Rose rust is one of the most common rose diseases. The fungal disease is unmistakable due to the characteristic orange to brownish pustules on the undersides of the leaves. In this article we explain how to treat the infection correctly and how to prevent it effectively in the future.

Above all, rose rust impairs the beautiful appearance of the roses

Table of Contents

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  1. the essentials in brief
  2. What is rose rust?
  3. recognize rose rust
  4. Combat rose rust
  5. Effective prevention against rose rust
  6. frequently asked Questions

    7. the essentials in brief

    • Rose rust is initially identified by orange pustules on the undersides of leaves. These later turn black.
    • The spores overwinter on leaves, shoots and on the ground. In the following year, without countermeasures, renewed infection is likely.
    • Remove infested plant parts and dispose of them with household or organic waste.
    • Spray with field horsetail broth to treat and prevent it.

    What is rose rust?

    Rose rust is a typical rose disease caused by fungi of the species Phragmidium mucronatum or Phragmidium tuberculatum. These fungi remain permanently on a plant once colonized and overwinter on it. This means that unless you fight an infestation, it can return year after year.

    Like all rust fungi, rose rust is stubborn. Towards the end of summer, numerous permanent spores form in the now black pustules, which are mainly on the leaves and woody shoots and spend the winter there. Here they remain dormant until around the end of March, when the new leaves sprout and infect them too. In addition, the fungal spores are so fine that the wind disperses them, further spreading the disease. With the autumn fall leaves, they also reach the ground. Rose rust begins to germinate when the weather is rather damp and very quickly forms many spore deposits.

    Recognize rose rust in good time

    Rose rust begins on the underside of the leaf

    In the early stages, rose rust can only be seen if you look very closely and especially at the underside of the leaves. Nothing can be seen from above for a long time and the rose looks perfectly healthy, while numerous tiny orange bumps have long since formed on the underside of the leaves. Light to blackish leaf discoloration can only be seen from above as the process progresses and when the summer camps turn black in late summer.

    damage and symptoms

    You can recognize an infestation with rose rust by these symptoms:

    • Orange to orange-brownish elevations, about the size of a pin, mostly on the underside of the leaves
    • can occasionally also appear on the upper side of the leaves and on the shoots
    • often (usually only later) orange spots on the upper side of the leaves
    • Elevations and leaf coloring turn blackish-brown in late summer

    Severely affected leaves may turn yellow and fall off.

    How to distinguish blackspot and rose rust

    Rose rust and blackspot are both fungal plant diseases that are common to roses and are sometimes confused with one another. In contrast to the rust disease, however, blackspot is a dangerous infection that can quickly lead to the death of the rose. You distinguish the disease from rose rust by these characteristics:

    • Leaf spots are yellowish, brownish or black
    • at the beginning isolated and very small stains
    • typically have irregular and fringed edges
    • grow very quickly in humid weather
    • morning dew also promotes growth
    • Spots grow larger quickly
    • Leaf yellows and falls off

    To prevent black spot (and other fungal diseases), you should regularly spray freshly made field horsetail broth when the leaves begin to sprout. A cycle of 14 days is ideal. Diluted whole milk or sodium hydrogen carbonate are also very suitable for prevention. On the market you can get agents based on copper or sulfur for this purpose.

    Follow

    Rose rust is relatively harmless

    "If you want roses to stay healthy and bloom beautifully, you need to prune them every year."

    Compared to other fungal diseases, rose rust is a harmless infection that initially only has a negative impact on the appearance. It only becomes problematic with a very severe infestation or if this occurs again and again over the years. In this case, there can be a complete loss of leaves, and the rose is also weakened. This weakening in turn manifests itself in reduced growth and in a lower willingness to bloom - the rose produces fewer flowers or even no flowers at all. The rose bush very rarely dies as a result of the heavy infestation.

    digression

    What other reasons are there for the non-flowering of roses?

    Roses are quite capricious flowers and generally only bloom when they feel good. If only a few or no flowers are formed, this can have various causes. In addition to diseases such as rose rust, a pest infestation (e.g. with aphids), an unsuitable location, incorrect care or a wrong cut - in which the bud-forming shoots are cut off - also lead to a reluctance to flower. Furthermore, roses do not tolerate damp weather or soil that is too wet and react to this with reduced flower development.

    Successfully combat rose rust - methods and means

    If the weather is good, the fungal spores spread very quickly and infect other roses in the garden. In order to avoid further spread and infection, you should take countermeasures quickly. Especially in the early stages, you can do without fungicides for rose rust, as various home remedies can be used just as well. In this section we explain what these are and what other treatment options you have.

    Proven home remedies

    Spraying with field horsetail broth is very effective against rose rust and other fungal diseases (e.g. powdery mildew). You can spray them every 14 days as a preventive measure from the beginning of budding in mid to the end of March or in the event of a specific infection. For a preventive treatment, dilute the decoction in a ratio of 1:5 with soft water, for a fungus treatment, on the other hand, spray it undiluted.

    Horsetail Broth Recipe:

    • collect fresh field horsetail
    • Chop 500 grams very finely, then the ingredients will wash out better
    • alternatively use 150 grams of dried herb
    • steep in five liters of soft water for 24 hours
    • then simmer for half an hour at low temperature
    • let cool and strain

    Fill the fresh brew into a spray container and spray your roses with it. Treat the undersides of the leaves in particular, they must be dripping wet. It is best to spray early in the morning on a warm day to allow the moisture to dry quickly.

