powder mildew and Physan

Thread starter #1
Sorry if this has been covered, I couldn't dig up anything relevant in search.

Is it ok to use Physan 20 to control white powder mildew? The Physan info shows 2 tsp/gallon for control of mildew on roses.

I had some buds develop the mildew during the drying process. Despite some claims otherwise (wash with hydrogen peroxide :hmmmm: ), conventional wisdom seems to say throw the buds away. Apparently smoking such buds is not a big problem for most, catastrophe for some.

If it's not a problem using Physan, how? Just for growth stage, never for buds?
Thanks, I understand that. I'm asking about using Physan as a preventative measure, I'd really like to avoid the problem in the future.
Sorry about the misunderstanding. Like JoeDaddy, I would suggest lowering your humidity and getting buds really dry before curing. Also increasing air circulation. "An ounce of prevention..."

As broad spctrum cidal agents go, Physan doesn't look too awful, but what I'm reading says it's NOT INTENDED FOR USE IN GREENHOUSES WHERE FOOD CROPS ARE GROWN--i.e. not only should you not apply it to the plant, you shouldn't even use it in the grow area.

Here's the safety info: Physan MSDS

I sympathize, but it looks like the best bet is a good soap-and-water scrub down, good sanitary practices, and temperature, humidity, and air flow control. That should be enough!
Thread starter #6
Guess I'm surprised Physan20, a local grow shop swore by it over twenty years ago.

Maybe the best way to disinfect grow environments and equipment. Mix a correct dilution, put it in a spray bottle, go to town.
It includes instructions for treating plants.

It's very powerful, my questions are about treating plants that are consumed -- smoked, vaped, eaten, whatever.
Thread starter #7
Sorry about the misunderstanding. Like JoeDaddy, I would suggest lowering your humidity and getting buds really dry before curing. Also increasing air circulation. "An ounce of prevention..."
We were typing at the same time.:high-five:

I've only got so much control over heat and humidity. Harvest was hung in a tent --fan running and good exhaust -- for almost two weeks. I hadn't bothered looking close enough, about a quarter developed the white powder mildew.

I've used the Physan20 for general disinfecting over many years with no adverse effects I can tell. They make a point to warn of dangers when applying P20, don't get it on you, not in the eyes, don't breath it. I get the impression -- I may be wrong -- those dangers dissipate after use.
no adverse effects I can tell.
With respect, and not to be argumentative, but "no adverse effects that I can tell" is a very low bar for safety. This is a substance used to poison algae and fungus. My advice--and the advice from the people who sell it--is not to use it with a food crop (which would include cannabis). If it's just for personal use and you're willing to take the risk, that's one thing, but if you're sharing it with or selling it to others, you owe it to them to tell them that you've treated it with a fungicide/algicide. Others are producing high quality buds without resorting to toxic chemicals, and you can too. It just takes a little more work and possibly cash outlay for climate control.

And by the way, this doesn't look to me like a substance that is going to "dissipate"--when you lay it down, it's going to stay there.

Sorry, I don't mean to lecture, but you did ask and I do have some background in this area, and the physician's rule of "First, do no harm" comes to mind here.

Happy growing!
Thread starter #9
I'll keep your advice in mind, Scientific. As I noted, I'm surprised not to get more response on this thread. Maybe that shows that concerns about P20 are more common knowledge than I'm aware.
Thread starter #11
You also can try posting a thread with this question in the pests and disease threads for Q & A
I'll do that. Not to beat a dead horse, this from the Physan20 website --

Physan 20 as a Foliar Spray for Pathogen Control

Physan 20 can be applied to plants as a foliar spray to control pathogens. However, it is NOT an insecticide and will not kill aphids, mites, scale, or pests of this sort. Physan 20 leaves no harmful residue if foliage is dried and smoked.

Hydroponics - Physan
Well there it is, right from the source. Cool.

Me, I don't want to ingest alkyl dimthyl benzyl ammonium chloride, though. I think creating a growing environment in which fungicide is not required is by far the best way to go. Humidity control!