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Mildew is a nightmare for crops, especially for fruit, vegetables and vines. Knowing how to recognize it is essential to adopt the right treatment. Here are some tips on how to identify late blight.

How to identify mildew in a garden?

How to identify mildew in a garden?

What is mildew?

First of all, we must know what is downy mildew: this name is used to name a set of cryptogamic diseases may affect several plant species. The plants are then attacked by Oomycetes microorganisms. Mildew can cause real epidemics in some species, especially for vines, fruit trees and some vegetables (tomato, squash, potato).

How is late blight manifested?

In case of attack of mildew, we can see the appearance of brown spots on the affected plants. The leaves can also be covered with white mold and cottony appearance. If no action is taken, the affected areas eventually wilt (either leaves or twigs): the whole plant eventually rot. In any case, the tuber deteriorates very quickly and becomes very smelly.

Causes of mildew

Mildew is a disease that is usually caused by the attack of microscopic parasites belonging to the category of Oomycetes, family Chromista, which share characteristics very similar to mushrooms. In jargon, it is referred to as "parasitic fungi" possessing the characteristic of multiplying very quickly when certain conditions are met (high humidity and temperature oscillating between 12 and 25° C). The spread of the disease is done by the spores produced by Oomycetes. Be careful, they can withstand the winter, fixing on the plant debris and reactivating as soon as the good weather returns.

These parasites causing blight show a high sensitivity to copper, which is why gardeners use Bordeaux mixture in treatment.

Plants that may be affected by mildew

Mildew can "attack" a multitude of plants, the gardener or the farmer must then be vigilant. Here are some species more particularly concerned by mildew:

  • Vine (Plasmopara viticola)
  • potatoes (Phytophthora infestans)
  • the vegetables: beetroot, carrot, spinach, artichoke, celery, onion...
  • the fruits: apricot, strawberry, peach...
  • sugar cane
  • alfalfa
  • hellebore
  • citrus fruits

An epidemic of late blight in potato crops caused a great famine from 1845-1849 in Ireland. Fortunately today, late blight is limited and eradicated by preventive treatments or fungicide products.

Now that you know how to identify downy mildew, check out our article on the different treatments available to eliminate this disease from your garden: "The treatments against mildew".


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