Status: 07.08.2023 5:20 p.m
Blackspot is one of the most common fungal diseases in roses. If the plants are infected, the leaves develop black spots and turn yellow over time. How to fight the infestation?
A location that is too damp and shady favors rose diseases such as rose rust, powdery mildew and black spot (Diplocarpon rosae). In the so-called black spot disease, black-brown spots that diverge in a star shape initially form before the rose petals turn yellow and finally fall off. This weakens the plants and prevents, among other things, the formation of new flowers.
What helps against star soot?
Blackspot overwinters mainly on fallen leaves and can survive for several years even at minus 20 degrees. So always pick up fallen leaves quickly. In the case of infested roses, blackspot can be recognized from around May and should then be dealt with immediately. Infected leaves and shoots must be meticulously removed and disposed of with household waste to prevent the blackspot from spreading. Other plants, such as oleander and laurel, can also be affected by the fungus.
In stubborn cases, treatment with chemical pesticides (fungicides) is necessary. Always follow the manufacturer’s instructions for use exactly.
Prevent blackspot on roses
Always disinfect the rose scissors so that pathogens are not transferred to other plants.
Anyone who plants roses in their garden should make sure from the start that the location is not too damp, so that fungal diseases such as blackspot cannot develop in the first place. It is therefore advisable to ensure that there is sufficient distance between the individual roses when setting them. Regular pruning also ensures good ventilation. When watering, only water the roots, this prevents unwanted moisture on other parts of the plant.
A purely biological remedy can also be used to prevent this – a decoction of field horsetail, with which the roses are sprayed in spring and summer. A high-potassium, low-nitrogen fertilizer provides the rose with a good supply of nutrients, making it less susceptible to diseases.
Choose hardy rose varieties
There are now some breeds that are resistant to blackspot, such as “Dortmund”, “Angela”, “Heidetraum” or “Sommerwind”. When buying, it is best to pay attention to the so-called ADR seal, which distinguishes varieties that are particularly resistant to diseases.
Further information
Prevent, recognize, fight: the most common rose diseases and rose pests and what you can do about them. more
The rose is considered the queen of flowers. Not only does it look gorgeous, it also requires special care. more
Powdery mildew is a typical rose disease. If the roses are affected, a home remedy made from milk will help. more
Roses with curled leaves are infested with scroll wasps. The leaves should be better cut off. more
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