Black Spot on Roses: Prevention and Treatment
This little landscaping rose, planted in partial shade, has a bad case of black spot.
The Dirt Farmer
Black Spot: Appearance and Causes
Caused by the fungal pathogen known as Diplocarpon rosae, black spot is the leading fungal disease on roses in the world.
What does black spot look like?
Black spot first appears as feathery-edged black spots on the leaves (usually the lower leaves) of rose bushes. Sometimes, the damage looks like a cigarette burn.
As the black spots grow larger, the leaves turn yellow and drop off. On stems, black spot appears as irregularly shaped blotches. These blotches, which may be deep purple, black, or dark brown, eventually blister.
If black spot is left unchecked, it can work its way up the stems of rose bushes, defoliating the bush as it goes and ultimately killing it.
What conditions promote black spot?
Warmth, humidity and overnight wetness on rose leaves encourage Diplocarpon rosae to germinate and grow.
Insects, people, pets, water, infected plant parts, dirty gardening implements—many things can spread the disease throughout the garden.
See "spot" run! Healthy roses begin with simple, basic gardening practices. This landscaping rose, previously infected with black spot, is a great example of that.
The Dirt Farmer
1. Choose the Right Location
Healthy plants are better able to resist disease than unhealthy ones. To promote the health of your rose bushes, make sure that they are planted in the right spot.
Proper Planting
In order to thrive, roses need plenty of sunlight and lots of room for good airflow.
If your rose bushes are in a shady, crowded bed, draped with vines and/or surrounded by weeds, chances are they will develop black spot or some other fungal disease.
After being moved to a sunnier, less crowded location and severely pruned to increase airflow and remove infected plant parts, the landscaping rose featured at the top of this page is healthy and black spot-free once again.
The Dirt Farmer
2. Increase Airflow: Prudent Pruning
In addition to adequately spacing plants, pruning your rose bushes will ensure good airflow.
- Using a by-pass pruner, snip out diseased and dead canes, leaves and flowers, as well as crossed or rubbing canes, particularly those in the center of the bush.
3. Keep Your Garden Neat and Clean: Healthy Hygiene
Keep the area around your rose bushes free of weeds and debris (such as rose bush clippings).
Weeds not only increase the humidity that encourages black spot, but they also provide food and shelter for pests.
Rose bush waste may harbor Diplocarpon rosae, the fungus that causes black spot. After pruning, be sure to remove all buds, leaves, stems, and branches from around the bush. Diplocarpon rosae spores can overwinter on discarded leaves and stems and, when conditions are right, germinate, reinfecting your rose bushes.
Also, because roses are prone to disease, avoid composting rose clippings. Doing so could spread black spot (as well as other diseases, such as mildew) throughout your garden.
After pruning infected rose bushes, clean your pruning sheers by wiping them down with rubbing alcohol to prevent the spread of black spot. Diplocarpon rosae fungus can live on garden tools (and in soil) for up to a month!
The Dirt Farmer
4. Keep Humidity Down: Wise Watering
Water rose bushes at their bases, not overhead, either by hand, through direct-drip irrigation or with a soaker hose.
Keeping leaves dry during watering will make them less susceptible to black spot and other fungal diseases (like powdery mildew) that require moisture in order to germinate.
Knock-out roses are among the many black spot-resistant rose bushes available today.
The Dirt Farmer
5. Smart Selection
One of the easiest ways to avoid black spot in the rose garden? Opt for rose bushes that are less likely to succumb to it. Although no rose bush is impervious to the disease, some are more resistant than others.
Some Black Spot-Resistant Varieties of Roses
| MINIATURES | GRANDIFLORAS and FLORIBUNDAS | HYBRID TEAS | RUGOSAS | CLIMBERS | SHRUB ROSES |
|---|---|---|---|---|---|
Always a Lady | Angel Face | Charlotte Armstrong | The Fairy | Eden | Baby Love |
Black Jade | Fashion | Chrysler Imperial | Blanc double de Coubert | New Dawn | Carefree Series of Roses |
Green Ice | Love | Granada | Rugosa Alba | Pinkie | Knock Out Roses |
Minnie Pearl | Red Gold | Mr. Lincoln | Rugosa Magnifica | Red Climber | Sea Foam |
Watercolor | Sonia | Pink Peace | Rugosa Rubra | Royal Sunset | Winter Sunset |
This miniature rose bush has had a mild case of black spot, mostly due to wet, hot weather. I gave it a good pruning to increase the airflow and remove infected foliage.
Jill Spencer
6. Timely Treatment
Although I do not use any in our garden, treating your rose bushes with fungicide will also lessen the likelihood of black spot. Those who intend to show their roses (and are unwilling to tolerate any black spot damage) are most likely to apply traditional or alternative fungicide treatments.
