It is not without reason that the rose is also referred to by many as the "Queen of Flowers" and should not be missing in any ornamental garden. Unfortunately, the beauties are very susceptible to diseases, especially fungal infections such as powdery mildew. Read what you can do against this common pathogen.

Roses are very susceptible to powdery mildew

Table of Contents

Show all
  1. the essentials in brief
  2. Powdery mildew or downy mildew?
  3. Combat powdery mildew on roses
  4. prevent powdery mildew
  5. Resistant rose varieties
  6. frequently asked Questions

    7. the essentials in brief

    • Powdery mildew is a fair-weather fungus, while downy mildew is a bad-weather fungus
    • There are numerous good home remedies for mildew, including whole milk, horsetail manure, tansy tea, garlic stock, essential oils such as oregano
    • Professional pruning and good care prevent mildew infestation

    Powdery mildew or downy mildew on roses?

    No question: as soon as the leaves and shoots of your roses show the first signs of an infestation with powdery mildew, you naturally want to treat the disease immediately. However, it is important to first make an accurate diagnosis. Powdery mildew is by no means the same as powdery mildew, because there are a whole range of different fungal pathogens. Depending on whether it is powdery mildew or downy mildew, you must also select the appropriate treatment. What helps against powdery mildew does not necessarily work against the wrong one.

    The table below shows you how best to distinguish between the different types of powdery mildew and what remedies can help.

    powdery mildew Wrong mildew
    pathogen Ascomycota (Erysiphaceae) Egg mushrooms (Peronosporaceae)
    This is how you recognize an infestation white, mealy and wipeable coating or spots on leaf tops, stems and shoot tips, may also appear on flowers and buds white to gray coating on the underside of the leaf, can also be velvety brown
    damage in the further course of the disease Plant parts turn brown, dry up and fall off. Plant parts turn brown, yellow or purple.
    Occurs under these conditions Fair weather fungus: occurs in dry weather with temperatures between 20 and 25 °C, morning dew is dangerous, transmission by insects and wind is possible Bad weather fungus: occurs in humid weather with temperatures between 15 and 20 °C or in high humidity (e.g. in the greenhouse).
    Best Antidote Spray with horsetail extract, garlic Spray with tansy infusion, oregano, savory

    Causes of Powdery Mildew

    Incorrect care or changes in the weather favor powdery mildew

    Powdery mildew occurs mainly as a result of severe weather changes (mainly in spring) or because the roses have not been properly cared for. Above all, planting too close together, incorrect watering over the leaves and nitrogen-rich fertilization promote fungal diseases. Check your rose plants regularly for signs of an infestation so that you can act immediately when the first symptoms appear. Powdery mildew spreads very quickly and is more difficult to combat the more pronounced the symptoms are.

    Powdery mildew on roses - what to do?

    You can find out how to plant and care for roses properly and thus keep mildew and other rose diseases away in this informative article:

    Video:youtube

    You can only protect yourself against powdery mildew on roses by taking suitable precautionary measures, which we will present to you later in this text. If these don't help, try some proven home remedies first. These include a whole milk-water mix or a baking soda-based spray, both of which are slightly acidic and inhibit the growth of the fungus. In addition, there are other very good sprays that you can make from ingredients you have collected yourself.

    However, cutting back infested parts of the plant is fundamental to the success of the measures. Already discolored leaves and shoots no longer get a healthy color anyway, which is why only generous pruning helps in the event of a severe infestation. Slightly affected roses, on the other hand, can be treated by wiping the affected leaves with a milk mixture, providing the plants with a tonic and, if necessary, improving the site conditions and care.

    Known home remedies for powdery mildew on roses

    There are many good home remedies for powdery mildew on roses

    The two home remedies listed here are proven classics that help against both powdery mildew and downy mildew. It is important not to carry out the spraying once, but several times at intervals of a few days over a period of at least two to three weeks. Also make sure that you can dry rose petals and shoots quickly afterwards. Therefore, carry out the spraying preferably in the late morning and in dry weather.

