Most commonly used abbreviation for Botrytis cinerea (synonym Botryotinia fuckeliana) for what in German is called gray mold rot (also gray rot, gray mold, acid rot) or positively occupied as noble fungus or noble rot mold from the genus Botrytis. It belongs to the tubular mushrooms and spreads vegetatively over the so-called conidia (spore shape). Depending on the stage of ripeness or the affected areas on the vine, it is also known as a botrytis, stem botrytis or grape botrytis. It was already described in the 18th century and occurs in all temperate climates around the world. Wine-growing regions with geographic and climatic conditions that are particularly favorable for infestation Sauterne (France), Rheingau (Germany), Lake Neusiedl (Austria) and Tokaj (Hungary). Over 200 host plants are known. Bulbs, vegetables, ornamental plants and vines, Young grapes are necotrophic (lethal), older ones biotrophic (host organism stays alive longer).
At the Rebstock all parts except the trunk and the perennial wood are affected, but preferred blossoms (if the fungus occurs at this point) and berries. Because there is a sufficient supply of sugar and nitrogen-containing compounds. The name gray mold comes from the characteristic gray mushroom lawn that covers the affected parts of the plant. In the case of heavy grape infestation, it can be observed that when the reading container is emptied, a gray cloud consisting of the fungal spores rises. In viniculture, botrytis is feared on the one hand, but on the other hand "at the right time" is also very desirable. Under appropriate environmental conditions, the noble rot mainly desired in white wine varieties arises. This is a prerequisite for noble sweet White wine specialties such as outbreak. choice. Beerenauslese and (a must under wine law) Trockenbeerenauslese, Due to the high sugar content, the botrytis wines are among the sweet wines, With these is the caramel-like Botrytiston (also brittle ) Expressly desired.
Prerequisite is a late infestation of already ripe berries from around 80 ° Oechsle (16 ° KMW) in dry autumn weather. Long-lasting rains in particular from the end of August offer ideal conditions. Ideal are dry and cool nights, in which the mushroom growth slows down, and warm and humid days with 20 to 25 ° Celsius, in which the mushroom grows faster again. The fungus attacks individual berries and from there spreads very quickly to the whole grape. A second source of infection are infected, dead flower remnants inside grapes. Infections often go from feeding spots to the caterpillars Grape berry moth through which the mushroom can easily get inside the berries. All botrytis species live as parasites in the tissue of the infected plants. This leads to progressive disintegration or cell death of the tissue (rot).
The skin of the berries is penetrated by tiny pores through which the water slowly escapes. The ingredients are concentrated and the berries are dried up like a raisin. tartaric acid and malic acid are reduced, but the formation of gluconic and Sugar promoted. Botrytis infestation always causes a chemical change and also destruction of the variety-specific flavorings, Nitrogen compounds necessary for fermentation are reduced, which means that part of the sugar remains unfermented. There are relatively strong taste-changing metabolic products. The octenol gives the wine a typical musty mushroom note of mushroom and moist forest floor sotolone a sweet, caramel-like taste. Through certain fungal enzymes anthocyanins and other phenols oxidized and transformed into brownish polyphenols. Only 10% of infested red wine grapes cause a visible change in the color of the wine. That is why botrytis is usually undesirable for red varieties (although there are a few producers).
As a so-called gray rot (Pourriture grise), the botrytis causes great damage in the vineyards when the still unripe berries are infected. This is, so to speak, a "noble rot at the wrong time" and then causes enormous damage. This usually begins in the middle of the grape and is transmitted from berry to berry. The mold spreads in the pulp, breaks through the berry skin and the grapes decompose due to wet rot. Sugar can no longer be stored in the destroyed berry and they remain small and acidic. This is why this is also known as acid rot. The berries turn pink and purple and finally turn brown. In addition, the berries of Acetobacter (Vinegar bacteria). Wine made from it has an unpleasant, stuffy taste; Red wines have a pale, gray-brown color.
A preventive measure is the most comprehensive deprivation of the bases for infection and spread. By appropriate training system and pruning and the resulting good aeration ensures that the grapes can dry quickly after rainfall. This removes the moisture that is essential for the growth of the fungus. Grape varieties with dense foliage (it takes longer to dry after rain) and with dichtbeerigen Grapes (the narrower the berries, the faster they spread) are more at risk. These are e.g. B. Gewurztraminer. Kerner. Müller-Thurgau. Pinot Noir and Scheurebe (Seedling 88).
A new method is to spray the grapes with antimicrobial agents lockerbeerige To obtain grapes (see under phytoalexins ). The spread is also favored by an excessive proportion of nitrogen as well as lack of magnesium in the ground. That's why you pay attention to the fertilization on this fact. The feeding damage of the Grape berry moth the spread, so a reduction must take place. In addition, the control is carried out by appropriate fungicides, this may have to be done several times a year. In the breeding of documents or new varieties will be particularly good resistance (Resistance) against botrytis or mushrooms generally respected. See also under Vine enemies,
Riesling: By Tom Maack Tom , CC BY-SA 3.0 , Link
Botrytis pigeon left: Walliswine - own plant, CC BY-SA 3.0 , link
Botrytis pigeon middle: unknown
Botrytis dove on the right: By Uschi Dugulin from Pixabay
Hand with grapes: © DWI (German Wine Institute)