Powdery mildew of Bougainvillea

Disease Information

Powdery mildew

Symptomsand damage

Powdery mildew is a fungal infection common to most ornamental shrubs. Mildew infections are often caused due to excessive watering of plants and poor soil drainage. Mildew infestations cannot be eradicated for a lifetime. You will have to ensure basic garden hygiene and take some precautions to guard against mildew disease.

SymptomsThe most identifiable feature of mildew infection is the presence of white, powder-like, dusted appearance of the foliage. The infection is more apparent among the leaves than the branches. Crowded branches and dense foliage help in mildew spreading quickly throughout the garden-spread. Root rot is commonly caused by waterlogging in the soil bed but Bougainvilleas rarely suffer from it. However, bougainvilleas suffering from mildew infection often develop root rot due to decreased plant vigor.


You should not use this foliage in the garden compost or for any gardening activity. The best way to reduce chances of mildew infection is to use a fungicide when transplanting the plants. This also helps to prevent root rot infection. Ensure proper drainage in the soil bed. You can increase the soil’s draining capability by adding some dry mulch prepared from wood bits. During damp weather conditions, regularly check for mildew development. You should water the plant minimally during this period. If signs of fungal growth are present, chemical control can be considered. You can use mild fungicides that contain triadimefon or propiconazole as ingredients. During the growing season, regularly check for decaying foliage and clip it with garden scissors but don’t prune. You should prune bougainvilleas before and after the growing season. Ensure that the basal and mid-level foliage is sufficiently pruned to allow greater air circulation within clustered parts of the foliage.


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