Ovulinia petal blight affects the flowers only (not leaves or shoots) of azaleas and rhododendrons. Infected flowers first display small, water-soaked spots which enlarge quickly. The petals quickly become slimy and turn brown, sometimes within two or three days after fully opening. The infected blossoms remain on the plant and later provide a source of infection for next year's flowers. Flowers on lower branches are affected first. The disease overwinters in dead flower material or top layers of mulch, and is favored by high humidity.

Management Options

Non-Chemical Management

Remove and destroy all infected flowers from plants and from the ground.
Remove top inch of soil or mulch from beneath infected plants and replace it with clean material.
Avoid overhead watering.
Space plantings and prune to provide good air circulation in and around plants.

Select non-chemical management options as your first choice!

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

Apply protective fungicide just before budbreak and then at recommended intervals during bloom period.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

Bonide Fung-onil Multi-Purpose Fungicide Conc
Active ingredient: chlorothalonil | EPA reg no: 60063-9-4
Captan 50% WP Fruit & Ornamental
Active ingredient: captan | EPA reg no: 4-459
GardenTech Daconil Fungicide Conc
Active ingredient: chlorothalonil | EPA reg no: 67572-82-71004
Ortho Max Garden Disease Control Conc
Active ingredient: chlorothalonil | EPA reg no: 239-2522
Spectracide IMMUNOX Multi-Purpose Fungicide Spray Conc
Active ingredient: myclobutanil | EPA reg no: 9688-123-8845
This list may not include all products registered for this use.

Images

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Caption: Azalea Ovulinia petal blight Photo by: R.C. Linderman

WSU Extension

Hortsense