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Avoid The Top 5 Diseases For Double Knockout Roses

So, you’ve fallen in love with Double Knockout roses! But what if they are susceptible to diseases?

unnamedSo, you’ve fallen in love with Double Knockout roses!  And what’s not to love?  So many benefits and bigger, better blooms than traditional roses!

But chances are that whether you are considering the purchase of a Knockout rose or have already added one to your landscape, you’re curious about the diseases that plague the traditional rose varieties you’ve always known.

Can Knockouts be affected by the same plights?

Double Knockout rose bushes are extremely disease resistant. They’re much more resistant than traditional rose varieties.

Unfortunately, when you’re dealing with nature, beauty doesn’t equal perfection.  Under poor conditions, double knockout roses can still get hit by some diseases.

Let’s take a moment to learn about the five most common diseases that a Knockout rose can face, and how to prevent them all together!

The five most common diseases that could affect a Knockout rose are:

  • Rust
  • Black Spot
  • Botrytis Blight (Gray Mold)
  • Powdery Mildew
  • Stem Canker



Double-Knockout-RoseNamed for its orange, powdery appearance, rust is a disease common to roses that appears first under the leaves and soon spreads to the rest of the plant.  Rust is a fungal disease that spreads in moist air.

Black Spot

The appearance of circular black spots on the leaves or stem of a rose is known as the fungal disease Black Spot.  This particular rose ailment can quickly destroy an affected plant if left untreated.

Botrytis Blight

Sometimes also called Gray Mold, Botrytis Blight is a fungal disease that prohibits new buds from opening and seals them in a grayish mold.  Open rose blooms become covered with brown and/or yellow markings and petals become brown and droopy.  It spreads in cooler temperatures and moist air.

Powdery Mildew

Powdery mildew is a fungal disease affecting roses that causes a white, powdery substance to appear along the top and bottom of both foliage and stem, and occasionally even the on blooms themselves.  This disease prevents your Knockout from reaching its maximum height, and causes the affected leaves to become dry and eventually fall off.

Stem Canker

Pink-Double-KnockoutStem Canker is a disease caused by fungus that thrives in water and then gets into the canes of your rose through cuts in the stem’s skin.  Reddish brown in color, these cankers are small spots that crack and swell, eventually causing the stem — and all the foliage and blooms above it — to die.

Disease Prevention

Those don’t sound like much fun to deal with, right?  Then let’s get to the good news!  As you may already know, Knockout roses are hardier than other varieties.  So while these five diseases can happen, your Knockout is far less susceptible to them than other varieties may be.

You can ensure that your rose does not succumb to disease with the minimal effort of just a bit of preventative maintenance.

First of all, avoid watering in the evening when possible.  If you must water your roses in the evening, such as if temperatures or drought require it, take care to do so only at soil level.

89622591.y3BT17rA.FrankfortKnockoutscopy_01You should never purposely wet the foliage or blooms of your Knockout.  Moistening more than the soil is the easiest way to promote disease; avoiding it is the easiest way to prevent disease!

If at some point your Knockout does become affected by any of these ailments, you can prevent them from spreading and causing any further harm by simply trimming off any effected parts and disposing of them properly, and cleaning up fallen leaves and blooms regularly.

Don’t forget to clean your gardening tools well if used to prune a diseased rose.
Chemical solutions, such as fungicide, should be used only as a last resort.

Remember, when it comes to Knockout roses, prevention is better (and easier!) than any cure.

As a gardener and plant enthusiast I’ve loved growing trees and shrubs my entire life. Unknown to most, there are always new faster fruiting and double blooming plant hybrids emerging on the scene. I often feel the need to share my plant knowledge and new trends with the growing gardening community through my blog!