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Downy mildew
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 they infect plants, the fungi responsible for downy mildew:
· deform the shoots;
· cause leaves to fall off;
· delay fruit ripening.
Downy mildew reproduces through its spores. It spreads a mycelial filament that infects 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 downy mildew than to get rid of it. Here are some simple steps that can protect your plants:
· Space out your plants to ensure good airflow in your garden and avoid creating a damp environment;
· Choose varieties bred for resistance to fungal diseases;
· Water the base of the plants, not the leaves;
· Plant different varieties next to each other: this way, they won't be able to infect one another.
· Spray the foliage with nettle tea, Bordeaux mixture, or a mixture of water and baking soda.
Remedial Measures
If downy mildew has already affected your crops, cut away the infected parts to stop the disease from spreading.
To control downy mildew, you'll need to use fungicides and toxic products, particularly those containing copper.