Begin fungicide treatments in early spring, when the first leaves emerge, and continue spraying into fall. Follow the directions on the label of the fungicide to the letter.
Many treatments for black spot must be applied every 7 to 14 days, and they can be costly over time.
If your roses are simply for the enjoyment of yourself, your family and your friends, I recommend skipping them and relying on good gardening practices instead.
Miniature roses are just as prone to black spot as other types of rose bushes.
Jill Spencer
Some Traditional Fungicides and Their Product Names
- Captan (Captan)
- Chlorothalonil (Ortho Garden Disease Control, Bonide Fungonil Multi-purpose Fungicide, Daconil, Bravo, Echo, Fungonil)
- Mancozeb (Mancozeb, Stature, Dithane M45)
- Myclobutanil (Spectracide Immunox Multipurpose Fungicide, Eagle)
- Propiconazole ( Banner Maxx, Bonide Infuse, Fertilome Systemic Fungicide)
- Thiophanate-methyl (Fertilome Halt Systemic, Fungicide Fungo Flo, Quali-Pro TM, Systec, Cleary’s 3336)
Some Alternative Fungicides and Their Product Names
(These can be just as harsh as the others. Again, follow the directions for use carefully.)
- Potassium bicarbonate (Bonide Remedy Fungicide, Armicarb 100 )
- Copper hydroxide (Hi-Yield Copper Fungicide, Kocide, Tenn-Cop, Basicop)
- Copper salts (Bonide Liquid Copper Fungicide)
- Lime sulfur (Lime Sulfur)
- Neem oil ( 70% Neem Oil)
- Sulfur (Sulfur Dust, Wettable Sulfur)
This miniature rose bush is a grafting of red, cream and pink roses. The red rarely blooms at the same time as the rest.
Jill Spencer
The Dirt Farmer
Resources
"Blackspot." Rose Magazine. Rose Magazine Inc, 2012. Web. 5 July 2012.
The Maryland Master Gardener Handbook. University of Maryland Extension Master Gardener Program. 2008. Print.
"Save Your Roses From Black Spot." Better Homes & Gardens. Meredith Corporation, 2012. Web. 5 July 2012.
Wallis, Chris, et. al. "Black Spot of Roses." Fact Sheet: Agriculture and Natural Resources. Ohio State University, 2008. Web. 5 July 2012.
Watt, Bruce A. "Black Spot of Rose." Cooperative Extension: Insect Pests & Plant Diseases. The University of Maine, 2010. Web. 5 July 2012.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2012 Jill Spencer
Comments
Jill Spencer (author) from United States on July 06, 2012:
Hi pagesvoice! Glad to meet another rose grower. I'm relatively new to it, too, having only started about 7 years ago. Right now, just deadhead your roses and remove damaged and/or diseased bits. In the fall, you'll need to cut them back and mulch. Bet those blooms are going to be beautiful! Have fun, The Dirt Farmer
Dennis L. Page from New York/Pennsylvania border on July 06, 2012:
Voted up, useful and interesting. You have given the reader a useful Hub, filled with nuggets of great information. Interestingly, although an avid gardener of perennials and vegetables, this is my first year planting rose bushes. I mulched them well when I planted, but I still have questions about when and how often to prune? I am just starting to get rose buds and like a kid in a candy store, I am eagerly awaiting their blooms.
Jill Spencer (author) from United States on July 05, 2012:
@ terrektwo --Thanks for the vote! Just started another hub today on composting. Hopefully I'll finish it very soon. Take care!
Candle Hour from North America on July 05, 2012:
great hub with some excellent tips. thanks for sharing and voted up as well, will be watching for more :)
Jill Spencer (author) from United States on July 05, 2012:
Hey Jackie Lynnley! I hadn't thought of that: black spot is so common that it does seem normal on roses. Hope you get your roses in tip-top shape now. Thanks for the vote. Glad you stopped by. --The Dirt Farmer
Jackie Lynnley from the beautiful south on July 05, 2012:
Glad I found you too. I love roses but hate how they get and I thought it was normal, now I see it is not. Love your white one! Love your hub, thank you and voting up!
Jill Spencer (author) from United States on July 05, 2012:
Hope that takes care of your problem, TravelAbout. Thanks for stopping by and commenting. (:
Katheryn from United States on July 05, 2012:
Dirt Farmer
I have been getting black spots on many of my garden plants. I glad I saw this hub as it sounds exactly like the problem I am having. I also water all of the plants rather than just around the base. I will get some fungicide and try. Thanks for sharing. Voted up.
