7/15/96

CONTACTS:
Abraham Epstein, Plant Pathology, (515) 294-3807
Susan Anderson, Agriculture Information, (515) 294-0705

SEARCHING FOR BIOLOGICAL CONTROL OF MULTIFLORA ROSE

AMES, Iowa -- Researchers at Iowa State University are continuing studies on a biological means of fighting multiflora rose.

Dr. Abraham Epstein and co-researcher John Hill are exploring the use of rose rosette disease (RRD) as an effective and safe biological tool for controlling the spread of multiflora rose, a hardy plant in the rose family. Multiflora rose has invaded pastures in the southeastern two-thirds of Iowa. It was promoted in the Midwest in the 1930s as a pest- and disease-resistant cover crop, food for wildlife and a soil stabilizer.

Epstein is conducting research on multiflora rose and RRD at sites in ten Iowa counties. These sites include private farms, ISU Outlying Research and Demonstration Farms, U.S. Army Corps of Engineer property at the Lake Rathbun Reservoir and a Department of Natural Resources wildlife preserve. According to Epstein, properly managed RRD has greatly reduced the number of multiflora rose plants in plots at Lake Rathbun and several counties.

"We didn't get rid of the plant, but we certainly cut it down," Epstein said. "No biological control is 100 percent, whereas chemicals can kill non-target plants. RRD works selectively. That's one of the reasons it is so safe."

Epstein plans to expand field research this year by establishing new plots in at least six more counties with large populations of multiflora rose. Plots in farmers' pastures will be infected with RRD and compared with control plots for incidence of RRD.

To safely control the spread of RRD, researchers must identify its cause. They can use that information to develop a test to make sure other plants are not symptomless carriers.

Epstein and his team have determined RRD has some of the characteristics of a virus, but have not been able to isolate the organism that causes the disease. The Iowa Legislature and a group of rose producers have each allocated funds to get the project underway.

In 1993, four risk assessment plots were established to help determine whether augmented RRD affects ornamental roses. Ornamental roses were planted at varying distances from multiflora rose plants infected with RRD. Two of the plots were destroyed in the 1993 flood, and another was eaten by deer. Risk assessment continues at the fourth site in Lucas County, where 600 ornamental roses were planted in pasture plots.

"This is the fourth year of this study, and it appears the danger to ornamental roses is minimal because the mite that spreads RRD is relatively immobile and does not travel far," Epstein said. "It was found that no infection occurred beyond 100 yards. Incidence of RRD infection drops off very quickly with distance."

Epstein said as with any other plant disease, proper management is essential for the well-being of ornamental roses, but RRD can be managed.

RRD was found for the first time in Iowa in 1985. It can be spread not only by the mite, but also by grafting buds of diseased plants to healthy ones. RRD causes red, rapidly growing shoots that will kill a small plant in two years. Large plants may take four to five years to succumb.

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