White Fungus on Red Tip Photinia

Disease Identification

• Red tip photinia is prone to a powdery mildew fungal disease. The disorder may be caused by a variety of fungi, all of which lead to similar symptoms on affected plants. According to the Colorado State University Extension, powdery mildew is among the most common and easily recognized plant disorders that affects nearly all landscape plants, including shrubs, trees, crops, weeds and herbaceous plants.

Symptoms

• The disorder starts with the appearance of white or gray, talcum-powder-like patches on foliage surfaces. As the disease progresses, the patches grow in size to cover the entire leaf surface. The powdery, fungal growth also spreads to leaf undersides and to the stems. Pinhead-size, brown to black fungal fruiting bodies are visible within the powdery fungus. Affected foliage starts to yellow and distort with premature leaf drop.

Favorable Conditions

• Certain cultural conditions favor development of disease in red tip photinia. Crowded shrubs that are planted in damp, shaded sites with poor ventilation are highly prone to infection. Disease chances increase under temperatures of 60 to 80 degrees Fahrenheit. The fungal spores do not tolerate extreme sunlight, heat and temperature above 95 degrees Fahrenheit.

Management

• Improving cultural conditions is among the important disease management strategies. Plant red tip photinia in well-ventilated, sunny sites. Do not fertilize too late in the season with nitrogen, as this encourages succulent growth that is more prone to the disorder. To reduce humidity, avoid the use of overhead irrigation. In cases of severe infection, use recommended fungicides, such as sulfur-based products, potassium bicarbonate, triforine or neem oil.