Recognize and treat rose rust

the essentials in brief

• Rose rust is initially identified by orange-colored pustules on the underside of the leaves. These only turn black later.
• The spores overwinter on leaves, shoots and on the ground. Unless countermeasures are taken, a new infection is likely in the following year.
• Remove infected parts of the plant and dispose of them with household or organic waste.
• Spray with horsetail broth for treatment and prevention.

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 once colonized plant and overwinter on it. This means that if you don't control an infestation, it can come back every year.

also read

• Recognize and treat rose rust
• Powdery mildew, star soot, rose rust - the most common leaf diseases on roses
• Recognize and fight rose diseases

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 located on the leaves and on woody shoots and spend the winter there. Here they rest until around the end of March, when the new leaves sprout, and they also infect them. In addition, the fungal spores are so fine that the wind spreads them and thus ensures the further spread of the disease. They also hit the ground with the autumn leaves. Rose rust begins to germinate in rather damp weather and very quickly forms many spore beds.

Recognize rose rust in good time

In the early stages, rose rust can only be seen if you look very carefully and, above all, examine the undersides of the leaves. For a long time nothing can be seen from above and the rose looks completely healthy, while numerous tiny orange-colored bumps have long formed on the underside of the leaves. Only in the further course and when the summer camps turn black in late summer, light to blackish leaf discolorations can also be seen from above.

Damage and symptoms

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

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

Heavily infested leaves can turn yellow and fall off.

How to distinguish between soot and rose rust

Rose rust and star soot are both fungal plant diseases that often occur in roses and are sometimes confused with one another. In contrast to the rust disease, star soot is a dangerous infection that can quickly lead to the death of the rose. You distinguish the disease from rose rust by these features:

• Leaf spots are yellowish, brownish or black
• isolated and very small spots at the beginning
• typically have an irregular and fringed edge
• grow very quickly in damp weather
• Morning dew also favors growth
• Spots get bigger quickly
• Leaf yellows and falls off

In order to prevent star soot (and other fungal diseases), you should regularly spray freshly made horsetail broth when the leaves begin to shoot. A cycle of 14 days is ideal. Diluted whole milk or sodium hydrogen carbonate are also very suitable for prevention. For this purpose, you can find products made on the market based on copper or sulfur.

consequences

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

Compared to other fungal diseases, rose rust is a harmless infection that initially only has negative effects on the appearance. It only becomes problematic if the infestation is very severe or if it occurs repeatedly over the years. In this case, the leaves can be completely lost and the rose is weakened. This weakening, in turn, manifests itself in reduced growth and less flowering - the rose produces fewer or even no flowers at all. The rose bush very rarely dies as a result of the severe infestation.

Digression

What other reasons are there for the roses not blooming?

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

Fighting rose rust successfully - methods and means

When the weather is favorable, the fungal spores spread very quickly and attack 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 with rose rust, as various home remedies can be used just as well. In this section we will explain which these are and which treatment options you still have.

Proven home remedies

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

Recipe for horsetail broth:

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

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

You can also make fern or garlic broth in the same way, which are also great for combating or preventing rose rust. For the fern broth you should collect eagle or worm fern, both often grow like carpets in damp mixed forests. For the garlic broth, use whole cloves of garlic including the skin and leaves, not just individual cloves.

Tips

Soda also helps against fungal diseases such as rose rust and star soot. Mix two teaspoons of pure baking soda (e.g. emperor soda or baking soda, but no baking powder!) With one liter of warm water and use the mixture as a spray. You can also tip it preventively. However, it is not necessary to add cooking oil and detergent (as often described).

