A fungal disease of photinia, hawthorns, and other related plants. It primarily hits large monoculture plantings. It can be controlled by improving soil conditions and avoiding susceptible plants. It is most active in spring and fall. Use the Sick Tree Treatment and try to avoid watering the foliage.
It shows up on the foliage as round dark purple spots. Baking soda or potassium bicarbonate spray will stop the spotting on the leaves if caught early. Improving the health of the root system with aeration, compost and rock powder is the long range cure. Products containing alfalfa will also help. Use the Sick Tree Treatment for ultimate control.