Flower of red Knockout Rose.  Your Guide to Rose Rosette

Your Guide to Rose Rosette

Many gardeners steer clear of roses in an attempt to avoid the difficulties that may come with growing them. However, in 2000, a rose became available that was low maintenance and disease resistant. Knock Out® Roses soon became a landscapers dream and a customer favorite. But, in recent years, the brand and shrub roses alike have taken a tremendous hit. Despite bouncing back from our recent harsh winter, Knock Out® Roses one nemesis can still take them out — Rose Rosette.

What is Rose Rosette?

Rose Rosette, also known as Witches’-Broom, is a viral disease that is spread by a mite and is fatal to the rose it has infected. The Eriophyid Mite is the carrier of the virus Emaravirus sp. and transmits the disease through a bite. This mite is a quarter of the size of a spider mite and, while it can’t fly, it is so tiny that it floats on the wind from one rose to the next.

The Eriophyid Mite was once considered and used as a natural biological control for wild roses.

In the 1930s, many conservation departments planted these wild roses (Rosa multiflora) for soil erosion control. While these hardy roses seemed to solve the problem, they quickly became invasive.

Rose Rosette appeared in the ’40s and, at the time, was heralded with eradicating some of the wild rose population that the conservation departments could not control.  But, as shrub roses began to appear in our gardens, so too did the virus.

Dark red foliage and thick stems with abundant soft thorns symptoms of rose rosette on shrub rose.
Photo Courtesy of Missouri Botanical Gardens

Does this virus affect only Knock Out® roses?

No. Currently, the virus can affect any shrub rose regardless of variety or brand.

Low-maintenance, drought tolerance, high resistance to powdery mildew, and black spot became the selling point for this highly marketed rose series. As a result, Knock Out® roses became one of the first shrub rose brands to be planted abundantly and en masse.

Although it’s aesthetically pleasing to plant a single variety in large masses and close together, it also allows for the spread of insects and diseases.

How can I tell if my rose infected with rose rosette?

While you may see symptoms on previously infected plants earlier in the season, newly infected roses often show the first signs of disease in mid-July.

Common rose rosette symptoms:

  • Abnormal red coloring in the foliage and shoots
  • Shoots that rise above the rest of the plant
  • An abundance of soft thorns on the stems
  • Thicker stems
  • Deformed and/or yellowed leaves
  • New growth that has a mass of branches on the top — also known as witches broom
Abnormal red leaves grouped together in growth called witches broom on shrub rose.
Photo Courtesy Missouri Botanical Garden

Will rose rosette kill my rose?

Rose Rosette is a fatal virus that affects the rose from the leaves to the root system.  Miticides and horticultural oils are often ineffective, leaving us with the only option to remove and destroy the rose.  

To properly dispose of a diseased rose, follow these guidelines:

  1. Dig the plant out of the ground.
  2. Place it in a plastic bag, taking care to remove all debris.
  3. Dispose of the infected rose.

Can I plant another rose in the same spot I removed my diseased rose?

The answer to this question is highly debated and, depending on who you speak with, could be yes or no.

If you choose to replant with roses, place them singularly through landscape beds instead of en masse. Because this virus only affects shrub roses, planting grasses and other ornamentals between the roses may help to implement a barrier that could possibly reduce and eliminate mite movement.

Choosing to eliminate roses from your garden, though, doesn’t mean you lose out on summer color. Replant with summer-blooming dwarf varieties of hydrangea, butterfly bush, and crape myrtle. Or add color with perennials and re-bloomers like azalea and weigela. With so many summer blooming plants available, roses, while forever a garden staple, don’t have to be your only option anymore.

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