Thank you for your question. Your plant appears to have powdery mildew, described here: https://pnwhandbooks.org/plantdisease/host-disease/azalea-rhododendron-spp-powdery-mildew. This would be apparent on the top of the leaf. Neem oil might help. But, I suggest you look on the underside of the leaves to detect azalea lace bug, which will only be controlled by neem oil if it is applied on the underside of the leaves at the right time. Here is more information: https://pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/rhododendron-rhododendron-azalea-rhododendron-lace-bug Hope this is helpful. Good luck!
Thank you for the reply. Should I continue neem oil treatment weekly or is there something more effective?
Extension does not recommend baking soda and dish soap; science doesn't indicate it works. You ca use neem oil during the entire growing season. But it doesn't work on azalea lace bugs unless applied on the underside of the leaves, and then only during the right time of their lifecycle. Did you find them?
Yes, I found the azalea lace bugs. Going to do a thorough neem oil spray tomorrow morning.
And keep it up!