    Mixture of whole milk and water for spraying

    The well-known milk-water mixture, which you can use to treat your roses as a preventive measure from the start of the growing season, has proven its worth, especially in the case of an initial to light infestation with powdery mildew. The recipe is as follows:

    1. If possible, use untreated whole milk (at least 3.5 percent fat).
    2. Alternatively, you can also use buttermilk.
    3. Mix the milk with boiled and cooled water in a ratio of 1:9.
    4. It is best to use rainwater or well-stale tap water.
    5. Pour the mixture into a clean and sanitized spray bottle.
    6. Spray the roses affected with powdery mildew so heavily that the spray drips from the leaves and shoots.
    7. Be sure to treat the undersides of the leaves.
    8. Repeat the treatment several times a week.

    baking powder mixture

    Baking powder works even better than spraying with a mixture of milk and water. However, do not choose just any baking powder, choose one with baking soda. Mix one packet with two liters of water and 20 milliliters of neutral cooking oil (e.g. rapeseed or sunflower oil) and pour the mixture into a spray bottle. Treat the parts of the plant affected by powdery mildew several times a week.

    Make your own sprays against powdery mildew on roses

    In general, chemical sprays are only very rarely necessary in the hobby garden. After all, there are enough effective substances in nature that can be produced inexpensively and easily by yourself. If you prefer to buy a ready-made product, you can use the "fungus-free" biological preparation.

    Horsetail against powdery mildew

    Field horsetail can be used to make effective liquid manure against powdery mildew

    Field horsetail grows almost everywhere and is often regarded as a weed and plucked out. Manure made from the herb not only has a very stimulating effect on roses and is very good at preventing infection with powdery mildew. You can use horsetail broth - diluted with water in a ratio of 1:10 - both as a prevention and to treat the early stages of powdery mildew. The effect is based on the mineral salts it contains, such as silica, potassium and calcium, which make roses and other plants more resistant to powdery mildew.

    Recipe for horsetail manure

    1. Gather a kilogram of field horsetail without roots. Alternatively, you can also use horsetail.
    2. Chop up the plant parts.
    3. Place the plant material in a plastic bucket.
    4. Pour in ten liters of cold water.
    5. Rainwater is best.
    6. Add a handful of bedrock meal.
    7. Stir well.
    8. Leave the mixture covered with a burlap cloth or piece of chicken wire ($14.99) for about 14 days.
    9. Stir twice a day.

    The liquid manure is ready as soon as no more bubbles rise. Now you can filter the liquid and fill it in canisters. Between April and August, spray your roses dripping with the product about every eight to ten days.

    Garlic against powdery mildew

    A garlic extract has also proven itself as a tried and tested remedy against powdery mildew. Spray the affected parts of the plant with the agent diluted with water in a ratio of 1:10 or 1:20 (depending on the severity of the infestation), preferably in the evening. Repeat the application regularly.

    Garlic extract recipe

    1. Mince 100 grams of garlic with the peel.
    2. Mix the garlic with three tablespoons of canola oil.
    3. Leave the mixture covered for 24 hours.
    4. Now crush the garlic and strain out the liquid.
    5. Add a tablespoon of liquid dish soap.
    6. Mix well.
    7. Finally, pour the mixture with a liter of water.

    Refrigerated and protected from the sun, this preparation will keep for about three weeks.

    Tansy against downy mildew

    Tansy flowers are an effective natural remedy for powdery mildew

    The intensely yellow flowering tansy - often found in the summer months, especially on the edges of fields and paths - makes a great spray against downy mildew when used as an infusion. To do this, pour 1 liter of hot, but not boiling, water over 100 grams of fresh or 20 grams of dried flowers. Allow the brew to steep until it has cooled to room temperature and then strain it. Dilute the agent in a ratio of 1:5 with water and spray the affected parts of the plant with it.

    tips

    Unlike liquid manure and extracts, infusions do not keep and must be used immediately.

    Oregano or savory against downy mildew

    Hardly known, but also very effective against downy mildew, are extracts from savory or oregano. Both herbs contain essential oils that do not get the fungal pathogens. For the production of such a fungicide you also need extra-fine clay so that the active ingredients stick better to the rose petals.

    Recipe for a fungicide based on savory or oregano

    1. Chop 100 grams of fresh cabbage.
    2. Mix this with a tablespoon of canola oil.
    3. Leave the mixture for 24 hours.
    4. Then carefully strain out the liquid that comes out.
    5. Mix this with three to four drops of liquid dish soap.
    6. Now mix the mixture with 250 milliliters of water.
    7. The liquid should be homogeneous.
    8. Now make a clay-water mixture from a teaspoon of clay and a liter of rainwater.
    9. Pour both liquids into a spray bottle and shake well.

