I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
The disease on your Red Tip Photinias is called entomosporium leaf spot. It causes the plants to defoliate and thus weakens them over time. The disease infects the foliage primarily during rainy weather and the spots appear later as the infection progresses. Entomosporium leaf spot is not easy to control with sprays, requiring repeated applications during rainy periods. Some gardeners choose to replace their red tip photinias with other species that are not susceptible to this disease. If you choose to try and manage it with sprays you will need to alternate fungicide sprays of either triforine (Funginex) or bayleton with chlorothalonil (Daconil, Bravo, Multi-Purpose Fungicide) every week during the rainy season in spring to early summer and again in fall. Rake up and discard any fallen infected leaves to minimize the amount of innoculum (spores) in the area of the bushes. Avoid species that are susceptible to the disease when you select shrubs for the landscape. In addition to red tip photinia the disease affects Indian hawthorn and cleyera.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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