Help the development of the site, sharing the article with friends!

Mildew is one of the biggest annoyances in the garden. Grapevines in particular are very sensitive to the fungal disease. Read what remedies help against the problem.

Powdery mildew does not only affect the leaves

Table of Contents

Show all
  1. the essentials in brief
  2. detect powdery mildew
  3. combat powdery mildew
  4. prevent powdery mildew
  5. frequently asked Questions

    6. the essentials in brief

    • Wine is particularly commonly attacked by powdery mildew.
    • A basic distinction is made between powdery mildew and downy mildew.
    • The fungal disease is difficult to treat, which is why it is important to cultivate vine varieties that are as resistant as possible.
    • Preventive spraying - for example with baking soda or copper - is also one of the sensible precautions.

    detect powdery mildew

    There are basically two different types of powdery mildew, each of which is a plant disease caused by fungi. Powdery mildew is particularly common on wine and can be easily recognized by the typical, wipeable coating. Powdery mildew is more specialized on certain plant species than downy mildew. The diseases are not only a major problem in commercial viticulture, but also in hobby viticulture, as they significantly impair plant health and the harvest.

    Downy mildew on wine

    Downy mildew is also known as the "bad weather fungus" because it appears from temperatures of 11 °C and after prolonged rainfall or in damp weather. The fungal pathogen Plasmopara viticola is transmitted by rain and can easily invade damp foliage. The fungus does not feed on the nutrients that the plant gives off, but directly invades its cells. Infection typically shows up in early spring. You can recognize downy mildew by these symptoms:

    • mealy, whitish to greyish coating on the underside of the leaf
    • Lightening of the top of the leaf, formation of yellowish spots
    • leaf wilt
    • Death of the still young grapes, so-called leather berries
    • Grapes dry up and become tough with hardening skin
    • if left untreated, the vine can die

    Grapes affected by downy mildew are no longer edible. In addition, the disease is highly contagious.

    Powdery mildew on wine

    Powdery mildew tends to settle on the undersides of leaves

    If you think that your vines are safe from mildew when the weather is nice and dry, you are unfortunately wrong. Powdery mildew, also known as the "fair weather fungus", occurs preferably at temperatures between 20 and 27 °C and sunshine. However, the pathogen Erysiphe necator, which belongs to the sac fungi, also tolerates high summer weather conditions with more than 35 degrees Celsius and can - in the case of an infection from the previous year - appear in spring from as little as 7 °C. You can recognize an infection by these symptoms:

    • Formation of white-grey, wipeable spots on the undersides of leaves
    • These turn grey-brownish at a later stage.
    • These are joined by fine network structures that resemble cobwebs.
    • In addition to leaves, other parts of the plant can also be affected, in particular shoots and grapes, but also buds and flowers.
    • Buds can no longer open after infection.
    • However, an infection always begins with the leaves, which often curl up.
    • Since the fungus deprives the plant of important nutrients, the plant stops growing.
    • The lack of nutrients also leads to the gradual death of the vine.

    Grapes infected with powdery mildew become hard, turn gray to black and are no longer edible due to their unpleasant taste. It can also no longer be used to make juice or wine, as the bitter aroma has a negative effect on the quality of the drink.

    digression

    Which types of wine are particularly sensitive to powdery mildew?

    In principle, all traditional wine varieties are endangered by both powdery mildew and downy mildew. This applies above all to such popular varieties as Chardonnay, Silvaner, Müller Thürgau, Portugieser, Muskateller, Trollinger and Scheurebe.

    combat powdery mildew

    Powdery mildew can usually only be successfully treated in the early stages

    The various types of mildew can be combated very well, at least in the early stages, with well-known household remedies, but later these are no longer of any help. You should definitely remove infested leaves and other plant parts with sharp scissors or similar to prevent further spread. Never dispose of the clippings in the compost, but with the household waste. If the vine is already severely infested, often only a drastic pruning far into the healthy wood helps. Only then is the treatment with sprays carried out.

    home remedies

    "Nature has the right antidote for every problem - without any toxic chemicals."

    If you want to harvest the grapes from your own vine and eat them or process them without fear of poisoning, it is advisable to use proven home remedies. However, these no longer help once the disease has progressed. That is why the regular inspection of vines and the associated early detection of diseases is so important.

    milk

    Fresh whole milk (preferably raw milk!) is a good pesticide that can be used preventively and primarily against powdery mildew in the early stages. Certain bacterial cultures in the milk are effective, which is why you should never use low-fat or heavily processed milk - this simply does not help. That's how it works:

    • Mix whole milk and fresh tap water in a ratio of 1:9.
    • For example, take 100 milliliters of milk and 900 milliliters of water.
    • Put both in a spray bottle and spray the wine with it.
    • Pay particular attention to the undersides of the leaves.
    • Apply the spray several times in a row at intervals of three to four days.

    baking powder

    Baking soda is a good home remedy for mildew

    A solution made from baking powder is also a tried and tested remedy for mildew and is effective against this fungal disease. Proceed as follows:

    • Mix a packet of baking soda (about 10 grams) with a tablespoon of canola oil and a drop of dish soap in a spray bottle.
    • Dilute the mixture with a liter of mineral or tap water.
    • Shake the mixture thoroughly.
    • Spray the vines with it and don't forget the undersides of the leaves.
    • Repeat the treatment every 7 to 10 days.

