Genus name (botanically Botryotinia) for fungi with around 20 species (types) that belong to the tubular fungi or moulds. All species live as parasites, which leads to the progressive decay of the tissue (rot) of the infested plants. The species Botrytis cinerea (also Botryotinia fuckeliana, grey mould, grey rot, grey mould rot, sour rot when grapes are still green) is a plant pest that attacks well over 200 host plants, including grapevines. The mycelium (fungal threads, tissue) is greyish or brownish. The fungus spreads mainly vegetatively via the conidia (spore form). Some species can also reproduce sexually.
Occurrence
Botrytis was already described in the 18th century and occurs in all temperate climate zones of the world. Wine-growing regions with particularly favourable geographical and climatic conditions for infestation include Sauternes (France), Rheingau (Germany), Neusiedlersee (Austria) and Tokaj (Hungary). Flower bulbs, vegetables, ornamental plants and vines are particularly affected. The infestation is necotrophic (fatal) in young grapes and biotrophic (host organism stays alive longer) in older grapes.
Infestation of the vine
All parts of the vine except the trunk and the perennial wood are attacked, but preferably flowers and (at all stages of ripening) berries. This is because there is a sufficient supply of sugar and nitrogenous compounds on these. The name grey mould is derived from the characteristic grey fungal turf that covers the infested plant parts. Even a light breeze causes a grey cloud of fungal spores to rise, spreading the spores quickly and widely and infecting other vines and plants.
Time
Botrytis is feared in viticulture, but can be very desirable "at the right time". Depending on the stage of ripeness or the infested areas on the vine, there are also the self-explanatory terms botrytis on the vine, stem botrytis or grape botrytis. An infestation of the still green and acidic berries is called sour rot. An early attack in summer on berries that are not yet fully ripe spoils the harvest and is referred to as raw rot. Both are undesirable.
Sour rot
An infestation of the still green, small and sour (hence the name) berries can cause major yield damage. This is "noble rot at the wrong time". It starts in the centre of the bunch and is then transferred from berry to berry. The fungus spreads in the pulp, breaks through...
