Downy mildew symptoms on a cucurbit leaf
Downy mildew on dog rose leaves
Basil leaves attacked by mildew
Close-up of basil leaf attacked by mildew
Contents
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Downy mildew
Contents
Find all our tips in the application
When mildew invades the garden, it spares almost no one. All species, from vegetables to fruit trees to roses, can be infected!
Downy mildew is a cryptogamic disease, i.e. It is caused by fungi or micro-organisms called oomycetes. Several parasites of the same family are grouped together under the term mildew. There are different types of downy mildew: downy mildew on grapes, downy mildew on potatoes and downy mildew on tomatoes, also known as Phytophthora infestans.
Contributing factors
Downy mildew spreads in humid, hot weather, generally when humidity is over 90% and temperatures are between 10°C and 25°C.
How it works
When infecting plants, mildew fungi :
- deform shoots ;
- cause leaves to drop ;
- delay fruit ripening.
Downy mildew reproduces by means of its spores. It spreads a mycelial filament that contaminates plants by penetrating their tissues.
Symptoms
The fungus appears on the upper surface of the leaf blades. It forms small greenish-yellow spots. The underside is covered with a whitish felting. The spots spread to other leaves and fruit, which in turn dry out and rot.
Treatment
Preventive measures
It's easier to prevent mildew than to get rid of it. Here are some simple steps you can take to protect your plants:
- space out plants to aerate your garden and avoid creating a damp environment;
- choose species developed for their resistance to fungus attack;
- water the base of plants, not the leaves;
- plant different varieties next to each other: this way, they won't contaminate each other.
- spray foliage with nettle manure, Bordeaux mixture or a mixture of water and baking soda.
Curative measures
If downy mildew has already reached the crop, cut off infected parts to stop the disease progressing.
To combat downy mildew, you'll need to use fungicidal and toxic products, particularly copper-based.
