This is the information posted on Dirt Doctor web site from Howard. Control: Cultural practices can reduce the chance for this disease. The best control is prevention. Do not plant photinia or Indian hawthorn areas that accumulate water, or have poor drainage. Red tip photinia are susceptible to cotton root rot (Phymatotrichum omnivorum) and this fungal disease is exacerbated by poor drainage. Damage from this root disease can lead to weakened plants that are subsequently more susceptible to problems such as leaf spot. Space plants to improve air circulation around them and to promote rapid drying of leaves. Do not water or fertilize more than necessary to avoid promotion of excess new growth, which is more susceptible to disease. If plants require supplemental irrigation, water early in the morning so the leaves dry quickly. Fallen diseased leaves can be removed as they are a potential source of future infections, but are not the most significant source. Moving them could cause an unintended dispersal of more spores. You may try covering fallen diseased leaves with cedar mulch to accelerate their decomposition and suppress the fungus. Use a potassium bicarbonate spray on the foliage of heavily infected plants (4 teaspoons/1gallon water), or corn meal juice. It may be necessary to remove severely diseased plants that have also been damaged by cold injury and replace them with another plant species not susceptible to the disease. Improve your soil health by following the basic organic program.
***A Word from Howard - Although I wouldn’t buy or plant any more red tip photinia, my photinia program, which evolved into the Sick Tree Treatment, can save the plants and bring them back into a healthy condition. If the root system of the plant is too damaged, however, then the plant may need to be removed. The reason for the acceleration of photinia problems is the unfortunate continued use of harsh synthetic fertilizers and toxic pesticides. Not only do those products not solve the problem, they make it worse. The real problem is not the spots on the leaves, the subsequent chlorosis, or the foliage die back. These are merely symptoms of the real problem.
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