    You can use this spray as needed.

    digression

    Cut roses properly

    Regular pruning makes roses more resistant to powdery mildew. On the one hand, you cut away any overwintering fungal spores with an annual spring pruning, on the other hand, the rose is more airy and therefore less endangered per se. How, how much and when you prune depends on the rose variety and its classification.

    This is an effective way to prevent powdery mildew on roses

    "In order for roses to remain healthy, they absolutely need an optimal location!"

    However, the most effective method against all types of mildew is and remains careful prevention. You should heed the following tips:

    • Roses need a light and airy location.
    • Do not plant them too close together, keep the recommended planting distance.
    • The shrubs also feel most comfortable on a moist and nutrient-rich soil.
    • Keep the rose bed weed-free, as many weeds attract and spread fungal diseases.
    • Mulch the root area of the roses with bark mulch.
    • Always water roses from below and directly onto the ground, never over the leaves!
    • Water preferably in the morning, as watering in the evening promotes the development of fungal diseases.

    Watering in the evening also has another disadvantage, because it attracts the voracious slugs.

    digression

    Plant a protective barrier against powdery mildew

    Some herbs are resistant to powdery mildew, which is why you should plant them in the rose bed: chervil, chives, basil and garlic act as a practical natural protective barrier, as does foxglove, by the way.

    These varieties of roses are resistant to powdery mildew

    The word "resistant" implies that the rose varieties marked in this way cannot contract fungal diseases such as powdery mildew. Of course, this is nonsense, since plants that are marked as particularly robust against pathogens can also be infected - for example, because the site conditions are not right (e.g. the roses are planted too close together) or were incorrectly watered / heavily fertilized. Such conditions will, over time, weaken even inherently hardier strains, making them more vulnerable.

    Weather influences occurrence of rose diseases

    In addition to an unsuitable location or incorrect care, the weather can also trigger fungal diseases - for example, if the year was particularly wet. In a year in which a noticeably large number of mushrooms thrive, powdery mildew mushrooms naturally also feel very comfortable. Nevertheless, it makes sense to plant a rose variety that is resistant to powdery mildew, because it is significantly less susceptible than many other varieties - provided, of course, that the location and care conditions are right.

    Choose hardy ADR roses

    If you want to be on the safe side, choose a so-called ADR rose if possible. These are varieties that have to go through a "rose TÜV" and meet strict criteria before they are awarded the seal of approval. These test criteria include not only external factors such as growth and flowering, but also susceptibility to typical rose diseases or winter hardiness. Basically, ADR roses are very robust and not very susceptible to powdery mildew, but by no means completely immune to disease.

    tips

    ADR roses are a German test seal, which is why most of the new breeds from abroad - such as the famous English roses - are not tested. That doesn't mean they're not robust, though - they just won't be submitted for review.

    frequently asked Questions

    Does baking soda actually help against powdery mildew on roses?

    Baking soda actually works very well against mildew - but only if you buy a variety with baking soda (sodium bicarbonate). However, most baking powders available in Germany contain other leavening agents and are therefore unsuitable for the purpose of combating powdery mildew. Baking soda is often commercially available under names such as baking soda, baking soda, or baking soda.

    Is powdery mildew contagious to other plants?

    Since powdery mildew is a fungus - regardless of whether it is "real" or "fake" - the disease is highly contagious. If a rose is already affected by the fungus lawn, the pathogen spreads from this to other roses and other ornamental and crop plants. For this reason, acting quickly and, if possible, isolating the affected plant is so important. Furthermore, plant parts infected with powdery mildew do not belong in the compost, since the spores survive and infect other plants when the finished compost is spread.

    Is powdery mildew actually poisonous?

    Both powdery mildew and downy mildew are poisonous. People who are allergic to fungi or penicillin are particularly at risk. Contact with the powdery mildew fungus can cause these people to suffer from severe allergic symptoms and even an allergic shock. As an allergy sufferer, you should avoid touching infested plants without protection (gloves, respiratory protection if necessary). Also, do not eat contaminated plant parts, this can lead to problems in the gastrointestinal tract.

    What does mildew tolerant mean?

    Mildew-tolerant rose varieties are less susceptible to infection with the causative fungal pathogens. However, if the conditions are right, the strain in question can still become diseased. Only roses that are resistant to powdery mildew do not suffer from powdery mildew.

    tips

    Remove dried or damaged plant parts as quickly as possible, as these provide the perfect gateway for fungal pathogens. Garden tools used to cut roses (e.g. scissors) should also be cleaned and, if necessary, disinfected before and after each use.

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