Downy mildew of the grapevine

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Downy mildew of the grapevine
Downy mildew on the underside of the leaf

Downy mildew on the underside of the leaf

Systematics
Department : Egg mushrooms (Oomycota)
Class : Oomycetes
Order : Peronosporales
Family : Peronosporaceae
Genre : Plasmopara
Type : Downy mildew of the grapevine
Scientific name
Plasmopara viticola
( Berk. & MA Curtis ) Berl. & De Toni 1888

The downy mildew of grapevine is a plant disease in grapevines . The pathogen is the egg fungus Plasmopara viticola . It is of particular economic importance in viticulture , as it can cause considerable damage. The pathogen originally occurs on wild-growing North American grapevines and was introduced to Europe in 1878 - presumably with grape material that was imported for use as a base to combat phylloxera . The colloquial term Peronospora is derived from the generic name and the original name Peronospora viticola . P. viticola can only feed on living plant tissue of the vine (host-specific) and reproduce on it (obligatory biotrophic way of life).

Symptoms

A leaf attack can first be recognized by lightening on the upper side of the leaf, which is referred to as "oil stains". On damp nights, sporangia carriers develop, which emerge from the stomata ( stomata ), making the underside of the leaf appear as if it has been dusted with flour. Later on, the infested areas necrotic, which significantly reduces the photosynthetic output and thus the sugar storage in the berries. The symptom of "leather berries" arises from the infestation of a leaf before or during flowering or on the young green berries. The berry dries out and the skin becomes leathery and tough. Such an infestation can lead to complete crop failures.

Infection cycle

P. viticola overwinters in fallen leaves on the ground in the form of sexually formed oospores . These germinate in spring at temperatures above 11 ° C and form primary sporangia, which release a large number of flagellated zoospores when they come into contact with water. By splashing raindrops, they reach the underside of the leaf and actively swim through the film of water to the stomata ( stomata ). After attachment, the pathogen forms an infection hypha , with which it penetrates the aerenchyma (respiratory tissue) of the leaf. When it comes into contact with a cell wall, the infection hypha forms an appressorium to penetrate the cell wall and, in close contact with the plant cell, to form a haustorium for uptake of nutrients. This is followed by further intracellular spread with the formation of further haustoria within an intercostal field.

In an asexual life cycle, there is an epidemic spread over the further vegetation period. This leads to the formation of tree-like structures, the sporangia carriers, at the ends of which asexual sporangia constrict. These get onto new vines through wind and rain, in order to release flagellated zoospores when they come into contact with water and trigger new infections.

If there is contact between opposite-sex (heterothallic) hyphae in the plant tissue, sexual reproduction takes place, especially in autumn, from which the hardy oospores for the new infection in the next year emerge.

Combat

The French botanist Pierre-Marie Alexis Millardet accidentally discovered the effectiveness of copper against downy mildew in 1882 and developed the first successful fungicide, Bordeaux broth . Even today, preparations containing copper are used in viticulture and are the approved and efficient pesticides against P. viticola in organic viticulture . Otherwise, other effective fungicides from various classes of substances are now available to viticulture, but they are almost exclusively protective (preventive) and must therefore be applied before infection. This results in a high expenditure on plant protection for the winemaker. Forecast models, such as VITIMETEO, are intended to help winemakers choose the right spray times.

Another way to reduce the use of fungicides is to cultivate fungus-resistant grape varieties . Grape varieties with powdery mildew resistance and very good quality properties are now available. The most successful fungus-resistant grape variety in Germany so far is Regent .

Potassium phosphonate can be used to support the effectiveness of copper applications. The chemical was approved as a plant strengthener for organic viticulture in 2013. In the meantime, however, the German Plant Protection Ordinance classifies the product as a plant protection product and it can no longer be used in organic viticulture.

See also

literature

  • Horst Diedrich Mohr (Hrsg.): Color atlas diseases, pests and beneficial insects on the grapevine . Eugen Ulmer, Stuttgart 2005, ISBN 3-8001-4148-5 .
  • Karl Bauer, Ferdinand Regner , Barbara Schildberger: Viticulture . 9th edition. avBook published by Cadmos Verlag, Vienna, 2013, ISBN 978-3-7040-2284-4 .
  • Edgar Müller, Hans-Peter Lipps, Oswald Walg: Viticulture . 3. Edition. Eugen Ulmer, 2008, ISBN 978-3-8001-1241-8 .
  • Ilse Maier: Practical book organic viticulture . Österreichischer Agrarverlag, Vienna 2005, ISBN 3-7040-2090-7 .
  • Uwe Hofmann, Paulin Köpfer, Arndt Werner : ecological viticulture . Eugen Ulmer, 1995, ISBN 3-8001-5712-8 .
  • C. Gessler, I. Pertot, Michele Perazzolli: Plasmopara viticola: a review of knowledge on downy mildew of grapevine and effective disease management In: Phytopathologia Mediterranea, North America. 50, 2011, pp. 3-44, ISSN  1593-2095 ( fupress.net ).

Web links

Individual evidence

  1. Oliver Bock (2016) Downy mildew: The first organic winemakers report total failures. FAZ-Online , July 30, 2016; accessed on July 31, 2016.
  2. Plant strengtheners .