DISEASE

NAME
Petal Blight in Azalea
Ovulinia azaleae


Description
A fungal problem that produces black sclerotia that is up to 4mm across, and overwinters tolerating cold conditions.

Symptoms
Only the buds and flowers are attacked forming small circular spots that are brown on pale coloured flowers and white to cream on dark coloured flowers. The spots enlarge quickly and engulf the entire flower, during humid periods becomes slimy and black sclerotia may develop in the petals. The infected flower then dries out and persists on the plant unlike unaffected flowers that fall after blooming.

     Rhododendron Kurume Hybrids

Source and Dispersal
It is found on other infected plants and the sclerotia may overwinter in the soil or leaf litter. The spores are dispersed by wind.

Favoured Conditions
It prefers warm humid to wet conditions.
     
Affected Plants
It attacks Azaleasparticularly Kurumes and Indicas cultivars and may be found on some Rhododendronspecies.

Non-chemical Control
It is difficult to control but it may be limited by the removal of infected flowers and plants.

Chemical Control
Preventative spraying of a fungicide such as triadimefon is the only way to control the problem. Follow up applications may be required.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.