Brown and wilted flowers on azaleas and rhododendrons are the results of this fungal disease. Forms of petal blight disease are also known to attack camellias and roses in overseas countries. The fungus consists of small hard-fruiting bodies called sclerotia. The spores enlarge rapidly, and by the end of the day, the flowers collapse into a brown, mushy mess.
Petal blight spreads rapidly among these plants at flowering time. Sclerotia can fall to the ground and regrow to reappear the next season to start the next cycle. It can also be worse in wet and cool weather and can move from garden to garden via wind over a long distance. Once the disease appears in the garden it is hard to stop. The best form of defence is to remove damaged flowers as soon as they appear to stop fungal spores from spreading. Dispose of them in a bag in the rubbish.
Other forms of prevention include avoiding wetting flowers when watering (water at the base of the plant), deadheading flowers frequently and applying fungicides as a preventative spray from when the buds begin to colour. There are specific fungicides registered for petal blight.
A healthy garden can also help prevent disease infestation. If your plants are strong and healthy, they may be able to handle and reduce the stress of pests and diseases. Applying Seasol regularly every two weeks during the year can help them to cope with environmental stress. Keeping plants fed with fertilisers such as PowerFeed All Purpose including Natives, better watering and appropriate light exposure can also help build tougher plants.