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Rose rosette disease showing up in more Georgia gardens

Posted: July 21, 2013 - 12:02am

Rose rosette disease is a viral disease that is becoming increasingly more common in Georgia. Extension agents throughout the state seem to be receiving more samples of infected roses.

Tiny eriophyid mites spread the disease from plant to plant. The disease only affects roses, and most species and cultivars are believed to be susceptible. Disease symptoms can vary depending on species and cultivar of rose. According to Alabama Extension Pathologist Jim Jacobi, the most common symptoms include: ‘witch’s brooms’ or abnormal clustering of small branches, distorted leaf growth, reddening of leaves, rapid stem elongation, stems that are thicker than parent stems, excessive thorn production and pliable thorns.

In the early stages, a diseased plant may exhibit a few of these symptoms. By the time symptoms are severe and recognizable, the disease is likely to have already spread to neighboring plants.

The disease was first discovered in the 1940s. Over the years, the eriophyid mite was known to be the transmitting agent, but the disease-causing agent was not discovered to be a virus until 2011. Rose rosette disease can be difficult to diagnose because it mirrors some symptoms of herbicide damage from chemicals like glyphosate (Roundup) and 2,4-D.

Multiflora roses are known to harbor the disease. Multiflora roses were introduced to the eastern United States in the 1800s from Japan and are now considered invasive. They have leaves with 5-11 leaflets, white flowers and bare red fruit. They can often be found in woodlands surrounding home sites. If there are any multiflora roses near the landscape, remove these plants if possible. Again, they are considered invasive and serve as a host for the disease.

Unfortunately, there is no cure for roses infected with rose rosette disease. Infected rose bushes, including roots, should be pulled up and removed. Burning the infected plant or placing in the trash are options for removal.

After removing infected plants, surrounding plants may be treated to help reduce mite populations that spread the disease. An insecticide such as bifenthrin should help control mites. However, eriophyid mites are small, so complete leaf coverage of sprays is essential. Also, most bifenthrin label directions call for application every two weeks from April to October.

There is research being conducted at several universities to find potential disease-resistant roses. Because scientists have isolated the virus responsible for rose rosette disease, quick-test kits will hopefully become available in future years for positive identification on-site.

If you think you have a rose bush infected by the disease, bring in a sample to the office or send me some pictures via e-mail. Early identification and plant removal can be the difference between losing one or all of the roses in the landscape.

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