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.