Powdery mildew: what exactly is it?
Also called white rot or
powdery mildew,
powdery mildew is a cryptogamic disease caused by different fungi of the
Erysiphaceae
family .
It can be recognized by the white, powdery spots appearing on the leaves, which can deform and fall.
Stems, flowers and fruit may also be affected.
By weakening plants, powdery mildew reduces harvests in the vegetable garden and harms the ornamental appearance of plants.
It often appears at the end of spring, around May, or at the end of summer, in September.
Although it is
harmless to humans,
this common disease affects many plants:
In the vegetable garden:
squash, zucchini, cucumber, tomato…
In the orchard:
vine, apple tree, gooseberry bush, oak…
Ornamental plants:
rose bush, aster, phlox, mahonia…
Also read: Tomato diseases: the twelve you need to know
Powdery mildew can be recognized by the white, powdery spots that appear on the leaves of affected plants.
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What causes powdery mildew?
Powdery mildew develops when the weather is
fairly humid (70 to 80% humidity) and warm enough.
Significant temperature differences between day and night also favor its development.
It spreads more easily in confined areas, where air circulation is poor.
Certain measures can prevent powdery mildew:
Space the plants out to promote good ventilation between the plants;
Remove the affected parts at the start of the infestation, to limit the spread;
Disinfect your tools;
Do not overuse
nitrogen fertilizers,
which encourage the appearance of powdery mildew;
At the end of the season, remove the affected plants to limit the winter preservation of the fungus;
Take care when watering and maintaining your plants: in good health, they are more resistant;
Mulch the plants and water at the base, avoiding wetting the leaves;
If possible, opt for plants that are resistant to powdery mildew.
Powdery mildew develops when the weather is fairly humid (70 to 80% humidity) and warm enough.
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No use without permission.
How to get rid of powdery mildew naturally?
6 solutions
Milk:
thanks to its antifungal properties, milk is an excellent ally in the fight against powdery mildew.
Simply dilute it to 10% in water, then spray the mixture on the leaves every week until the symptoms disappear.
It is also possible to use it as a preventative measure, once a month.
Treat preferably early in the morning, and use skimmed or semi-skimmed milk to avoid odors;
Horsetail decoction:
a horsetail decoction is ideal as a preventative measure, or as a curative measure at the very beginning of a powdery mildew attack.
Macerate 100 g of fresh horsetail in 1 liter of water for 24 hours, in a covered container.
Then boil for 30 minutes, let cool and filter.
Dilute the decoction to 10%, then spray every 15 days.
This decoction can only be kept for 2 weeks;
Garlic decoction:
to prepare a garlic decoction, macerate 100 g of crushed garlic in 1 liter of water for one hour.
Boil for 20 minutes, then let cool before filtering.
Dilute the decoction to 20% before spraying it on the plants:
Baking soda:
the alkaline pH of bicarbonate helps block the development of powdery mildew.
Mix 1 to 2 teaspoons of baking soda and 1 tablespoon of black soap or oil per liter of water.
Spray this solution on the leaves once a week, for 3 to 4 weeks;
Sulfur:
sulfur is not harmless for fauna and flora, but it can be used in organic farming, provided that the doses prescribed on the packaging are respected.
It comes in the form of a powder to be diluted in water, and is preferably sprayed in the morning or evening, at temperatures below 25°C;
Essential oils:
essential oils of orange, savory, garlic and tea tree help naturally fight powdery mildew, including as a cure.
Mix 20 drops of essential oil in black soap or oil, then add this mixture to a liter of water.