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Multiflora Rose: The Mixed Blessings of Rose Rosette Disease

Posted: July 30, 2013

Multiflora rose is an invasive species, but it is now under attack from a virus.

Increasingly across Pennsylvania, it seems that the ubiquitous patches of multiflora rose are displaying symptoms of rose rosette disease. This disease, first described in Canada, California, and Wyoming in the 1940s, has slowly worked its way across the range of introduced multiflora rose. Landowners and managers who have battled this invasive plant for years celebrate; rose growers lament.

Multiflora rose was brought to North America in the 1700s from Asia as rootstock for grafting ornamental roses. It was not too long, though, before it was recognized for other values. From the 1940s through the 1960s, many conservation agencies touted the “living fence” for its many benefits. For sure, planted along pasture margins it kept cows and horses confined. But more importantly, here was the ultimate conservation plant. It was easy to grow; it grew well almost anywhere – even strip mines. It held the soil. It provided plentiful and nutritious hips. It created wonderful dense wildlife habitat. Many wildlife species flourished with its presence. Some departments of transportation thought the tangles of thorns were useful as crash barriers.

Before too long, though, it was apparent that multiflora rose had the potential to dominate landscapes with its rapidly growing canes. As the name multiflora implies each rose bush is capable of producing hundreds if not thousands of rose hips, and each of these hips contains, on average seven seeds. These highly viable seeds can lay dormant for a long time, up to at least twenty years, waiting for the right conditions to germinate. Birds and other animals that readily eat the hips can quickly spread the seeds across the landscape.

Fortunately or unfortunately, rose rosette disease is becoming more common. It has slowly spread through native, wild, and multiflora rose populations arriving in southwestern Pennsylvania sometime in the 1990s. Researchers at the University of Arkansas finally isolated the Rose rosette virus in 2011, although it had been present for many years. The disease moves by an eriophyid mite or by grafting, and multiflora rose is very susceptible. Mite populations are lowest in the spring and build through the summer, becoming most abundant in September. Here is the challenge: cultivated roses planted downwind of infected multiflora rose are especially at risk when wind currents move mites. Once infected, roses can show signs of the disease in as few as four weeks. There is no known treatment or cure for infected plants.

Rose rosette disease has many symptoms. It is most often recognized by a rapid elongation of new shoots, which often form clusters of small branches or “witches brooms. The leaves on these brooms are often small, distorted, and often red in coloration. The canes where brooms occur will often be soft and pliable, even the thorns have these characteristics, at least for a while. Flowers forming on these canes may also display deformities. Infected plants often die in one or two years; however, some plants may live as long as four years. Some researchers report that infected canes are more susceptible to damage from low temperatures.

While some landowners will celebrate the loss (reduction) of multiflora rose. Its loss is not a reason to reduce vigilance. At least one study has shown that the void left by its demise is rapidly filled by bush honeysuckle and, perhaps, autumn or Russian olive. Some people suggest that we give up the fight against burgeoning invasive plants; others argue that we have to encourage more indigenous plants to support native insects, which feed our native species. If you want to keep invasive plant species at bay on your land, the sooner your act, the better. It is much easier to control a few plants.

The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management. For a list of free publications, call 800-234-9473 (toll free), send an email to RNRext@psu.edu, or write to Forest Stewardship Program, Natural Resources Extension, The Pennsylvania State University, 416 Forest Resources Building, University Park, PA 16802. The Pennsylvania Bureau of Forestry and USDA Forest Service, in Partnership with Penn State’s Department of Ecosystem Science and Management sponsor the Forest Stewardship Program in Pennsylvania.