Powdery mildew on the underside of a vine leaf
Traces of oIdium on a hibiscus leaf
Tomato powdery mildew
Powdery mildew on poinsettia flowers and leaves
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Powdery mildew, a fungus that can be fatal
Contents
Find all our tips in the application
A very common fungal disease, powdery mildew, sometimes called "powdery mildew", attacks a wide range of plants. It is caused by fungi whose filamentous growths invade plants.
The fungi causing powdery mildew (Rysiphe, Microsphaera, Podospharea, Spaerotheca...) belong to the Erysiphaceae family. Although each plant species is affected by a different variant of the disease, the symptoms remain the same.
Contributing factors
Powdery mildew occurs both in winter and summer, in dry and humid weather. A confined atmosphere, humidity-laden air and alternating cool and hot days favor its development. This is why it is particularly active between May and October.
How it works
The fungus spores responsible for powdery mildew spread :
- with the wind ;
- with rain ;
- using non-disinfected gardening tools;
- by plant-to-plant contact.
Powdery mildew attacks leaves first. It also attacks stems and flowers. As colonization accelerates, plant growth is reduced and, in the case of vegetable crops, yields drop. Indoor plants suffer aesthetic damage.
Symptoms
At the onset of infection, powdery mildew is characterized by a whitish felting on the foliage. This floury coating, of varying thickness, covers young tissue, new leaves and flower buds.
Leaves stiffen, deform and perforate. Buds curl up, and flowering is reduced. Trees and shrubs are weakened and their limbs fall off.
Finally, an attack of powdery mildew can be fatal to ornamental or vegetable plants.
Treatment
To prevent the spread of powdery mildew, space plants so they don't contaminate each other, and don't wet their foliage when watering in hot weather.
Powdered sulfur, diluted in water and sprayed on the leaves, is the most effective solution for treating powdery mildew. But you can also use natural treatments.
As soon as the first symptoms appear, cut off and burn the infected leaves. Then mix baking soda, black soap and lukewarm water. Spray on dry foliage to slow the progress of the fungus.
Finally, weekly spraying with a mixture of 10% milk and 90% water makes powdery mildew disappear.
