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mildew

mildew (GB)
mildiou (F)
meeldauw (N)
mildiú (ES)
melata (I)
ferrugem (PO)

Designation for two very dangerous, by mushrooms caused vine diseases. They come from North America and were introduced to Europe with contaminated vine material only in the second half of the 19th century. Both types of fungi are among the biotrophic parasites that means that they feed on living cells of the infected host. The two mildew diseases are often confused, less because of the disease symptoms, which are fairly obvious, but because of the confusingly similar names. There are plant-specific powdery mildew fungi, for example for apples, peas, cucumbers, roses, spinach and vines. The mushrooms are strictly host-specific, meaning they can only live on their host.

The two diseases get along in the classic way sulfur (Powdery mildew) and copper sulphate or. Bordeaux mixture (Downy mildew) fought. Increasingly, but also special fungicides or Plant strengtheners used. In the growing season, control often has to be repeated several times. At the intersection of new varieties will also be on today resistance value against both types of mushrooms. It should be noted that some types of ladybug that's the most important beneficials in viticulture count, feed exclusively on mildew. But this has no meaning in the fight in the vineyard.

Powdery mildew (Oidium)

The powdery mildew is also called "Oidium" or "Oidium tuckeri" after the gardener William Tucker named, who first discovered the fungus in 1845 in England. The causative agent of the disease is one of the ascomycota fungi, the botanical name is "Erysiphe necator var. Necator" or "Uncinula necator var. Necator". The fungus was already identified and described in 1834 in North America. He was probably introduced to Europe in the early 1840s via England and spread rapidly throughout the continent. This led together with the also from North America a few years later phylloxera a true disaster in European viticulture. Large parts of the vineyards were destroyed in many countries. In 1854, only one-tenth of the normal amount could be harvested from the damage caused by powdery mildew in France. Later, two more plagues originating from North America were added, namely downy mildew and black rot,

Genuine Merhltau (Oidium) - Symptoms on the grapes and leaf

The powdery mildew affects all the green parts of the vine, especially on hot days with cool nights. He prefers dry conditions, which is why he is also called "fair weather mushroom". However, he does not like a sunny location, which is why a dense foliage roof encourages its development. The transparent, cobweb-like network (mycelium = sum of all hyphae) covers young shoots, leaf surfaces and depending on the time of infestation also the petals and the still green, unripe berries. After about two weeks gray-white, flour-like spores appear. The leaves They look like dusted with flour or ashes. That is why the disease is also called "ashen."

The fine white threads (hyphae) send suction organs into the epidermal cells of the vine. Here, the nutrients that the fungus needs for its nutrition are absorbed. The result is growth disorders and distortions of the affected parts, which in extreme cases cause the leaf to die prematurely. In heavy infestations, the entire shoot is purple violet. This happens before the blossom, become fruit set and earnings severely impaired. The berry development is slowed down, the berries jump up and dry up. The wind blows the spores and spreads the disease quickly. The overwintering of the fungus occurs as a mycelium between the bud scales. The wine from infested grapes has a typical unpleasant odor and Schimmel taste, therefore, a selection is recommended.

It took over ten years to be considered an effective antidote with the pollination sulfur recognized. Anyone who had the groundbreaking insight is unclear, because there are several people who are claimed by their countries as "inventors". One of them is the Frenchman Comte de la Vigne, whose vineyards were heavily infested in the Médoc. He developed the solution in lengthy trials. From 1857, then the sulfurization in Bordeaux was generally applied. Another is the Austrian nobleman Ludwig von Comini (1814-1869), who finished his research with the same result in 1865 and therefore received the apt epithet "Sulfur Apostle". In dry climate Sulfur dust is used in precipitation-rich so-called wettable sulfur, For preventive control is a breezy education of the vines.

Certain species of American vines are largely resistant, numerous Europeans Vines but susceptible to it (without finishing with American rhizome). In particular, these are the grape varieties Cabernet Franc. Colombard. Chardonnay. Chenin Blanc. Elbling. Kerner. mazuelo. Müller-Thurgau. Blue Portuguese. Scheurebe. St. Laurent. Sylvaner and Trollinger, However, the varieties have a certain resistance Aramon Noir. Cabernet Sauvignon. Cot. Merlot. Syrah. Tempranillo. Pinot Noir and Riesling,

Downy mildew (Peronospora)

Thirty years later followed by the 1878 imported from America to the South of France Mildew (downy mildew English). Other names are "Peronospora" or "vine Peronospora", or occasionally "leaf fall disease", "Dürring" or "Lederbeerenkrankheit". The pathogen belonging to the fungal fungal (Oomycota) is called "Plasmopara viticola". The mushroom turf is similar to the powdery mildew, so it was named after initial confusion with the "real" as "wrong". The fungus was created in 1878 by the French botanist Jules Émile Planchon (1823-1888) determined. In just ten years it spread throughout Europe.

Downy mildew (Peronospora) - symptoms on grapes and leaves

In contrast to the real thing, downy mildew ideally needs moist conditions. The occurrence and growth is particularly favored by spring thunderstorms with heavy rain and a humid weather. The fungus therefore occurs mainly in northern European countries with such an environment. On the upper side of the leaf, circular yellowish spots appear, which resemble oil spots. The fungus breaks down the chlorophyll, causing the leaves lose the green color, become yellowish and translucent and wither (hence the name Dürring). In contrast to powdery mildew, the mouse gray-bluish, fluffy mold lawn forms in compact areas only on the underside of the leaves.

It consists of nothing but spores, which are attached to a stalk like a tree. These continue the cycle, which can be completed about eight times a year. The aggressive spores penetrate with their flagella over the stomata very deep into the host tissue. The mycelium spreads in the tissue. It can also affect the inflorescences (notes) and fruits. This causes a complete foliage loss (therefore leaf fall illness) as well as small, shrunken and leather-like berries (therefore also leather berry illness) and impairs the wood maturity of the shoots, The spore containers (sporangia) are carried by wind and rain on other plants, so that the mushrooms spread very quickly in a vineyard.

The mushroom hibernates as a winter spore in the fallen leaves and leather berries and matures in the spring. In 1885 the first time was a fight by means of the botanist Alexis Millardet (1838-1902) developed copper lime broth. The agent was first successfully used in Bordeaux on a large scale, from which the popular term Bordeaux mixture derived. For downy mildew, many European vines are vulnerable, especially Chasselas. Müller-Thurgau and Blue Portuguese, A good resistance to perfect resistance own the American species Vitis cinerea var. Helleri. Vitis rotundifolia and Vitis rupestris,

Powdery mildew left: © André Mégroz
Powdery mildew right: © Christoph Hoyer
Downy Mildew: © Christoph Hoyer

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