When when is it too early to use preventative fungicide on seedlings?

[Greenpassion]

Well once again I'm attempting to open up my Grow rooms. For those who joined the topic the last time I started one if you remember I had to destroy all the plants, break the room down and clean everything as best I could because everything was destroyed by powdery mildew So three weeks ago give or take I started 5 Auto seeds. They're doing fine in their gallon forever home, but I want to start using green cure as a preventative from this powdery mildew. My understanding of powdery mildew is that once you can see the white on their leaves they've already had the powdery mildew for 2 weeks. So this time around, I want to do preventive maintenance and see if that makes a difference. But are they too young? Any advice?

[Canuck147]

Good idea - I would - did actually. My girls were at 6 nodes - topped all 3 - decided to spray to prevent WPM. Alas - my spray was a little too strong and I didn't wait until they were totally dry before putting them back into the tent. Next day got the beginning of a few yellow/clawing leaves and I had thought I stunted them. They all came back around but I definitely stunted 1 - she's in full bloom at 10 inches tal. The other 2 are doing like they should.

Side note - used to use a red bloom light which i was convinced contributed to my mold problems. Don't use it anymore- but on my current light I have bloom lights which I have keep off the past 3 weeks cuz I have 3 more seedlings which I know from past grows that the seedlings don't like the bloom on. No WPM happening at the moment and I'm going to keep the bloom lights off for now. Let the 4 COBS do their thing.

I also use chlorox wipes on the inside of my tent once a week.

Most of the leaves I sprayed have since been cut off and am debating whether to spray again - or wait.

[SoOrbudgal]

Yes i use chlorox wipes also after every harvest. Interesting theory on the red spectrum Canuck147. I've been lucky not to have a contaminated grow spaces that had the effects on plants like you and others. Sorry Greenpassion i've not had that issue as bad so never used it.

[Greenpassion]

Canuck147, thank you for that. Are you talking about autos? Just to be sure? My babies are only about an inch and a half tall with the first set of leaves, and the next ones just beginning. I use viparspectra 450 watt each. I never thought of keeping the bloom lights off, but I will try that along with maybe spraying a watered down mix of Serenade...? Or hydrogen peroxide? I'm really concerned that the PM will come back. It was devastating for me to have had to destroy a total of 14 plants, and to tear down 2+ years of work 😢

[Canuck147]

Autoflowers is all I grow - seedlings are too young in my opinion to spray. I use a concentrate for spray - made ny Safer's called Defender Garden Fungicide.

[Greenpassion]

Got it! 👍Thank you. I'll look for that.