Mostly used abbreviation for Botrytis cinerea (synonym Botryotinia fuckeliana) for in German as gray rot (also gray mold, gray mold, sour rot) or positively occupied as noble mushroom or noble rot mold from the genus Botrytis. It is one of the ascomycetes and spreads vegetatively over the so-called conidia (spore form). Depending on the maturity stage or the affected areas on the vine, it is also called Gescheinsbotrytis, Stielbotrytis or Traubenbotrytis. It was already described in the 18th century and occurs in all temperate climates in the world. Winemaking areas are particularly favorable for infestation geographic and climatic conditions Sauterne (France), Rheingau (Germany), Lake Neusiedl (Austria) and Tokaj (Hungary). There are over 200 host plants known. Particularly affected are bulbs, vegetables, ornamental plants and vines, In young grapes, the infection affects necotrophic (deadly), in older biotrophs (host organism stays alive longer).
At the Rebstock All parts except the trunk and perennial wood are infested, but preferred blossoms (if the fungus occurs at this time) and berries. Because there is a sufficient supply of sugar and nitrogenous compounds. The name gray mold arises from the characteristic gray mushroom lawn, which covers the infested plant parts. In case of heavy grape infestation, it can be observed that a gray cloud consisting of the fungal spores rises when the receptacles are emptied. In viticulture Botrytis is on the one hand feared, on the other hand "at the right time" but also very desirable. With appropriate environmental conditions, the noble rot, which is mainly desired for white wine varieties, is produced. This is partly a prerequisite for noble sweet White wine specialties like outbreak. choice. Beerenauslese and (legally required) Trockenbeerenauslese, The Botrytis wines are due to the high sugar content of the sweet wines, In these is the caramel-like Botrytiston (also brittle ) Expressly desired.
Prerequisite is a later infestation of already ripe berries from about 80 ° Oechsle (16 ° KMW) in dry autumn weather. Especially long-lasting rains from the end of August offer optimal conditions. Ideal are dry and cool nights, in which the mushroom growth slows down, and at 20 to 25 ° Celsius warm and humid days, in which the fungus grows faster again. The fungus infests individual berries and spreads from there very quickly to the whole grape. A second source of infection is infected dead leaves in the interior of grapes. Often infections of feeding sites of the caterpillars of the Grape berry moth through which the fungus can easily reach the berry interior. All Botrytis species live as parasites in the tissues of infected plants. This leads to the progressive decay or cell death of the tissue (rot).
The berry skin is penetrated by tiny pores, through which the water escapes very slowly. The ingredients are concentrated and dried the berries like raisins. tartaric acid and malic acid are reduced, however, the formation of gluconic and Sugar promoted. Botrytis infestation always causes a chemical change and also destruction of the variety-specific flavorings, Nitrogen compounds required for fermentation are reduced, leaving part of the sugar undegraded. There are relatively strong taste-altering metabolites. The octenol gives the wine a typical musty mushroom note of mushroom and damp forest soil, the sotolone a sweetish, caramel-like taste. Become by certain mushroom enzymes anthocyanins and other phenols oxidized and transformed into brownish polyphenols. Already only 10% infested red wine grapes causes a visible change in the wine color. This is why Botrytis is generally undesirable in red varieties (although there are a few producers).
As a so-called gray pillar (French Pourriture grise) causes the Botrytis great damage in the vineyards, when the still unripe berries are attacked by. 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 transferred from berry to berry. The mold spreads in the pulp, breaks through the berry skin and rotten by an occurring wet rot the grapes. Sugar can no longer be stored in the ruined berry and it remains small and sour. Therefore, this is also referred to as sour rot. The berries turn pink and purple and eventually turn brown. In addition, the berries of Acetobacter (Vinegar bacteria) are attacked. The wine produced from it has an unpleasant, stuffy taste; Red wines have a pale, greyish brown color.
A preventive measure is the most complete removal of the bases for infection and spread. By appropriate training system and pruning and resulting good aeration is achieved that the grapes can dry quickly after rainfall. This deprives the mushroom of its moisture-based basis for its growth. Grape varieties with dense foliage (the drying after a rain lasts longer), as well as with dichtbeerigen Grapes (the tighter the berries, the faster they spread) are more at risk. These are z. B. Gewurztraminer. Kerner. Müller-Thurgau. Pinot Noir and Scheurebe (Seedling 88).
A new process is spraying the grapes with antimicrobials to lockerbeerige To obtain grapes (see under phytoalexins ). Likewise, the spread is promoted by excessive share nitrogen as well as lack of magnesium in the ground. That is why you pay attention to the fertilization to this circumstance. Likewise favor the feeding damage of the Grape berry moth the spread, so that a reduction must be made. In addition, the fight is carried out by appropriate fungicides This may need to be done several times a year. In the breeding from documents or new varieties will especially look forward to a good one resistance (Resistance) against Botrytis or mushrooms generally respected. See also below Vine enemies,
Riesling: By Tom Maack Tom , CC BY-SA 3.0 , Link
Botrytistraube left: Walliswine - own work, CC BY-SA 3.0 , Link
Botrytis grape middle: unknown
Botrytistraube right: From Uschi Dugulin on Pixabay
Hand with grapes: © DWI (Deutsches Weininstitut)