Apple cider vinegar 2 tsp and water in a 1 qt. sprayer would be my 1st choice because someone I know used it. This can be used all the way to the day of harvest.
OR... milk and water 50/50 must spray with lights on, lights cause a chemical reaction in the milk. These are organic ways of fighting wpm but there are probably 50 different over the counter sprays out there
edit == forgot to put hydrogen peroxide 1-4 tbsp per qt water. This is what I use on every grow every few weeks I spray the entire room plants and all as a preservative for many molds, mildew, bugs, and it gives your plants a boost of oxygen and is good for Your plants.