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mildew

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

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

The two diseases are dealt with in a classic way sulfur (Powdery mildew) and copper sulphate respectively. Bordeaux mixture (Downy mildew) fought. But there are also increasing numbers of special ones fungicides or Plant strengtheners used. Control often has to be carried out several times during the growing season. When crossing new varieties will open today too resistance against both types of mushrooms. It should be noted that some types of ladybug that are among the most important beneficials count in viticulture, feed exclusively on mildew. However, this is of no importance when fighting in the vineyard.

Powdery mildew (oidium)

Powdery mildew is also called "Oidium" or "Oidium tuckeri" after the gardener William Tucker named who first discovered the mushroom in England in 1845. The causative agent of the disease is one of the tubular fungi (Ascomycota), the botanical name is "Erysiphe necator var. Necator" or "Uncinula necator var. Necator". The fungus was identified and described in North America as early as 1834. It was probably introduced to Europe via England in the early 1840s and subsequently spread rapidly across the continent. Together with the one that also came from North America a few years later phylloxera to a real disaster in European viticulture. Large parts of the vineyards were destroyed in many countries. In 1854, damage caused by powdery mildew in France could only be harvested by a tenth of the normal amount. Two more plagues from North America came later, downy mildew and black rot,

Common mildew (Oidium) - symptoms on white grape and leaf

Powdery mildew affects all green parts of the vine, especially on hot days with cool nights. It prefers dry conditions, which is why it is also known as the "good weather mushroom". A sunny location does not please him, which is why a dense canopy promotes his 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 appear as if dusted with flour or ash. That is why the disease is also known as "Ascherich".

The fine white threads (hyphae) send suction organs into the upper skin cells of the vine. Here the nutrients that the mushroom needs for its nutrition are absorbed. The result is growth disorders and curvature of the affected parts, which in extreme cases cause the leaf to die prematurely. In the case of severe infestation, the entire shoot is colored violet. If this happens before blossom, become fruit set and earnings severely impaired. The berry development is slowed down, the berries jump open and dry up. The spores are blown away by the wind and the disease spreads quickly. The fungus overwinters as a mycelium between the bud scales. The wine made from infested grapes has a typically unpleasant smell and Schimmel taste, therefore a selection is recommended.

It took over ten years for one to use pollination as an effective antidote sulfur recognized. Who had the groundbreaking knowledge 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 in the Médoc were heavily infested. He developed the solution in lengthy trials. From 1857, sulfurization in Bordeaux was generally used. A second is the Austrian nobleman Ludwig von Comini (1814-1869), who ended his research with the same result in 1865 and therefore received the aptly nickname "Sulfur Apostle". In dry climate sulfur dust is used, in what is known as high-precipitation wettable sulfur, An airy one is used for preventive control education the vines.

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

Downy mildew (Peronospora)

Downy mildew (English: downy mildew), introduced from America to southern France around 1878, followed thirty years later. Other names are "Peronospora" or "Vine Peronospora", or in some cases also "leaf fall disease", "Dürring" or "leather berry disease". The pathogen belonging to the egg fungi (Oomycota) is called "Plasmopara viticola". The mushroom turf is similar to powdery mildew, which is why after being initially confused with the "real", it was called the "wrong". The mushroom was created in 1878 by the French botanist Jules Émile Planchon (1823-1888). In just ten years, it spread across Europe.

Downy mildew (Peronospora) - symptoms on grape and leaf

In contrast to the real thing, the downy mildew ideally needs moist conditions. The occurrence and growth is particularly favored by spring thunderstorms with heavy rain or warm, humid weather. The fungus therefore occurs mainly in northern European countries with such a climate. On the upper side of the leaf, circular yellowish spots appear that 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, only on the underside of the leaf does the mouse-gray-bluish, fluffy mold lawn form in compact areas.

It consists of nothing but spores, which are attached to a stem like a tree. These continue the cycle, which can be run about eight times a year. With their flagella, the aggressive spores penetrate very deeply into the host tissue via the stomata. The mycelium spreads in the tissue. The inflorescences (grains) and fruits can also be affected. This causes a complete loss of leaves (therefore leaf disease) and small, shriveled and leathery berries (therefore leather berry disease) and affects the maturity of the wood 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 ripens in spring. In 1885, the first fight was carried out by the botanist Alexis Millardet (1838-1902) developed copper lime broth. The drug was first used successfully in Bordeaux on a large scale, which is where the popular term came from Bordeaux mixture derived. Many European vines are susceptible to downy mildew, especially Chasselas. Müller-Thurgau and Blue Portuguese, A good resistance to complete resistance own the American species Vitis cinerea var. Helleri. Vitis rotundifolia and Vitis rupestris,

Powdery mildew on the left: © André Mégroz
Powdery mildew on the right: © Christoph Hoyer
Downy mildew: © Christoph Hoyer

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