    Spray preferably in the evening, otherwise the solution can react with the sunlight and leave unsightly stains on the vine leaves.

    digression

    Can you use any baking powder against powdery mildew?

    But be careful: not every baking powder is suitable for treating vines affected by powdery mildew. The baking soda contained only in some varieties is effective, which is why you can also use pure baking soda or baking soda instead of baking powder (which usually contains no baking soda).

    Plant manure or brew

    Plant brews or liquid manure (these ferment for a period of seven to ten days) are also very suitable for preventive spraying or for treatment in the early stages. Use field or marsh horsetail, garlic or tansy for this. How to make the broth:

    • Chop up 300 grams of the fresh plant matter.
    • Chop it as finely as possible, as the active ingredients can then be better dissolved.
    • Pour a liter of hot, but not boiling, water over the material.
    • Let the mixture steep for 24 hours.
    • Strain out the coarse material and spray the plants with the brew.
    • If this is to be used preventively, dilute it with water in a ratio of 1:5.
    • Repeat the spray about once or twice a week.

    More effective, but somewhat more time-consuming to produce, are plant manure, mainly made from field horsetail. This is particularly rich in the effective silicic acid.

    spray

    In addition to the biological sprays mentioned, you can also purchase special antidotes in stores. These are mostly based on the fungicidal effect of the metal copper and can also be used in the case of a stronger infestation. Copper-containing sprays are also permitted in organic farming, but are still toxic due to the high concentration.

    Effectively prevent powdery mildew

    Vines should be thinned out from time to time

    To be successful in the fight against powdery mildew infection, you need to start treatment as early as possible. In the case of vines, this means spraying preventively from the very first shoot in early spring and at regular intervals. You can also use biological sprays, such as plant manure that you have made yourself. In addition, correct planting and care is crucial for the health of the vines. Therefore, pay particular attention to these tips:

    • Be sure to keep the planting distance open!
    • Do not place vines directly in front of a wall, but keep a minimum distance of one meter.
    • Don't let the shoots and leaves grow too densely, but train the vines to be airy.
    • This works best on a trellis.
    • Protect the leaves from rain and moisture.
    • Never pour wine from above, always pour it directly onto the floor.
    • Water in the morning if possible, never in the evening!
    • Herbs placed between the vines, e.g. B. basil, chervil or chives also keep mildew away.
    • Support the plants' immune system with the regular administration of field horsetail manure.
    • Pull weeds regularly.

    It is also extremely important to pay attention to a balanced fertilization. An excessive supply of nitrogen in particular acts practically like a breeding ground for powdery mildew fungi.

    Plant resistant grape varieties

    youtube

    However, the best way to combat powdery mildew is to grow more or less resistant grape varieties. "Resistant" does not mean that the corresponding variety is completely insensitive to the pathogens, but rather that an infection is less likely. In recent years, the "Regent" variety in particular has stood out in this respect, which is why it is still recommended. However, this variety is now losing its resistance, which is why you should perhaps choose one of the following varieties:

    • Muscaris
    • Hospitaller
    • helios
    • Cabernet Blanc (white)
    • Muscat Blue (red)
    • baron (red)
    • Villaris (white)
    • Reberger (red)
    • Felicia (white)

    Newer American grape varieties are also often resistant to powdery mildew, but are less suitable for cultivation in Germany due to the different climate.

    frequently asked Questions

    Can you eat grapes infected with powdery mildew?

    As long as only the leaves or shoots of the vine are infected with powdery mildew, the grapes remain edible. It only becomes problematic when the grapes themselves are covered with the mushrooms: in this case, they are no longer suitable for fresh consumption or for further processing. This is not only due to the unpleasantly changed aroma, but also because the grapes dry up and get a hard, leathery skin.

    How harmful is powdery mildew to humans?

    In fact, powdery mildew is also toxic to humans. The fungus is particularly dangerous for people who suffer from an allergy to penicillin, for example - they can suffer from severe allergic reactions if they eat parts of the plant that are infected with powdery mildew. For this reason alone, you should refrain from eating grapes that are affected by powdery mildew.

    tips

    Some beneficial insects, such as sawflies or ladybugs, actually eat powdery mildew, so you can use them to help fight the disease in the garden.

    Help the development of the site, sharing the article with friends!

Category:

Vegetable garden