heres what the serenade bottle says:
0.0074% QST 713 strain of Bacillus subtilis (
information here)
99.926% inert ingredients.
It controls bacterial spot, powdery mildew, rust, gray mold, leaf blight, scab.
Baking soda does not work as well as Serenade, Baking soda WILL change the pH on the surface of the plant- but Serenade does that, and introduces this Bacillus subtilis which is like having your own army of evil henchmen that attack cannabis mildew/fungal pests.
Urban Garden Supply in Woodland Hills, CA carries the product for $9.95 per bottle, and comes in a handy spray bottle... I apply to areas effected, where you can see the fuzzy mildew forming, and it immediately correct the issue on that part of the plant, and prevent it from returning.
Do not wash down your plants, water and spray plants with the mixture (either baking soda, or serenade) AS SOON AS THE LIGHTS COME ON to prevent moisture from remaining when the light goes off.
Increase air circulation in the grow, space plants further apart- add another oscillating fan to blow the plants... Walmart has one for $17.00 right now, easy to set up- and works very well and quiet.
Spray your serenade or baking soda mixture as you notice the powdery mildew
Check for powdery mildew EVERY water and feed or every 3 days.
Serenade can be used up to the day of harvest, and is safe to use.
BUT
I MUST WARN YOU - SERENADE SMELLS LIKE NASTY FEET. Of course, nasty feet beat the hell out of having PM on your plants.