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Sooty mildew: We show you how to recognize black spot disease on roses, how to prevent it and what methods you can use to combat the fungus.

Black spots and yellowing indicate blackspot

You can recognize blackspot by these symptoms

Black spot is a common fungal disease that only affects roses (Rosa). In most cases, the infestation first occurs on the leaves near the ground and, in unfavorable cases, spreads from there to the entire plant. The first symptoms can appear as early as May. The disease can be recognized by small, star-shaped spots with a blurred edge. The spots are black-brown and can reach a size of 3 cm. As the disease progresses, the leaves become so weak that the foliage yellows and falls off. If the summer is characterized by many wet and humid weather periods, the rose can lose all its leaf splendor.

Advanced infestation of blackspot causes leaf yellowing

Blackspot Pathogen

Black spot (sometimes called black spot) is caused by a fungus called Diplocarpon rosae. It overwinters in the form of spores in the soil and especially on old, infected leaves and shoots. But plants can also be infected by the wind. The fungus spreads particularly quickly in wet weather with temperatures above 15 °C and high humidity.

Preventive measures

First of all, old infested leaves and parts of plants must be disposed of with the residual waste. The spores are not decomposed in the compost and can infect your roses again from there. So that the fungal spores cannot gain a foothold on the rose, it is extremely important to dry the leaves quickly. A sunny and airy location is very important for this. Splashing water should also be avoided when watering and a strong nitrogen fertilization is also very unfavourable. Furthermore, many gardeners recommend regular spraying (once a week) with horsetail tea. The silicic acid contained there strengthens the cell walls of the leaves and the fungus hardly has the opportunity to trigger an infection.

Leaves affected by blackspot should be removed quickly

How to combat blackspot effectively

Fighting soot is often unavoidable. Because of the disease, the flowers fail to appear or only appear in small numbers and the frost sensitivity of the entire rose is also increased. In addition, there is a high probability that the disease will reappear next year. To put an end to the infestation, we recommend Fungisan Rose and Vegetable Fungus Free. If you use it repeatedly, the soot dew will no longer stand a chance.

The following products have proven themselves in our garden:

  • COMPO Duaxo Rosen Pilz-frei: Fully systemic pesticide with depot effect; stops further spread; Protects roses, ornamental plants and herbs
  • NEUDORFF Fungisan rose and vegetable mushroom-free: plant protection product that is gentle on beneficial insects and not harmful to bees with a very good long-term effect
  • COMPO Duaxo Universal Fungus-free: Fully systemic fungicide spray; Reliably protects against new infestations and stops the spread

Unfortunately, roses are often attacked by diseases and pests. Therefore, we present the most common rose diseases, their symptoms and how you can combat them.

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