What Causes Powdery Mildew?
Powdery mildew fungi seem to be everywhere. They overwinter in plant debris begin producing spores in the spring. These spores are carried to your plants by wind, insects and splashing water. Conditions that encourage the growth and spread of powdery mildew include:
- Dampness or high humidity (Not common during rainy seasons or in extreme heat)
- Crowded plantings
- Poor air circulation
Controlling Powdery Mildew
- Choose healthy plants and keep they growing healthy
- Try and find a powdery mildew resistant cultivar, if your area is susceptible
- Don't plant non-resistant varieties in the shade
Once Your Plants are Infected:
- Remove and destroy all infected plant parts
- Improve air circulation by thinning and pruning
- Don't fertilized until the problem is corrected. Powdery mildew favors young, succulent growth
- Don't water plants from above
- Apply a fungicide: There are many fungicides available. Check the label to be sure they are safe and effective on the type of plant that is infected. Look for ingredients such as: potassium bicarbonate, neem oil, sulfur or copper. There are also chemical fungicides, such as triforine, that can be used on ornamental plants. There is also a home remedy made from baking soda that is effective.Most fungicides will need repeat applications every 7 - 14 days, for continuous protection. Always follow the label instructions for both application and waiting period before harvest
Hope this helps man...good luck it sucks, I thought I had PM one time, it ended up being green aphids, they're hard to see and excrete a liquid that turns whitish like PM, if it turn out to be that there's a crazy stupid fix...1 teaspoon of garlic powder in a gallon of water, mix very well, and spray, it kills em on contact and I found my plants love it...go figure, most nutes are salt based anyhow 
...see I treated it like school and here I am in jr high now...lol...
