There is nothing more heartbreaking than seeing those dreaded black spots on the leaves of our rose plants.
Fear not, the black spot might be a scary disease but it is not a death sentence to your roses.
Read on for this complete care guide to rose black spots as well as remedies that you can make at home to treat your roses.
What Are Black Spots On Roses?
Black spots on rose leaves (or simply, black spots) are a type of fungal-based disease that affects roses.
As their name implies, the fungus causes the leaves to develop dark spots on its leaves, causing the plant itself to weaken.
Black spot is a very serious disease for roses, as it has a high likelihood of wiping out the plant when left untreated.
Rose Black Spot Symptoms
Rose black spot lends its name from the irregular-shaped patches of black that cover the top surface of the roses’ leaves.
As the disease starts to progress, the black spots get larger and begin to spread.
In the later stages of the black spot, the remaining leaves turn yellow and drop from the plant.
After the first set of leaves dies off, the rose plant tries to regrow new leaves late in the season.
At this stage, the new growth is not strong enough to survive the oncoming winter.
When winter comes, the ill rose plant is unable to sustain itself and dies during the dormant winter season.
What Causes Black Spots On Rose Leaves
A black spot is the result of a fungal infection.
It is caused by the fungus Diplocarpon rosae, which causes the plant foliage to slowly die, resulting in the signature splotches of black.
Black spots thrive in wet, cool conditions.
How To Prevent Black Spots On Rose Leaves
Like many other rose diseases, black spot preys on vulnerable plants.
One of the keys to preventing black spots on roses is to raise healthy plants.
Here are some tips:
Minimizing Excess Moisture
As we’ve discussed briefly, the black spot is exacerbated by moist, cool weather conditions.
As a result, it is crucial to reduce any opportunity for unnecessary moisture.
This is especially useful for gardeners who live in consistently humid climates.
Avoid overhead watering as this causes the leaves to become wet, which harbors fungus that can potentially spread disease.
Instead, it is advised to water your roses close to the base of the plant.
Additionally, it is often recommended to water your plants early in the day, so that there is enough time for the sun to evaporate any residual moisture during the daytime.
Providing Full Sun
Planting your roses in a location that receives full sunlight is a crucial step in the prevention of black spots.
Unless otherwise specified, it is necessary to provide at least 6 hours of sunlight for your rose plants.
This is beneficial to their health, but it is also helpful in evaporating excess moisture that has the potential to harbor fungus.
Increasing Air Circulation
Maximizing the airflow ties into minimizing excess moisture.
An increase in air circulation helps promote evaporation and prevents trapped moisture from harboring fungal spores.
Regularly prune your rose bushes when necessary.
Oftentimes, rose bushes will need to be pruned as they are exiting their dormancy. This is done in the late winter to early spring.
Remove any damaged foliage followed by crossing canes.
After pruning your rose plant, collect any fallen leaves and branches and dispose of them properly.
This prevents the plant trimmings from potentially harboring fungus and spreading to the rose plant.
In addition, spacing out your rose plants during initial planting will help prevent overcrowding, which inhibits airflow.
Depending on the mature size of your rose variety, you will want to space your plant between 2 to 4 feet apart from one another.
How To Treat Black Spots On A Rose
Treating black spots on rose leaves can be tricky, but it is by no means impossible.
Keep in mind that black spots can not be reversed.
Once a leaf is infected with a black spot, there is no healing.
However, you can use homemade remedies or fungicides in order to stop the black spot in its tracks.
8 Homemade Remedies For Black Spots
Sometimes the best remedies for disease can come from everyday household items that you have around the house, be it your kitchen or your bathroom, or your garage.
Here are some examples of remedies you can make at home that can be used to stop the spread of black spots.
Of course, these homemade remedies are not miracle one-time cures.
You will need to apply these remedies in several rounds in order for maximum effectiveness.
1. Baking Soda Spray
Combine the following:
- 1 teaspoon of baking soda
- 1 teaspoon of liquid dish soap
- 1 quart of warm water
Spray the leaves of the plant thoroughly. This mix works best as a preventative, rather than a treatment for existing black spots.
