How to Treat and Prevent Black Spots on Roses

Black Spots on Roses

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Prevent Black Spots on Roses

Black spot is a fungal disease (Diplocarpon rosae) that affects roses. The fungus develops as black spots on the leaves, which eventually cause the leaves to turn yellow and fall off. Not only does it look ugly, but it can also seriously weaken the rose plant. Black spot thrives in cold, humid climates, while extreme summer heat limits the disease.

What does the black dot do?

The black spot appears as slightly circular black spots on the leaves. It usually appears on top of the leaves, but it can also develop underneath. The outer edges of the black circles are toothed or pinnate and are generally surrounded by a yellow ring.
The spots usually start on the lower leaves and move upward. They can appear as soon as the leaves open. These points can be expanded and eventually merged. Affected leaves usually fall off the plants, and if left unchecked, the entire plant can collapse.
The fungus can also infect young stems and cause purple or black blisters on the stems, and the flowers can also have red spots. Infected plants produce fewer buds and are leafless, the plants are stressed and prone to more problems.

Black Spots on Roses

Environmental proof of the problem

Although infected leaves cannot be cured, black spots can be avoided. Existing spores hibernate on infected leaves and stems and await favorable conditions. The spores germinate in the spring and are transferred to the plant by spraying water. The spores must be bathed continuously for 7 hours before infection occurs. The spores develop fertile bodies called avulsions in black lesions. They produce spores that inject new tissue and spread disease.

Provides the plant with optimal growth conditions.

To prevent plant diseases, a healthy and vigorous plant is less prone to problems. Roses prefer a sunny location with well-drained soil and regular weekly watering. Plant the roses in a spot where you can bask in the morning sun, which helps dry out the damp leaves. Every day all the sun is the best.

Good airflow

Provides good air circulation around and through rose plants. Don't plant roses too close to other plants. If the plant becomes too dense and air cannot get through, gaps can be cut between the stems. Having good air circulation and making sure the reeds don't cross makes it difficult for the black spot to spread.

Adequate watering

Avoid wetting the leaves during watering. You can't do much in the rain, but avoid splashes and focus the water directly on the roots of the plant.


Remove infected leaves and clean them thoroughly each fall. Remove and discard any remaining leaves when you may be sleeping in late winter/spring. The spores can remain on leaves and stems and re-infect under favorable conditions. Ten days after the first symptoms, the disease began to spread. The spores spread in the water. Remove the stems that show signs of infection. Prune 15 to 8 inches during infection and prune only in dry weather. Between sections, disinfect the section with a 10% alcohol or bleach solution. Discard infected leaves and sugarcane: Do not compost because spores can infect the plants again. Also, clean the fallen leaves and remove them properly.

Black Spots on Roses


Apply a thick layer of mulch around the plants. The shed prevents the soil from being sprayed on the plant, and if there are spores in the soil, it prevents the fungus from spreading.

Topical sprays for treatment and prevention.

There are commercial and homemade DIY solutions that you can use to prevent the spread of blackheads. Treatment may seem long; It is an irritating problem. And if the blackheads reappear after treating the plants, they may need to be sprayed weekly, starting in the spring.

  • Baking powder: dissolve 1 teaspoon of yeast in 1 liter of warm water. Add up to 1 teaspoon of liquid soap. Spray the leaves well. This mixture acts preventively. It also offers some protection against powdery mildew.
  • Bordeaux mixture: it is a fungicide that contains copper sulfate and hydrated lime. It can be used as a powder or mixed with water and sprayed. The Bordeaux mixture also repels pests, but it can burn plant leaves. It is generally used as a preventive measure in spring before the plants are exhausted.
  • Insecticidal soaps with added fungicide: You can use an organic fungicide, which is usually sulfur, which is added to regular insecticidal soap. The soap covers the leaves and helps the fungicide adhere to the plant.
  • Neem Oil: Neem is a biological fungicide and pesticide obtained from the seeds of the neem tree. Get into the installation system so you don't have to worry about siding or recycling after it rains. However, it can burn plant leaves in the scorching sun. Do not use neem oil within two weeks of using a product that contains sulfur.
  • Sulfur: Sulfur prevents fungal diseases. It is also used to control various pest insects. Sulfur is a finely ground powder. If you prefer to spray, look for one that is marked wettable so it mixes with the water.

Black Spots on Roses


It can be easily toxic to humans and other animals. Protective clothing should be worn when spraying. It can also attack metals, so use a plastic syringe. And it can burn plant leaves in hot weather.

Plant resistant varieties

Roses are often labeled hardy, very hardy on the down. If you are looking for resistance to black stains, you can also look for a rose that is resistant to rust and mold. Rugosa, a new rose bush and canopy, and many Canadian scout roses such as 'John Cabot' and 'William Baffin' show good persistence.

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Black Spots on Roses

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