Pests and Diseases: Rose Rosette Disease

 

It is with great sadness that I discuss our topic today: Rose Rosette Disease. You see I fear that the glorious Knockout series of roses may follow the same doomed fate as that of the ubiquitous red tips (Photinia). As I’m sure that you’re aware, red tips have been planted ad nauseum in millions of landscapes around the country; when one particular species is planted in such quantity it is referred to as monoculture. When monoculture occurs, it is very easy for a pest or disease to come in and decimate the overplanted plant. In the case of red tips, a fungal leaf spot known as Entomosporium is the culprit. In the case of my beloved Knockout roses, the causal agent is a virus known as Rose Rosette Disease.

WHAT ARE THE SYMPTOMS OF ROSE ROSETTE DISEASE (RRD)?

If you’re like me, when I check Web M.D. or another medical website, I like to skip right to the symptoms to see if they fit my particular ailment so that’s what we’ll do here. By far and away the most tell-tale sign is a witches broom appearance on the new growth. If you’re not familiar with what a witches broom is, the best way I can describe it is it’s like a really compact, version of the plant itself. Here is a picture that is on the Virginia Cooperative Extension website in case my words didn’t do the description justice. Often times the witches broom is bright red in color on the Knockouts and resembles a bouquet of flowers. Another give away symptom is that of excessive thorniness and extremely flexible new growth…so flexible that you can tie a knot in the stem. If you see either or both of these symptoms, you can rest assured that you have the dreaded Rose Rosette Disease.

 

SO WHAT CAUSES ROSE ROSETTE DISEASE?

There is a tiny, microscopic mite that is 1/100 inch long that is known as the eriophyid mite. It is this rinky dinky little arthropod that threatens to remove the Knockout roses from my gardening palette. Notice I said my garden palette, not the garden palette. These mites transmit the virus that cause RRD…now take a guess how they get from one area to another. They blow along in the wind or hop a ride on an unknowing bird or insect. The frustrated part of me thinks “how am I supposed to fight that? Should I put a bubble around the roses or stick them in a vacuum chamber?” Realistically, all you can do is hope that this miserable little mite doesn’t find his way into your garden.

WHAT CAN YOU DO TO LESSEN THE CHANCES OF RRD AFFECTING YOUR ROSES?

  1.  Buy clean stock. Even if you see a killer deal at the end of the season in your garden center, don’t buy it if you see any of the above mentioned symptoms.
  2. Work cleanly. When pruning your roses, sterilize your pruners often and certainly between shrubs. RRD can also be spread by pruning cuts so make sure that you take care not to inoculate your own shrubs with this lethal disease.
  3. Avoid planting cultivated roses near areas that contain the wild multiflora roses. Your approach could be to remove the wild roses as they serve as inoculum for the disease. Or if you know that wild multiflora are in the area, you could avoid planting the Knockouts at all (that thought makes me sad).
  4. If you observe RRD on your plants, you must remove and bag the infected roses. Don’t try to compost them or let them ride in the back of your truck on the way to the landfill…you’ll just be spreading your misery to other gardeners who live along the path to the landfill.
  5. There’s always chemical control but that’s not a philosophy that I really buy into. My theory with plants is that they will either live or die trying. To me, it’s easier to just remove the roses and count your losses.

 

I should note that RRD affects other types of roses but I’m most concerned about the Knockout roses. They are an absolutely delightful plant to cultivate and they reward you many times over what you invest in them. I am as guilty as the 1990′s landscaper who installed red tips at every job. I use them in almost every landscape I design and I realize that I need to curb my enthusiasm so that I don’t add to the monoculture of Knockouts. But it’s a really hard plant to replace…what other shrub blooms from April to December, doesn’t require spraying, and is as beautiful as a rose? If you have any ideas, please e-mail me at stacey@midatlanticgardening.com or leave me a comment below. Happy rose gardening!

December 6, 2011Permalink 13 Comments

13 thoughts on “Pests and Diseases: Rose Rosette Disease

  1. Pingback: Plant Profile: Adagio Maiden Grass (Miscanthus sinensis 'Adagio'Mid-Atlantic Gardening

  2. STACEY:

    Reading your article on Rose Rosette Disease, We live in Spartanburg SC and have about 100 rose bushes (well at the peak) than last year we noticed this “weird” growth, this year our roses are horrible, dieing back, strange growth, every symptom of RRD. Every rose is infected and will have to be removed, my wife is sick over this,not to mention all the time and money. looks like marigolds will be going in.

    Mike D

    • Mike, I’m so sorry to hear that! That must be heartbreaking. I think that the Knockouts are starting down the same path as redtips. In my opinion, it’s still worth planting a few because you just can’t beat them for color. Best of luck as you work on your rose-less garden. :(

  3. Stacy,
    I live in Charlottesville VA and your article sadly helped me identify the problem of RRD on 3 double red knockout roses that were glorious along my garage where I’d walk multiple times a day. Took prunings to a nursery today and horticulturalist confirmed the diagnosis. Only point I differ with you is 3 plants don’t make a monoculture. It’s very common in installations to plant in repeating groups of 3 or 5. Like you, many of us loved their low maintenance high color value in the summer. Comparable alternatives are hard to find. Many thanks for your article.
    Georgia

  4. Hi Georgia! I’m very sorry to hear of your roses…it truly is depressing. I didn’t mean to insinuate that your 3 roses were a monoculture. I meant that when they are planted at your house, your neighbor’s, the shopping center down the street, the median entrance to your subdivision, etc. that makes them much more vulnerable to being decimated by a pest or disease. Take comfort in knowing that you are not alone…we are removing more and more of them from our landscape each year. Take care!

  5. “If it’s too good to be true, beware!” Guess that will apply to KnockOut Roses from now on. I have 6 planted and so far, neither mine nor my across-the-street neighbors appear to be infected. However, we are one village within a very large neighborhood, and the KnockOut Roses are abundant throughout this area…all up and down the Parkway running through the neighborhood. I will keep a watch on mine, and hope for the best. They have been so easy and just gorgeous from April through December, and even some blooms into January this year! Sob!

  6. Years ago I had to destroy my beloved Grootendorst as it had rose rosette. I had to hack it down with my own hands.
    I have always had several of the wild rose cultivars in my yard and all was fine till this year
    Now one of them has died horribly of rose rosette and…..my sage plant looks like it has caught it as well
    Is this possible?

    • I don’t believe that sage can have RRD. Generally, viruses are very specific as to the host that they infect. I am sorry that you have lost your roses…it is very depressing as a gardener :(

  7. My knockout roses started the down fall of all my roses. I have the dreaded Rose Rosette disease in my rose garden. Have lost half my roses and soon I will not have one single rose on the farm. So sad. Is anyone working on a cure? The old fashioned roses have been here for at least 50 years. I am so sorry that I planted the Knock Out roses.

    • That’s terrible Christine! I am so sorry to hear that you have lost so many. Everywhere I look, the Knockouts are croaking. It seems to be particularly bad where “mow, blow and go” lawn companies are taking care of the plants. They just shear them back and keep moving which spreads the disease like wildfire. Since it’s a virus (or virus-like) I don’t know that they’ll ever find a cure…the common cold still rages every season. It’s a definite testament to avoiding monocultures, although I am as guilty as the rest for planting tons of them.

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