Powdery mildew started to show on a few leaves. Luckily I spotted it early. It was mostly on a few fan leaves and 4 hours earlier it wasn’t there. It was on the Tropicana Cookies only as far as I could tell.
Here is this weeks video taken on day 28.
Powdery Mildew Sucks! What I Did To Fight It
Powdery mildew is everywhere. In my neck of the woods, which is Western Washington, the humidity can be fairly high. Usually it is low enough when the sun is out that it is not an issue. But we have had several days of cloudy weather with high enough humidity and the right temperature for it to flourish. Mid sixties and 50%+ humidity are optimum for it.
Everyone says prevention is better than cure but that is not always possible so I needed a plan of action to fight and get rid of powdery mildew on my cannabis plants.
My closet stays in the lower to mid 40% humidity range which is normally low enough to keep it from gaining a foothold. Because my house isn’t heated at this time of year humidity can be mid fifties inside. My air intake comes from there so with spores everywhere it is really no surprise some got pulled in.
What I did was add another fan to improve air circulation. Because space is tight in my grow closet I like to use tower fans. They are upright and move a tall and wide swath of air. They give me good air movement without beating my plants up.
Here is what I use:
I have had one of these for 3 years now and it still works fine so I did not hesitate to buy another.
Besides adding the fan I also did another leaf strip. I removed the few infected leaves I had and a bunch more to help get air flow through the canopy. I also wanted to get more light to the lower branches on the first screen. I was a bit hesitant to defoliate on day 28 because I was not sure how much, if any, regrowth there would be. Usually I do this by day 21 while plants are still stretching.
I sprayed the leaves with water and a bit of peroxide. Some say this works and some say it doesn’t. Actually just plain water can remove it from the leaves. PM likes moisture but not wet. Other people swear by spraying a 10:1 mixture of milk on your plants. The idea of milk spoiling on my buds definitely did not appeal to me.
I have used in veg as a preventative and it seems to work but it can burn leaves and leaves a residue so that was not an option at this time even though I know people do it.
What I decided to do was order a product called Serenade that is a natural fungicide.
It is certified organic and contains a special strain of bacteria that attacks mildew and other plant diseases. I have heard you can use it right up to harvest but I certainly hope I wont have to.
I will test it out and see if it works, probably on my veg plants first to see if it burns or leaves a residue. I am hoping I wont need to use it at all in flower but I will have it just in case.