Black spots on rose bushes: why do they appear and how to treat them?

black rose spots and their possible causes

The onset of black spots on a rose bush It is a cause for concern. Because, although we are not experts in botany, we know that this is an indication that something is not right with our plant.

So that your rose bushes are beautiful and healthy, we are going to give you some tips to prevent and treat this problem. And we are also going to analyze what these spots indicate to us, because knowing what is happening to our roses is the best way to provide them with the appropriate treatment.

What are black spots on a rose bush?

Why do these spots occur on your flower?

As I'm sure you're already imagining, we can tell you that yes, Those black spots you've seen on your plant are fungi. This is the fungus Marsonia or Diplocarpon rosae, which we commonly know as “black spot.”

Diplocarpon rosae is a fairly common disease in rose bushes, and nowhere in the world are they free from it.

The lesions appear in the form of a black spot (hence the name) with a quite distinctive appearance. Although it is normal for the affected area to be the leaves, In the most serious cases it can spread to the stems, the buds and the flowers.

The spots appear mainly on the upper part of the leaves, but in humid conditions they are also visible at the bottom. They are welts that can be between 1,5 and 13 mm in size. The edges are irregular and the center is darker, and it is not unusual to see a yellowish discoloration around the injured area.

These mushrooms grow, and different stains can merge with each other and give rise to a much larger fungus.

Humidity is the main reason for the appearance of black spots on rose bushes. The fungus Diplocarpon rosae has reproductive structures called pycnids., which are characterized by containing spores. These are dispersed by the effects of wind, rain and irrigation water.

When the spores come into contact with a rose that is susceptible to disease because it is subjected to high humidity conditions, then it penetrates its tissues and infection begins.

Effects of black spots on rose bushes

Fungi cause harmful effects on our plants and, if we do not treat them in time, They can even destroy them.

In this specific case, we can observe the following effects on our rose bushes:

Weakening of leaves

As the disease progresses, the affected leaves have an increasingly weak appearance. They turn yellow and fall prematurely, which limits the plant's ability to photosynthesize efficiently.

Impact on flowering

The premature fall of leaves reduces the amount of energy the plant can allocate to producing buds and flowers. Therefore, a rose bush affected by fungi is a rose bush that blooms much less than one that is completely healthy.

General weakening of the plant

We not only see the harmful effects of the fungus on the leaves and flowering, but also on the plant as a whole. Because the infection causes generalized weakness, making the rose bush more susceptible to other infections and pests, which is a serious risk for its survival.

How to prevent the appearance of Diplocarpon rosae

This is how you can prevent black rose spots

The best way to fight black spot on rose bushes is to adopt preventive measures that stop its development. In this sense, there are several strategies that we can implement:

  • Selection of resistant varieties. Choose varieties of rose bushes that have greater resistance to this type of disease. fungal diseases. Consult the specialists at your garden center to learn more about this topic.
  • Leave space for the plants and prune them. Never place rose bushes or other plants too close to each other. It is advisable to leave a space between them so that air can circulate properly and humidity does not accumulate. Pruning will also help you gain space and improve ventilation.
  • Adequate watering. When you water the rose bush, avoid wetting the leaves. All you have to do is add water to the substrate. In fact, if possible, use a drip irrigation system to prevent fungus from appearing.
  • Remove the affected leaves. As soon as you notice that there is a leaf with a black spot, remove it. With this you reduce the spread of the fungus.
  • Mulching. Apply a layer of mulch around the rose bush to maintain moisture in the soil and reduce splashing water that could contain the fungus.
  • Balanced fertilization. Provide your rose bushes with adequate fertilizer. The healthier the plant is, the better it can defend itself against infections.
  • Preventive fungicides. If you have already had problems with black spots on your rose bush, you can apply preventive fungicides, which contain active ingredients such as chlorothalonil and propiconazole.

How to treat black spots on rose bushes?

This is how you can treat black spots

If you have not been able to prevent the infection and this fungus is doing its thing on your rose bushes, It's time to get to work to apply a healing treatment.

Remove affected leaves

The first thing is to cut corners. Don't be afraid and remove all the affected leaves you see, even if they only have a small spot. If required, do healing pruning.

Also, try not to leave leaves on the ground, to prevent them from infecting other plants that's around.

apply fungicide

Use a specific product for the treatment of black spots, always following the manufacturer's instructions. Remember that by applying more you will not get better or faster results.

If you live in an area with high humidity, it would be advisable to You will apply preventive treatment throughout the year to prevent infection and protect new leaves.

Water properly

Even if the rose bush is infected, it still needs water. In this case, make sure you do not wet the leaves, the less moisture they have, the better.

With a hose or watering can You can apply water only to the lower part of the plant.

Nourish your rose bush

An infected rose bush can survive if we give it the proper treatment. To give it a better chance of doing so, add a little more to the irrigation water. balanced fertilizer that provides an extra dose of nutrients.

Black spots on the rose bush are not a good sign, but you have already seen that we can prevent them and treat them if they appear. Have you had problems with this fungus?

Leave a Comment

Your email address will not be published. Required fields are marked with *



  1. Responsible for the data: Miguel Ángel Gatón
  2. Purpose of the data: Control SPAM, comment management.
  3. Legitimation: Your consent
  4. Communication of the data: The data will not be communicated to third parties except by legal obligation.
  5. Data storage: Database hosted by Occentus Networks (EU)
  6. Rights: At any time you can limit, recover and delete your information.