It can happen to anyone… your rose bushes are beautiful and blooming like crazy. You spend your days admiring their beauty and then all of the sudden you see it…. the dreaded black spot on roses that can take your entire garden of roses down if not treated.
It happened to me this year. I spent days admiring the fact that my 3 year old rose bush the kids gave me from Mother’s day a few years back was finally happy with its home and was showing off daily.
It was producing so many blooms I could barely keep up with the deadheading once they were spent. that’s when i saw the black spot – at first I tried to say it was the excessive rain we were getting and after a few says I could no longer deny it, it was in fact black spot.
I figured this was a good time to share with you what it is, what is does, and how to treat & prevent black spot on roses.
Roses are generally hardy plants that aren’t difficult to grow. However, they can still be prone to diseases that wreak havoc in your otherwise beautifully blooming rose garden.
Let’s get to the bottom of this plague on our rose bushes.
What is Black Spot?
Black spot is a fungal disease that specifically affects roses. It is caused by diplocarpon rosae, a fungus that develops as black spot on the leaves of roses.
It causes the leaves to turn yellow with black spots (of course) and drop off. Furthermore, it can also seriously weaken rose plants. It is a common disease during hot, humid, or rainy summers and hot days with cool, damp nights.
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When rose plants lose their leaves due to black spot, they are unable to collect and store energy for the winter and to grow well in the spring. This results in weaker growth and reduced blooms.
The fungus can also infect young rose canes. It causes dark purple or black blisters on canes while flowers may show some red spotting.
When plants are infected, they set fewer flower buds and no leaves. These plants also become more susceptible to other problems.
How to Prevent Black Spot
The thing you need to remember about black spot is that it is easier to prevent than to cure. This is because existing spores can remain in the soil and overwinter on leaves and stems. When favorable conditions arise, they can germinate and start destroying your rose garden.
It’s important to give your rose plants ideal growing conditions to make them less susceptible to problems. Plant roses in a sunny location with well-draining soil. Avoid cramming too many in an area to allow for good air circulation. When watering them avoid getting the leaves wet.
Since spores can also be transferred and spread through water droplets, it’s best to spread mulch on rose garden beds. Mulch can prevent water from splashing up from the soil to the leaves.
Black Spot Treatments
If your rose bushes are infected by black spot, there are still measures you can take to save your precious blooms.
First, you can prune infected leaves especially when you do your dormant pruning in early spring. Prune out canes that are showing signs of infection.
Be sure to prune up to 8 inches below the site of infection and make sure to do it in dry weather. Don’t forget to disinfect your pruning shears between cuts using a 10% bleach solution or rubbing alcohol to prevent the spread of spores.
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Be sure to bag up the diseased canes and leaves tightly so as not to infect other areas of your garden. Don’t add these clippings to any compost either as it can spread from there, too.
Second, you can use topical sprays to treat and prevent black spot from invading your roses. Some ideas include:
- Mixing 1 teaspoon baking soda and 1 teaspoon of liquid soap in 1 quart of warm water. This preventive spray can be applied to leaves.
- Insecticidal soaps with added fungicides
- Using 100% cold pressed neem oil as an organic fungicide and pesticide. Avoid applying neem oil within two weeks of using sulfur-based products
- Spreading sulfur powder in your garden beds to control fungal diseases and insect pests.
Preventing black spot is the best approach. But, if you see the spots don’t panic, act quickly and you can save your beautiful rose garden.
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