WSU Extension

Hortsense

Azalea : Ovulinia petal blight
(revision date: 3/10/2017)


Biology
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

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
    - hide images

+ Show larger images

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