Madalyn Shires, Extension Graduate Student, Department of Plant Pathology and Microbiology*
Many viruses cause diseases with mosaic-type symptoms in crop and horticultural plants. In the United States, these mosaic diseases commonly appear on beans, peppers, potatoes, roses, tobacco, and tomatoes. Although the disease doesn’t kill rose plants, effects of infection reduce vigor, shorten lifespan, stunt growth, and weaken the plant so it cannot survive the stress of transplantation or winter injury.
Several viruses cause mosaic disease symptoms in roses—Prunus necrotic ringspot virus (PNRSV), apple mosaic virus (ApMV), and Arabis mosaic virus (ArMV). These viruses can affect roses separately or in some combination, a trait known as a virus complex. Rose mosaic virus complex (RMVc) is often a more accurate designation than the more common name rose mosaic virus (RMV) because it takes into account that several viruses are present in the plant and causing the disease symptoms. Mosaic disease caused by RMVc is one of the most widespread rose diseases in the United States and occurs with many rose varieties.
Rose mosaic disease appears in the spring, usually only on a portion of the plant (Fig. 1). It is easy to miss or mistake symptoms because they show up early in the season on the first sets of new growth and become obscured by subsequent growth. Typical symptoms are ring spots,chlorotic line patterns (Fig. 2), watermarking (Fig. 3), and leaf mottling. Yellow net and yellow mosaic patterns can also develop.
Infection by the PNRSV virus can cause leaf mottling.Vein banding, often seen in roses infected with both PNRSV and ArMV, can occur with PNRSV-only infections, especially during long periods of high temperatures. In some cultivars, RMVc causes a color-breaking, mottled effect in flowers.
A typical mode of disease transmission is through grafting diseased tissue or buds onto diseased rootstock. This disease is unlikely to spread via contaminated pruning tools, insect vectors, or plant-to-plant irritation (plants rubbing against each other). Once inside the host, the virus travels to the roots, becomes systemic, and moves throughout the entire plant. The concentration of the virus can vary and may not be uniformly distributed. When not evenly dispersed throughout the plant, the virus causes varying symptoms or sometimes even a lack of symptoms.
Because there is no cure, it is important to prevent the disease from establishing in the first place. Be sure to purchase only healthy-looking plants and avoid more susceptible varieties such as Queen Elizabeth and Madame Butterfly.
After the onset of symptoms, pruning infected tissue won’t cure the disease because the virus will have already spread throughout the entire plant. The best solution is to remove and properly destroy infected plants by bagging all plant tissue and digging up the rose bush. However, since an infected plant does not pose a risk to other plants, you don’t have to remove it immediately. For disease confirmation, submit a symptomatic plant sample for diagnostic analysis.
Goldberg, Natalie. 2006. Rose Mosaic Virus. O & T Guide, OD-9. New Mexico State University, College of Agriculture and Home Economics, Cooperative
Extension Service: http://aces.nmsu.edu/ces/plantclinic/ documents/rose-mosaic-virus-_od-9__final.pdf.
Horst, Kenneth and R. Cloyd. 2007. Compendium of Rose Diseases and Pests, 2nd ed. The American Phytopathological Society, 32–34.
Secor, Gary, et al. 1977. “Rose Virus and Virus-Like Diseases.” California Agriculture. Department of Plant Pathology, University of California-Davis: https://ucanr.edu/repositoryfiles/ca3103p4-63242.pdf.
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