Powdery mildew or white mildew is a fungal disease of plants that can occur at any time and every year. Let’s see better what it is, how to prevent and remedy it before it is too late.
What is Oidium?
It is also called white malt or albugine and is a fungal disease that attacks plants, caused by imperfect fungi known as “Oidium”.
To recognize a small plant attacked by the Oidium is not difficult, on the contrary, it is very simple, because it will be visible a white powdery powder on the leaves and for this reason the disease is also called mal bianco.
This generates a weakening of the plant itself, which, if sick, will have a slowed and decomposed growth of the branches, pale and deformed flowers. The leaves attacked by the powder will dry up and if not treated promptly, the disease will spread throughout the plant.
What makes the white mal frightening is that it has a life cycle that can last all year round. In winter it begins its cycle on the dry and old parts of the plant, for example fallen leaves and wilted flowers, and then spreads in spring with rising temperatures, releasing the spores that can be carried by the wind to other plants.
Also the high level of humidity and the climatic changes during the summer period, can favor the appearance of this fungus. Also the fog which frequently forms during the nights of the summer months, wets the leaves facilitating the appearance of the Oidium.
Which plants are most affected?
The white mallow affects many varieties, both horticultural and ornamental.
The most exposed garden plants: spinach, radicchio, celery, carrot, chard, parsley, sage, fennel, thistle, vine, pumpkin, zucchini and peach.
The most exposed ornamental plants: pink, maple, hawthorn, hydrangea, chrysanthemum, begonia, zinna, dahlia and calendula.
How To Prevent
Prevention is the best way to keep away this fungus that causes the Oidium. The first advice, even the simplest is not to irrigate the plants during the hottest hours of the day, as it would cause the ideal humidity conditions for white sickness.
Place the plants in a well ventilated and sunny place at least during the morning hours, avoiding excessively humid places.
For plants subject to this disease, prevention is recommended as early as spring. Powdered sulfur can be administered before flowering, and the same operation can be carried out approximately every 3-4 weeks.
The alternatives to sulfur powder are: wettable sulfur or sodium bicarbonate.
How To Use Sulfur
sulfur is the most effective remedy and also an element of organic farming leather allows its use. It is sold either in powder to be used as it is, or wettable that should be diluted with water.
The powdered sulfur is distributed on the plants using a bellows and gloves. It should be used in the absence of wind and during the coolest hours. This formulation as well as having a longer life on the vegetation, is very effective both for prevention in the periods most prone to the onset of disease, both to treat infections already propagated of white malt. Always follow the instructions and dosages written on the packages.
Wettable sulfurs are more suitable for preventive use, and they also have a shorter duration. They should be diluted in water and applied to the vegetation with a nebulizer, always respecting the dosages indicated by the package. Repeat the operation every 5-7 days.
The Sodium Bicarbonate
Sodium bicarbonate is an alternative to sulfur, it has a very effective and immediate action but a low persistence. It is recommended to use it every time there are favourable conditions for the propagation of white mal; for example thunderstorms and high humidity. Dilute a tablespoon of sodium bicarbonate in a litre of water, mix and spray with a nebulizer.
Sodium bicarbonate and sulfur should not be applied during hot hours and in full sun. They would cause burns to the leaves.