Photinia: Powdery mildew
categories: Ornamentals Photinia Photinia Diseases Shrubs
revision date: 2023-02-09 12:00
Photo by: R.S. Byther
Biology
Powdery mildew is a fungal disease found on leaves and shoots of photinia. Characteristic patches of gray-white, powdery fungus are found in thick mats on the upper and lower leaf surfaces. The infected areas may develop fungal fruiting bodies which appear as small black specks on the white mats. Affected leaves may be distorted, turn yellow and drop. The disease is spread by wind-blown spores and is favored by shade, humid conditions, and warm days and cool nights. The fungus overwinters on buds of the host plant and in leaf debris.
Management Options
Use Integrated Pest Management (IPM) for successful plant problem management.
Non-chemical Management
Select non-chemical management options as your first choice!
- Plant in full sun.
- Space plants and prune to provide good air circulation.
- Watch for signs of infection during appropriate weather.
- Prune and destroy severely infected leaves and twigs to reduce spread of disease.
- Clean up and destroy fallen leaves from beneath infected trees.
- Spray upper and lower leaf surfaces with a strong stream of water. Spray only when leaves can dry quickly.
- Do not overfertilize. Powdery mildew is worse on succulent new growth.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- Apply when disease appears. Repeat applications at 7- to 10-day intervals if weather encourages disease (14-day intervals for Spectracide IMMUNOX).
- Homeowners should not make foliar applications to trees over 10 ft tall.
- Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.
Approved Pesticides
Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.