2. Vinegar Spray
Combine the following:
- 1 tablespoon of white distilled vinegar, diluted with 1 cup of water
- 1 1/2 tablespoons of baking soda
- 1 tablespoon of dish soap
- 1 tablespoon of vegetable oil
- 1 gallon of water
Place this in a spray container and apply this to your rose plants. This can be used as a preventative, especially after a rainstorm when the foliage is freshly wet.
3. Hydrogen Peroxide
Combine the following:
- 1 tablespoon of hydrogen peroxide (3% concentration)
- 1 cup of water
Spray this on your rose plants in order to slow down the spread of black spots on your rose leaves.
4. Milk
Combine the following:
- 1 part milk
- 2 parts water
While this will work for emergencies, this particular home remedy does not kill the spores.
However, it does slow down the spread long enough to effectively control the black spots.
In addition, any solution that contains milk has a limited shelf life and loses its potency quickly.
5. Neem Oil Spray
Neem oil is a horticultural oil that is derived from the seeds and fruit of the neem tree.
It is beloved by many gardeners because it is completely organic and is used as not only a fungicide but an insecticide as well.
You can either opt to purchase pure neem oil or a manufactured spray that contains neem oil.
However, pure neem oil must be diluted with water.
Dilute 2 tablespoons of neem oil with 1 gallon of water. Spray this mixture on your affected plants.
Avoid spraying neem oil on hot, sunny days. The heat can cause the neem oil to burn your plant.
Lastly, it is extremely important that you do not apply neem oil within two weeks of using sulfur to treat your plant.
6. Sulfur
In gardening, sulfur is usually added to the soil to lower the pH level, but it can actually be used as a very effective fungicide.
Sulfur has often been found to be the preferred fungicide when it comes to treating black spots on roses.
Sulfur can be used as a dry mixture that is powdered onto your plants, or as a liquid spray solution.
When handling sulfur, exercise extreme caution as this can be mildly toxic to humans and animals.
We advise anyone handling sulfur to wear protective equipment such as gloves, masks, and eye coverings.
In addition, sulfur corrodes metal, so plastic is the preferred material to use when mixing your solution.
Avoid using sulfur on your plants in hot & sunny weather, as this might cause the foliage to burn.
7. Dust Mixture
Combine the following:
- 9 parts powdered sulfur
- 1 part dry arsenate of lead
Apply the dust mixture on a warm, dry day with little wind.
8. Liquid Mixture
Combine the following:
- 4 tablespoons of sulfur powder (check the label to see if it is able to be mixed with water)
- 1 gallon of water
Combine this into a plastic spray bottle and apply it to afflicted areas of the rose plant.
Best Fungicide For Black Spots On Rose
There is a multitude of fungicides on the market that specifically treat black spots on rose plants, however, the best fungicide that we recommend would be one that is sulfur-based.
In our previous section, we touched on how to effectively use sulfur to your advantage when it comes to stopping black spots.
FAQs
Can rose black spots spread to other plants?
Yes, while black spot is commonly associated with roses, it has the potential to spread to other ornamental plants.
Should I remove the roses with black spots?
Yes. As we’ve discussed previously, the black spot cannot be reversed but can be stopped in its tracks.
The first step to preventing the spread of black spots is eradicating any affected parts, including the roses that already have black spots.
Should I cut off black spot leaves on roses?
Yes. Just like the roses with black spots, the black spot leaves should be cut off as well and disposed of completely.
Using a sharp pair of pruning shears, cut off any signs of disease or damage that you can see on your rose plants.
After fully pruning your infected plant, wrap the diseased foliage in a strong plastic bag and dispose of it.
Immediately clean your pruning shears by wiping them down with rubbing alcohol in order to clean them of any residual fungus.
Conclusion
As gardeners, there’s nothing we wouldn’t do to give our plants healthy, fruitful lives.
It can make your heart sink when you realize your rose plant has a black spot.
Luckily, with simple and easy solutions, we can swiftly eliminate black spots altogether.
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