One way to reduce powdery mildew (and rust and some other diseases) is to make sure the plant has good structure (preferably a 'candelabra shape) and most importantly, good airflow. This means that that if you look down the center of the plant from directly above, you can see to the ground. If not, remove as many leaves along the path of the center of the plant. Remove underperforming or weak branches. Also, remove dead leaves, low hanging leaves, and pick up any dead leaves on ground to reduce infection spread. Remember to keep leaves dry, watering ground, not leaves.
If you must use water to rinse leaves, do so early in the day to allow leaves to dry before night time, when most pathogens spread. Doing this should eliminate this problem. Good luck and ‘Happy Gardening’!
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