Powdery mildew of the grapevine
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Powdery mildew ( Erysiphe necator ) infested young berries |
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| ( Pig. ) Burrill |
The powdery mildew of grapevine is a plant disease in grapevines . The pathogen is the hose fungus Erysiphe necator (syn. Uncinula necator or Oidium tuckeri ( anamorphic )). Other common names are Oidium or Äscherich . In addition to downy mildew and phylloxera, it is one of the main diseases in viticulture .
The pathogenic fungus was originally native to wild-growing North American grape varieties. These grape varieties are mostly resistant to these pathogens. The fungus has also appeared in Europe since 1845. The powdery mildew fungus is widespread in all important wine-growing areas around the world and, if the plant protection is inadequate, it can cause serious economic damage (harvest losses, poor wine quality). Powdery mildew is an obligate biotrophic and host-specific ectoparasite , which means that it can only feed and reproduce on the living plant tissue of the vine. It grows with its hyphae on the plant surface and extracts the necessary nutrients from the plant via haustoria , which it forms in the plant epidermal cells . Infested berries in the harvest can cause negative odor and taste notes in the wine ( mouse , mold, musty tone ).
Symptoms
The infestation is characterized by a white-gray, cobweb-like network on the green plant parts of the vine. Especially shoot tips, small berries and the leaves are easily attacked. Affected shoots remain in their growth, while fruits affected before veraison harden, turn gray or black and burst, so that the kernels are exposed (seed breakage).
Powdery mildew on berries
Left: Berries damaged by Oidium (Erysiphe necator) Right: No Oidium infestation. Due to the infestation, the berry development remains behind and the berries jump up and dry out.
Infection cycle
The fungus overwinters on the one hand as mycelium in infested buds and on the other hand in the form of fruiting bodies (celistothecia - are permanent organs). These fruit bodies are spherical, yellowish at first and dark brown as soon as they are ripe and can already be formed in summer. Most of these permanent organs are formed from the mycelium of the fungus in autumn after the spray season. They overwinter on the bark of the annual and perennial wood, infested leaves, dried-up grapes and grape stalks. The typical oidium stains on the annual wood are meaningless for the winter - but an important point for timely control. Mild and humid winters have a positive effect on wintering.
(a) mature conidia (b) germinating conidia (x) haustorium
In spring, pointer shoots develop, which are covered with a white network of mushrooms. These shoots represent an enormous infection potential. They can cause infections very early. Pointer drives are rare, so new infections in the spring are increasingly important to the celistothecia. If these fruiting bodies do not perish due to leaf fall, pruning, washing or parasitization, they can break open after heavy rain and release numerous ascospores. The temperature range for the development of the fungus (infection, growth, sporulation) is between 7 and 35 ° C, the optimum at 20 to 27 ° C. Many spores are released, especially in dry and warm weather. No water is required for infection. Warm weather with high humidity and always relatively strong nighttime cooling is ideal. Spores that have not yet germinated are washed off by precipitation.
Combat
All European grape varieties ( noble grapevine ( Vitis vinifera subsp. Vinifera )) can be attacked by powdery mildew that has been introduced to Europe, which forces viticulture to use heavy fungicides . Natural resistance can be found in many American wild species as well as in the Asian grape varieties Kishmish Vatkana and Dzhandzhal Kara .
Preventive measures:
The preventive measures include an airy upbringing of the vines, regular vineyard controls, especially in deep, enclosed areas and with sensitive varieties as well as in all vineyards where oidium infestation occurred in the previous year. The timely execution of the foliage work with simultaneous breaking out of the pointer shoots. Pointer shoots are extremely rare and can only be found in very susceptible varieties. Excessive nitrogen fertilization must be avoided. Nitrogen oversupply reduces the resistance to fungal attack. Neglected vineyards in the vicinity can be a significant infection potential for all surrounding vineyards in the event of oidium infestation.
Chemical measures:
For chemical control are sulfur active ingredients or active ingredient combinations and from the groups of substances amidoximes ( cyflufenamid ), Azanaphthalene ( proquinazid ), benzophenone ( metrafenone ), carboxylic acid amides ( boscalid ), quinoline ( quinoxyfen ), dithiocarbamates ( metiram ), pyridinyl Ethylbenzamide ( Fluopyram ), strobilurins ( kresoxim-methyl , pyraclostrobin , trifloxystrobin ) and triazoles ( myclobutanil , penconazole, tebuconazole ) are approved. Most of the active ingredients are almost exclusively protective (preventive) and have to be applied before an 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.
The flowers and especially the small young berries are particularly susceptible to oidium attack. It is therefore about ten days ( BBCH 57) before flowering until berries develop (shot grain size, BBCH 73) the most important period (oidium window) for combating oidium. During this period, the treatment intervals must not be too large. Oidium infestation that is already visible can only be combated with difficulty. Within the oidium window, all grape varieties are very susceptible, as the young tissue can still offer little resistance - even so-called fungus-resistant varieties - against the invasion of the fungus.
| strong | medium | weak |
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| Blauer Portugieser , Blauburger , Müller-Thurgau , Scheurebe , Silvaner | Blauer Burgunder , Blauer Wildbacher , Blaufränkisch , Cabernet Franc , Cabernet Sauvignon , Chardonnay , Frühroter Veltliner , Goldburger , Grüner Veltliner , Merlot , Muskateller , Roter Veltliner , Rotgipfler , Sauvignon Blanc , Syrah , Traminer , Welschriesling , Zierfandler , Rathay , Zweigelt | Neuburger , Riesling , Ruländer , St. Laurent , Weißer Burgunder , Roesler |
Another possibility to reduce the amount of fungicide is to grow fungus-resistant grape varieties (PIWI) . Grape varieties with good resistance to powdery mildew and good quality properties are now available. The most successful fungus-resistant grape variety in Germany so far is Regent . The resistance to fungal diseases in these breeds is only a more or less good to high partial resistance.
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 .
Web links
- Grapevine powdery mildew on hoardship
- More synonyms
- VITIMETEO.de forecast models and weather data for viticulture
Individual evidence
- ↑ Horst Dietrich Mohr: Color atlas diseases, pests and beneficial insects on the grapevine , 2nd edition, 2012, Eugen Ulmer Verlag Stuttgart, ISBN 978-3-8001-7592-5 , p. 93.
- ↑ a b Karl Bauer, Ferdinand Regner , Barbara Schildberger: Weinbau , avBuch im Cadmos Verlag, Vienna, 9th edition 2013, ISBN 978-3-7040-2284-4
- ↑ Coleman et al .: The powdery mildew resistance gene REN1 co-segregates with an NBS-LRR gene cluster in two Central Asian grapevines , BMC Genetics 10 (2009) [1]
- ↑ BVL Plant Protection Product Directory 2013 Part 3 [2]
- ^ Austrian Viticulture Association: Recommendations for Integrated Production in Viticulture, 2010 , Vienna