    You can also make fern or garlic broth in the same way, which are also good for combating or preventing rose rust. For the fern broth you should collect bracken or male fern, both of which often grow in a carpet-like manner in damp mixed forests. For the garlic broth, use whole cloves of garlic with the skin and leaves, not just individual cloves.

    tips

    Baking soda also helps against fungal diseases such as rose rust and blackspot. Mix two teaspoons of pure baking soda (e.g. baking soda or baking soda, but no baking soda!) with a liter of warm water and use the mixture as a spray. You can also sharpen it preventively. The addition of cooking oil and detergent (as often described), however, is not necessary.

    Biological and chemical sprays

    The use of fungicides is generally not recommended

    Various fungicides are commercially available that can be used in the event of an acute infestation with rose rust. But be careful: Do not use these remedies repeatedly and over a period of weeks, otherwise the fungi will become resistant to them. Therefore, change the group of active ingredients regularly. These sprays are approved for hobby gardens:

    • Compo Ortiva (contains azoxystrobin)
    • Fungisan Rose and Vegetable Mushroom Free (contains Azoxystrobin)
    • Compo Duaxo (contains difenoconazole)
    • Celaflor Rosen-fungusfrei Saprol (contains triticonazole)

    You must not inject the first two and the last two products one after the other, as these belong to the same group of active ingredients. Also, you should only carry out the treatment with fungicides until the beginning of flowering, since the ingredients affect bees and other beneficial insects.

    In any case, you should think twice about using fungicides and only use them if there are no alternatives. These agents have significant side effects not only on the ecological balance - they are simply highly toxic and should therefore be avoided if possible. On the other hand, it is better (although not optimal) to use sprays such as copper or sulfur. These are also approved in organic farming against a large number of fungal plant diseases.

    Further measures

    If you discover the characteristic pustules on the rose petals, you should act immediately. The first steps to be taken are:

    • Remove any affected leaves.
    • Cut back the infected shoots and branches.
    • Pick up fallen leaves from the ground.
    • If the infestation is severe, remove the top layer of soil.
    • Fungal spores can also hide here.

    All plant parts and the removed soil belong in the household or organic waste. In any case, do not leave them in the garden, as the fungal spores will spread further from here. Further treatment takes place afterwards.

    Effective prevention against rose rust

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    Careful prevention is better than applying toxic pesticides in the house and hobby garden anyway, so that rose rust does not appear in the first place. These measures will help you to prevent an infection in the first place:

    • location: Roses do well in sunny, airy locations with humus-rich, loose soil.
    • planting distance: When planting, make sure there is sufficient planting distance, as fungal diseases can spread more easily in plantings that are too narrow.
    • Regular pruning: Regular pruning makes sense for the same reason, because moisture dries off faster in loose, airy crowns and bushes. This reduces the risk of infection.
    • spring pruning: Roses are generally pruned at forsythia bloom. Take this opportunity to remove infected shoots and twigs so that the new leaves don't come into contact with the spores in the first place.
    • fertilization: Highly nitrogenous fertilization softens the plant material and makes it susceptible to the invasion of fungi and other pathogens. Therefore, fertilize in a balanced way and save with nitrogen. Potassium, on the other hand, is good because this nutrient strengthens the cell walls.
    • pour: In dry periods - especially in spring and summer - you should keep the soil evenly moist, as drought weakens the rose. Always water directly onto the soil and never over the leaves - wet foliage is a source of infection!
    • mulching: In the fall, mulch the root disc with wood chips and horn shavings (€32.93) or humus-rich potting soil. This prevents fungal spores on the ground from getting onto the plant.
    • leaves: Remove and discard fall foliage.

    Infected clippings and fallen leaves do not belong in the compost, as the temperatures here usually do not get high enough to reliably kill the fungal spores.

    Plant resistant rose varieties

    If you want to play it safe and avoid fungal diseases, plant so-called ADR roses in your garden. These are modern breeds that have been tested over the years for their resistance to the common rose diseases rose rust, powdery mildew and blackspot and have proven to be particularly resilient. But be careful: Resistant does not mean that these roses cannot get fungal diseases at all - of course they can still do that, even if infection is less likely.

    In addition to the ADR varieties, you should therefore rely on preventive measures. An optimal location as well as a balanced fertilization and water supply help to avoid a fungal infection. Of course, an outbreak can still occur in wet summers: avoid using fungicides in such a case, as the fungi become resistant to them, change their genetic make-up and therefore the ADR varieties are no longer immune to their attacks. Their genome does not adapt to the modified fungal pathogens.

    frequently asked Questions

    Are there other plants that are affected by rose rust?

    Rose rust only affects real roses

    The fungal disease rose rust only affects real roses, no other plant species. However, there are a whole range of other rust fungi, each of which has specialized on certain host plants. They all have the typical pustules in common, and the different varieties are also similar in terms of further damage and the measures to combat them.

    What other diseases are common on roses?

    Roses are generally susceptible to various fungal diseases. In addition to rose rust, they are often attacked by powdery mildew and sooty mildew, with some varieties being less sensitive to the infections mentioned than others. Anyone who plants ADR roses chooses proven and resistant varieties.

    Why do roses get rose rust in the first place?

    Like so many fungal diseases, rose rust is airborne. The microscopic spores reach the plants with the wind and spread over the roses within a very short time. Sometimes the disease is also transmitted by newly purchased roses planted in the border if they were already diseased when they were bought. In the early stages of the disease, an infestation cannot always be detected.

    Is rose rust also dangerous for humans?

    Rose rust is annoying for humans, but completely harmless. It is a pure plant disease that affects neither humans nor animals. However, you should refrain from eating roses infested with fungi - the fungal toxins they contain could cause symptoms such as a skin rash, at least in allergy sufferers.

    tips

    You should therefore check your roses for any changes from the moment they sprout - approximately every week. In this way, you not only recognize rose rust, but also other diseases and pest infestations in good time.

Category:

Vegetable garden