Photinias are a handsome evergreen when healthy but very susceptible to both fire blight and powdery mildew. Warm, moist weather and poor air circulation encourage these foliage diseases. I suggest you prune the damaged sections back and clean up any fallen leaves to help stop the spread of these diseases. A fungicide spray can be tried but in my experience even using Funginex on photinia in early, mid and late spring could not stop the leaf drop. I no longer recommend this shrub for use in areas where there is high spring rainfall. You may want to replace this disease magnet with a hardier shrub. Another idea is to remove all the lower branches and train your photinia into stardard or tree shapes. Having a bare trunk may allow for better air circulation and foliage away from the ground will be less likely to become infected. Good luck and Keep Growing, Marianne Binetti