Black Spot On Rose Bushes (BSR)
The term “black spot” refers to a dark area or discoloration on the rose petals. There are many theories about why some roses have such areas while others don’t.
Some believe it’s due to genetics, but there is no conclusive proof yet. Others think that the black spots could be caused by bacteria or viruses, which then cause other problems like infection, wilting and death of the plant. Still others believe that the black spots are caused by chemicals used in commercial fertilizers and pesticides.
There are several methods to remove these spots from your roses. You can use bleach or ammonia, both of which will kill off any bacteria or virus present on the rose.
But they won’t solve the problem completely. If you want to get rid of all traces of black spot on your roses, you need something else: natural remedies!
Natural Remedies For Black Spot On Roses
1. Hydrogen Peroxide For Black Spot On Roses (H2O2)
Hydrogen peroxide is one of the most effective ways to get rid of black spot on roses. It kills off all bacteria and viruses present on the rose, leaving behind only its own dead tissue.
At this point the black spots will disappear on their own.
How to apply: Get a spray bottle and put 3 percent food grade hydrogen peroxide in it. Next, water it down so that the concentration is about 30 percent.
Spray your roses with this mixture at least once every three days. Do this for about two weeks and the rose’s discoloration should start disappearing.
Note: You can also use 20 volume or 30 volume hydrogen peroxide instead of food grade. However, the food grade option is recommended since it doesn’t have any additional ingredients that could cause harm to your rose.
2. Baking Soda For Black Spot On Roses (NaHCO3)
Baking soda is a safe yet effective way to get rid of black spot on roses. The key is to using the right concentration.
How to apply: Dissolve one teaspoon of baking soda in one litre of water. Once the solution is ready, apply it directly on the affected parts.
Do this at least once every three days.
This process should be continued until all signs of black spots have disappeared from the rose. Once the symptoms are gone, continue spraying weekly to prevent their return.
3. Neem Oil For Black Spot On Roses (Azadirachta Indica)
Neem oil is derived from the neem tree, which is native to parts of India and Asia. It has several beneficial properties for both humans and plants, a few of which are described below.
Neem oil is a fungicidal agent. This means that it can get rid of fungal infections on the rose without causing any harm to the plant.
It is a non-toxic option, meaning that it can be used safely and won’t cause any harm to the rose.
How to apply: Get a spray bottle and put a few drops of neem oil in it. Before you apply the mixture, dilute it with water so that the neem oil concentration is 1 to 5.
Next, add this mixture directly on the rose and also on all affected parts. Do this once every three days for about two weeks.
You can also use pure neem oil instead of the diluted spray. Rub a little bit of it on the affected parts of the rose and make sure that all parts are covered.
Do this once or twice every day for a week and then once every two days until the rose is cured. Keep doing this to prevent future outbreaks.
Frequently Asked Questions
What Are The Black Spots On My Rose?
The black spots on your rose are a common sign of fungal infection. The most likely cause of this is the fungus gnats, which can be found feeding on the underside of some leaves.
These gnats spread black spot via their feces, so if you have a serious infestation it’s important to take steps to eliminate them.
What Is Black Spot On Roses?
Black spot is a common fungal infection that affects roses. It’s easy to identify due to its name and its appearance; black spots on the leaves that look a bit like mud.
This fungus is carried by fungus gnats, so make sure you get rid of these before they can spread the infection further.
How Do I Get Rid Of Fungus Gnats?
Fungus gnats are one of the most difficult types of pest to get rid of. They thrive in wet soil and spread quickly.
If you have a severe infestation, you should probably think about throwing away the plant and getting a new one. It’s better to be safe than sorry!
If you want to keep your rose, however, there are a few steps you can take.
Empty all the soil out of the pot and let it dry in the sun for at least a day. You can leave it out until you’re sure that all the fungus gnats are dead.
Add some diatomaceous earth to the soil. This is a natural way to kill off any pests that could be living in the soil.
Sources & references used in this article:
Genetic analysis of resistance to blackspot (Diplocarpon rosae) in tetraploid roses by B Von Malek, T Debener – Theoretical and Applied Genetics, 1998 – Springer
Components of partial resistance to black spot disease (Diplocarpon rosae Wolf) in garden roses by AG Xue, CG Davidson – HortScience, 1998 – journals.ashs.org
The toxicity of sulphur dioxide to Diplocarpon rosae Wolf causing blackspot of roses by PJW Saunders – Annals of Applied Biology, 1966 – Wiley Online Library
Applications of Potassium Silicate Decrease Black Spot Infection in Rosa hybridaMeipelta'(Fuschia Meidiland™) by JH Gillman, DC Zlesak, JA Smith – HortScience, 2003 – journals.ashs.org
Identification of molecular markers linked to Rdr1, a gene conferring resistance to blackspot in roses by B Von Malek, WE Weber, T Debener – Theoretical and applied genetics, 2000 – Springer
Two genetic linkage maps of tetraploid roses by S Rajapakse, DH Byrne, L Zhang, N Anderson… – Theoretical and Applied …, 2001 – Springer
Disease resistance breeding in rose: current status and potential of biotechnological tools by T Debener, DH Byrne – Plant Science, 2014 – Elsevier
Construction of a BAC library of Rosa rugosa Thunb. and assembly of a contig spanning Rdr1, a gene that confers resistance to blackspot by H Kaufmann, L Mattiesch, H Lörz, T Debener – Molecular Genetics and …, 2003 – Springer