I have found that a mixture of 3% hydrogen peroxide with insecticidal soap works very well at controlling both powdery mildew and insect pests. I buy 27% h2o2 at the local farm supply and dilute it 1 quart to 9 quarts water, and add the insecticidal soap in my backpack sprayer. I spray all my fruit trees at the first hint of the fungus, and this keeps the trees happy for several weeks. I too am in the PNW.
I have found that a mixture of 3% hydrogen peroxide with insecticidal soap works very well at controlling both powdery mildew and insect pests. I buy 27% h2o2 at the local farm supply and dilute it 1 quart to 9 quarts water, and add the insecticidal soap in my backpack sprayer. I spray all my fruit trees at the first hint of the fungus, and this keeps the trees happy for several weeks. I too am in the PNW.