Rose Rosette Virus
Searcy, Ark. –
Rose rosette is a lethal disease of roses that causes an array of relatively characteristic symptoms. The disease is usually first noticed in early summer at or near the ends of fast growing shoots. However, some people who are out pruning roses are seeing the symptoms from last year.
Typically, a witches’ broom symptom is produced with a proliferation of succulent, usually red-tinged, fast growing shoots emerging. These shoots often produce smaller, deformed leaves from stems that have a change in the number and structure of thorns.
The Knock Out roses and related shrub-type roses that were first introduced in 2000 are especially hard hit by the disease, and have been effectively killed out in many landscape plantings. Because the new shrub rose cultivars are so susceptible to the disease and were so widely planted, many people have tried to blame them for the reemergence of the problem. More than likely the disease is spread from the reservoir of infected wild multiflora roses to the garden.
In 2011, U of A virologist I.E. Tzanitakis and his graduate student Alma Laney published a paper that for the first time positively identified the virus responsible for the disease. Using genetic techniques, they positively identified the same virus from at least eight different states, positively identifying it in 84 of 84 infected plants and finding no trace of it in asymptomatic plants.
Since the 1980’s, it has been known that a microscopic eriophyid mite that lives in the growing tips of infected plants is the principle vector of the disease. These tiny mites are small enough that they spread on the wind currents and, when control recommendations are offered, it is against these tiny mites. There is no cure for the virus in prize roses so removal and burning is recommended.
While gardeners who have had rose rosette virus spread through their plants are no doubt frustrated, it is probably too early to count roses out. Not all roses are affected by the virus/mite combination so the ability to develop resistant clones is possible.
The mite that spreads the rose rosette virus lives on the top of the rose bush overwinter. Heavy pruning of the roses prior to new growth, and destroying the cuttings you take off, could help prevent the mite from surviving.
Our recommendation was that you did not ever need to prune Knockouts as severely as hybrid teas, saying a light shearing was fine. Now we are re-examining that, and recommending cutting all bush roses back to about ten inches or so in the dormant season--late February. If you have the wild mulitflora rose in your area, trying to eradicate that can also go a long way in getting rid of the mites, which breed there as well. Rose rosette is a virus that can attack all roses, and there is no cure once it gets it. Breeders are working on rosette resistant varieties, but so far haven't found any, but with proper pruning and good sanitation--removing plants when they have it, can help in the long run. I don't think we will ever see gardens without roses in them, or at least I sure hope not.
By Sherri Sanders
County Extension Agent - Agriculture
The Cooperative Extension Service
U of A System Division of Agriculture
Media Contact: Sherri Sanders
County Extension Agent - Agriculture
U of A Division of Agriculture
Cooperative Extension Service
2400 Old Searcy Landing Road Searcy AR 72143
(501) 268-5394
ssanders@uada.edu
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