By now, most people who garden, and many who do not, have heard about Rose Rosette Disease (RRD), the virus affecting roses around Dallas and throughout the central, southern and eastern United States. What you may not have heard is the extent to which this disease could eradicate every known variety of rose in this country from the center of the US to the east coast if we do not stop planting them immediately.
Rose Rosette Disease is a virus carried by the microscopic eriophyid mite (Phyllocoptes fructiphilus), a wingless parasite. This tiny arachnid has no method of self-ambulation and is propelled by the wind. This is very important in understanding the danger of this disease. As the mites are distributed on prevailing breezes, they land on a rose, suck on the leaves of the rose and transfer the virus into the vascular system of the plant. The mite lays eggs on the rose which hatch producing more infected mites which then move forward on the next breeze to the neighbors’ roses. Once a plant is infected, the virus additionally spreads to any adjacent roses through root entanglement.
Rose Rosette Disease was first identified in very contained situations during the 1940’s in Manitoba, Canada and in California. It got its name because new shoots from infected plants emerge with large clusters of buds and blooms instead of one blossom per stem, forming little bouquets, or “rosettes”. At the time of discovery, RRD was an obscure virus, and only one of many diseases that affected roses, so it didn’t raise any big alarms, though the prognosis was never good. Once a rose is infected, it has about two years before it dies. There is no mitigating treatment, no prevention and no cure. Trimming out infected branches is the botanical version of putting your head in the sand, as it only hides the disease from your view. It in no way stops, interrupts or even slows the spread of the disease nor the imminent death of the plant.
Back in the old days (from the 1940’s through the early 2000’s), any outbreak of Rose Rosette normally remained fairly contained for a couple of reasons that relate to one another. The first reason is that roses used to be really hard to grow. They were persnickety, prone to fungal diseases and pests, and therefore were not worth the trouble for the average gardener who typically passed on them in favor of sturdier alternatives. Avid gardeners who were willing to deal with black spot and more, took the challenge of growing roses, but these were mostly informed, dedicated gardeners who noticed and dealt with problems as they arose and did not allow diseases to run rampant and unchecked. So when an outbreak of Rosette Disease occurred, it was either easily contained within the parameters of the garden in which it occurred as attentive gardeners took action, or had a naturally finite life opportunity as these foolish little mites (exceedingly low on the food chain and not too bright) destroyed their own food source and were eventually taken out to the rubbish with their dead host.
The second reason Rosette was rare is that it is a “host specific” virus, meaning it does not effect plants other than roses. Thirdly, roses, historically being so high maintenance, were basically never planted in massive “monocultures” with the exception of rose gardens, within public botanical gardens which were very well cared for by highly competent gardeners. The final natural control was the eriophyid mite itself. This carrier is a minute little thing, one third to one quarter the size of other mites (which are already teeny weenie). Even if it could self-propel (which it can’t) it couldn’t get far, and with no power of self-locomotion and relatively few roses available, transportive winds mostly deposited them onto something other than a rose where it could not do any damage.
Enter Knockout Roses
All that changed with the advent of Knockout Roses. All of a sudden, in the year 2000, the rose world was turned upside down when a hybrid titan hit the market. Knockout Roses were resistant to black spot, powdery mildew and other fungal diseases as well as the pest problems typical of the roses of old. Knockout Roses, and subsequent landscape rose sisters such as Drift Roses, suddenly offered the average gardener a chance to have roses without the hassle and heartbreak of traditional rose maintenance. Now, even a garden with little or no attentive care could have the glory of roses. And what’s more, Knockout Roses made the singular, brief bloom time of roses a thing of the past. Knockouts bloomed consistently from early spring until the first freeze, which meant eight or even nine months of glorious roses in the most conducive zones. Banks and banks of Knockout Roses began appearing everywhere, including commercial campuses, parks, municipal gardens and even highway and median landscaping. The original vivid red single-bloom shrub became as ubiquitous as winter pansies and summer marigolds. Knockout Roses were a landscaping dream come true.
That is, until Rose Rosette reappeared
To be clear, Knockout Roses did not create Rose Rosette Disease and they are not more susceptible to it than any other roses. What they are is more plentiful. It is important to understand that the mite which carries the virus is carried on the breeze from one host to another. Therefore, proximity between infected plants and uninfected plants has been key to the spread of the disease. In other words, if there are no host plants within striking distance, the mites cannot reach another host plant, cannot lay eggs, cannot multiply and cannot send off more mites on the next breeze. This is why we must stop planting roses altogether for the time being. If we remove the host, we reduce the threat. It is impossible to eradicate the mite completely, and it is never a good idea to eradicate an entire species anyway. But if we remove the hosts temporarily, we can control the infestation and its spread.
What You Can Do
It is critical to remove roses at the first sign of infection and not replant. I personally feel that even uninfected roses should be removed from commercial and municipal gardens now, even if no sign of infection is yet evident because the vast mass, largely unattended plantings in wide, open spaces are particularly vulnerable to becoming hosts to this mite and creating a way- station for its spread. I know this is a very radical suggestion, but the seriousness of this infestation can not be overemphasized and commercial and municipal gardens are slow to notice and attend to plant disease problems when they show up, widening their impact and worsening their effect. Some gardeners, particularly those who live in very protected locations might be able to get through this unmolested. But what we are facing is a very serious horticultural problem. We need to take action now to prevent it from becoming a botanical catastrophe. I strongly feel that if we do not take strong steps to protect rose stock by removing the mass plantings which are perpetuating the spread of this disease, we could be facing the loss of the entire Rosa genus on this continent.
I have been advocating at wholesale nursery suppliers for several years now, asking them to stop stocking roses, but the reply I always get is, “People are still asking for them.” It is my position that as professionals in the industry, it is our responsibility to educate consumers. We must stop soft-selling the problem, we must stop thinking about short-term profit, and we must stop facilitating what could become the ultimate demise in this country of one of the world’s most beloved plants. It took a few years for Rose Rosette to devastate the rose population. It will take a few years without roses to control the problem. Then, as we begin to reintroduce roses into our gardens, we will need to do it judiciously with moderation instead of participating in a landscape feeding frenzy using a product that was, indeed, too good to be true.
About the Author
Rebecca Winn is the Owner and Lead Designer of Whimsical Gardens, a boutique landscape design firm specializing in high-end residential landscape designs. She is a recipient of the prestigious Texas Excellence in Landscaping Award (TEIL) through the Texas Nursery and Landscape Association for 2015 and again for 2016. She was the past garden writer for D Home magazine, and her book It’s Not My Garden, It’s My Life is due for release in 2017.
Winner 2015 Texas Excellence in Landscaping Award (TEIL)
Winner 2016 Texas Excellence in Landscaping Award (TEIL)
Artistic landscape designs studio: 972.661.2661