Biological and chemical sprays

Various fungicides are commercially available which can be used in the event of an acute attack with rose rust. But be careful: Do not use these agents repeatedly and over and over for weeks, otherwise the fungi will become resistant to them. You should therefore change the active ingredient group regularly. These sprays are approved for the hobby garden:

• Compo Ortiva (contains azoxystrobin)
• Fungisan rose and vegetable mushroom free (contains azoxystrobin)
• Compo Duaxo (contains difenoconazole)
• Celaflor Rose Mushroom Free Saprol (contains triticonazole)

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

In any case, you should carefully consider the use of fungicides and only use them when 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. However, it is better (if not optimal) to use sprays such as copper or sulfur. These are also approved in organic farming to combat 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 infected leaves.
• Cut back the infected shoots and twigs.
• 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 as well as the soil removed belong in the household or organic waste. Under no circumstances should you leave them in the garden, as this is where the fungal spores spread further. Further treatment only takes place afterwards.

Effective prevention against rose rust

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In any case, careful prevention is better than applying toxic pesticides in the home and hobby garden so that rose rust does not appear in the first place. These measures will help you prevent infection in the first place:

• Location : Roses feel comfortable in sunny, airy locations with humus-rich, loose soils.
• Plant spacing : Make sure that there is sufficient plant spacing when planting, as fungal diseases can spread more easily in too narrow plantations.
• Regular pruning : For the same reason, regular pruning makes sense, because moisture dries faster in loose, airy crowns and bushes. This will reduce the risk of infection.
• Spring pruning : roses are generally pruned for forsythia bloom. Take this opportunity to remove infected shoots and twigs so that the new leaves do not even come into contact with the spores.
• Fertilization : A highly nitrogen-based fertilization makes the plant material soft and thus susceptible to the penetration of fungal and other pathogens. So fertilize in a balanced way and save with nitrogen. Potassium, on the other hand, is good because this nutrient strengthens the cell walls.
• Watering : In dry seasons - especially in spring and summer - you should keep the soil evenly moist, as drought weakens the rose. Always water directly on the ground and never over the leaves - damp leaves are a source of infection!
• Mulching : In autumn, mulch the root disc with wood chips and horn shavings (€ 6.39 at Amazon *) or humus-rich potting soil. This will prevent fungal spores on the ground from getting onto the plant after all.
• Foliage : Remove and dispose of autumn leaves.

Infected cuttings and fallen leaves do not belong on the compost, as the temperatures here are usually not high enough to reliably kill the fungal spores.

Plant resistant rose varieties

If you want to be on the safe side and avoid fungal diseases, plant so-called ADR roses in the garden. These are modern breeds that have been tested for years for their resistance to the common rose diseases rose rust, powdery mildew and star soot and have proven to be particularly resistant. But be careful: Resistant does not mean that these roses cannot develop fungal diseases at all - of course they can anyway, even if an infection is less likely.

So in addition to the ADR varieties, you should take preventative 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 damp summers: Avoid using fungicides with such an outbreak, as the fungi become resistant to them, change their genetic makeup and therefore the ADR varieties are no longer immune to attack. Their genetic makeup does not adapt to the changed fungal pathogens.

frequently asked Questions

Are there any other plants that are attacked by rose rust?

The fungal disease rose rust only affects real roses, no other plant species. However, there are a number of other rust fungi, each specializing in certain host plants. They all have the typical pustules in common, and the different varieties are similar in terms of the further damage and the measures to be taken to control them.

Which diseases are still common in roses?

Roses are generally prone to various fungal diseases. In addition to rose rust, they are often attacked by powdery mildew and star soot, although some varieties are less sensitive to the infections mentioned than others. Those who plant ADR roses choose proven and resistant varieties.

Why do roses get rose rust at all?

Like so many fungal diseases, rose rust is also transmitted through the air. The microscopic spores reach the plants with the wind and distribute themselves on the roses within a very short time. Sometimes the disease is also transmitted through newly bought roses and planted in the borders if they were sick when they were bought. In the early stages of the disease, an infestation cannot always be determined.

Is rose rust also dangerous for humans?

Rose rust is annoying for humans, but completely harmless. It is a pure plant disease that does not affect humans or animals. However, you should refrain from eating roses that have been infected with fungi - the fungus poisons they contain could cause symptoms such as a rash, at least in allergy sufferers.

Tips

You should therefore check your roses for any changes as soon as they emerge - e.g. on a weekly basis. In this way you not only recognize rose rust, but also other diseases and pests in good time.