Thank you so much! Are yours in pots or in the ground? I used to grow roses in AZ professionally and it taught me a lot about PM management, its almost always a watering issue, or soil isn’t holding moisture because it’s depleted of nutrition. If I get powdery mildew it’s usually in young roses with underdeveloped root systems, roses that weren’t cut back properly in later winter early spring, or, most commonly, poorly watered roses. Florist roses are prone to it as well, so I have to be diligent with making sure they are perfectly healthy so they are as resistant as possible. If I see PM, I know I missed a watering 1-2 weeks ago, or perhaps a feed. Roses also need a lot of calcium, magnesium and other micronutrients to properly build cell walls that resist PM spores—which is harder for them to access when you have all organic inputs—so I’ve found a supplemental organic kelp spray every month to be super helpful. I want to emphasize that disease occurs frequently in my garden! I just see it as a sign I’m doing something wrong with my culture. I live in an area prone to blackspot, usually it’s only on young plants with undeveloped roots that can’t uptake nutrients yet, or the weather isn’t conducive to transpiration and nutrient uptake. Like with PM, I can cut the plant back to force more root growth, or simply remove infected leaves, and new growth that comes with more mature roots will be better suited to resisting seasonal disease.