Battling Black Spot

                     Unwelcome Rose Disease


Spring has sprung and you’re looking forward to
another season of Rose Blossom glory. Before the
first leaves unfurl, however, you may need to take
some preventive action against the dastardly
Black Spot Fungus Disease.
While some black spot can be tolerated by your
roses – it should not be left unchecked – or it could
defoliate, weaken and even defeat your Rose shrub.
Some simple precautions and organic solutions
to this unwelcome rose bush disease follow.



    I Treat My Roses with
    Why Do They Have Black Spot Fungus?

You’ve been doing all the ‘right’ things for your roses — watering from below, planted them with proper spacing, pruned them correctly to provide air and light, mulched to prevent splash up, fed them as needed, provided good organic amendments, cleaned up debris and watched for pests.  And for good measure…you’ve even sung to them…  :=)  Well… just checking to see if you’re following along diligently… :)  But hey!  Singing is good too!  I do it…I confess.. not just in the rose garden, though  …  :  -)


Yet.. despite all your good intentions and diligent work,  you’ve spotted  dastardly dang spots all over your rose leaves — BLACK SPOT – that UNwelcome rose fungus!   (But then what rose disease IS welcome… ?)   What could you be doing wrong?!

Black Spot rose disease can quickly deform and destroy the foliage of your beloved roses..Sometimes , no matter how diligent we try to be, daily rainfall, heavy dew or lasting humidity just make things all too ideal for black spot spores and powdery mildew.  Or perhaps you missed a protective preventive “medicinal’ application during the season, which allowed the infection to take hold. If you live in a normally humid or rainy climate, then preventive ‘medicine’ should be a routine maintenance task if you grow roses.  Some roses are more black spot and mildew resistant, and you should check locally to see what grows the best in your area.  New varieties of robust roses are being developed yearly.


Whatever the reason that black spot has reared its ugly facade on your leaves , you want it gone…and you’re not going to put up with this uninvited harassment for your roses!  You’re thinking of resorting to some ‘heavy ammunition’ ‘to hunt it down in its tracks!


    Organic Black Spot Treatments – ‘Green’, Earth Friendly
    Weapons Against Rose Disease

Well– whooaaa there just a bit!…  The best practice for your roses –and for the rest of us  and generations to come — is to use the least toxic means of treatment first.


Some rose disease treatments are the most toxic sold legally.Please note that some of the most toxic chemicals permitted legally  are used for roses! Serious consequences to the environment as well as to our own health and all wildlife and companion animals are possible. Weighing the necessity of using chemicals is always advised — no matter what we are trying to ‘battle’  –be they for our roses — or insect pests that can drive us personally wacky. Many rose gardeners grow roses successfully with more ‘benign’ means of combat when needed – along with some black spot tolerance.



Prevention is always the best medicine, but as noted, it isn’t always possible to completely avoid infestation.  However, to aid prevention for your more susceptible rose plants,  begin in early spring to apply organic black spot treatments such as  sulfur or fungicidal soap.  Apply while the plants are ‘napping’ – or dormant – prior to the buds opening up to form leaves (bud break).  These applications will only work , however,  if they cover the plant and leaves before the spores find them. Thus..this is a preventative.


Spores will ‘awaken’ and want to germinate in temperatures around 75 degrees F.  Black spot, along with powdery mildew and rust afflictions will tend to keep their distance for a while with these applications, since the spores cannot germinate in the sulfur or fungicidal coating. If it rains, however, these applications will wash off,  so you will need to continue to apply.  But if  your climate is ripe for these uninvited visitors, your persistence will help give your roses a running chance to get a good spring start and gain strength without the hassle of these intruders weakening their well-being.


Sulfur spray is deemed an organic treatment in gardening circles, in that it occurs naturally in nature as a basic element and has been used by generations of farmers safely. Cornell University has produced a simple, organic formula that can help stave off the dastardly black spot,  using ingredients that most of us keep around the house. The formula is mixed and used to coat the leaves, top and bottom.

Here’s the formula:

Mix together into 1 gallon of water and Spray on liberally:

  •  1 tsp. of canola oil
  • 3 tsp.of baking soda

Or Try

  •  1 tsp. baking soda in 1 Qt. of water
  • add a few drops of liquid dish soap to help it stick


This formula can also be used for powdery mildew, which appears in similar conditions.

You’ve covered the early pre-leaf emergence period.  Now…after the leaves are OPEN…apply a fungicide.


Continue with the sulfur and/or fungicidal soap sprays, or try Neem products,which are less toxic than conventional sprays and will  also attack mite and rose pests as well!  Only new infestations can be prevented with this application, so you’ll need to keep at the spray regimen through the summer, especially if the weather stays wet or humid.


    If All Else Has Failed – Black Spot  Disease is


If the condition is so severe early on that you fear losing the rose plant, then you may decide  to resort to a a less earth-friendly ‘big gun’  fungicide to try to save your rose plants from massive to total defoliation.  However, be aware that fungus can become resistant to fungicides, so rotating different ones is advised. Check with your local garden center for available chemicals to apply.  Settle on three that you can use in succession if needed, using a different one each time you apply.


As early summer dawns and your Neem applications have done the trick to prevent infection and drier weather prevails, your summer can be a breeze of simply pure enjoyment of the gorgeous blooms, avoiding chemical applications altogether!


    Enjoy the Rose Show – and Allow your Permissive Side


As the summer progresses, you can sit back and enjoy the show as many repeat bloomer rose shrubs, such as Old Garden/Antique/Heritage varieties and Knockout Roses, which tend to be quite resistant to the black spot fungus, continue to reward you with random displays of their flowery finery.  Along with your relaxed enjoyment, you may want to allow your tolerance meter to work and develop some ‘blind spots’ in your rose-colored ‘perfection’ view-master…. That is not to say you should ignore black spot or other maladies…but just look past some of the blemishes they may have wrought to see all the glorious beauty that still abounds.  If your roses have come this far now with most of their leaves, they are likely out of the biggest danger.


Once your rose shrubs have made it into the waning days of the growing season, some black spot on the rose bush is not likely to cause death or leave your roses with permanent damage, so you may wish to relax a bit and just tolerate some spots on your shrubs. Continue to remove any leaves from the ground and the bush as you can to keep as many spores in check as convenient, and definitely do a total fall clean up of all diseased debris.


Replace the mulch with fresh, new covering in the spring.  An inch or so of good, quality compost  is favored over wood, rubber or bark-type mulches. It’s better to prune away any diseased damage to the canes in the spring if you haven’t managed to get to them before fall.


Proper nutrients and hydration will help keep your rose plants strong. A previous study showed that fewer fungicides applications in regular high-humidity areas were required and less defoliation resulted in systemically healthy roses treated to proper nutrients! *   Healthy specimens of any species  are, of course, more resistant to disease.


Along with proper sanitation and clean up of all diseased material and the pruning and disposal of infested canes, if you have cared for them properly with healthy watering and feeding routines this year, your roses should emerge next spring with vigor to delight you for the new season.


    Be A Step Ahead of Black Spot Disease
    and Combat Ready Next Spring


Start your preventive regimen next spring before the leaves sprout to fight any spores left behind, looking for the right conditions to emerge.  Be combat ready…and make your strike of protection first, before the weather warms to awaken the enemy!



             ‘Management Key to Controlling
                      Blackspot Disease in Roses’ -

     Highlights of Agricultural Research
  Volume 43 Number
  Summer 1996
Alabama Agricultural
     Experiment Station 




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