5/9/01

Contacts:
John Obrycki, Entomology, (515) 294-8622
Robert Hartzler, Agronomy, (515) 294-1923
Daryl Frey, Iowa Department of Agriculture and Land Stewardship, (515) 281-8610
Susan Thompson, Ag Communications, (515) 294-0705

NEW PROJECT ADDRESSES MULTIFLORA ROSE INFESTATIONS

AMES, Iowa -- Multiflora rose was introduced in Iowa several decades ago -- promoted as a natural fence because of its dense, thorny nature. But it soon spread to areas it wasn't wanted, and has caused problems in pastures and recreational lands in the southern half of Iowa ever since.

In 1985, an Iowa Multiflora Rose Technical Advisory Committee was formed under the auspices of the Iowa Department of Agriculture and Land Stewardship to look for solutions. But solutions have been hard to find.

Last year, the committee turned to Iowa State University for help. The ISU Ag Experiment Station committed $17,000 to fund a new research project that gets underway this summer. Iowa State researchers John Obrycki, entomology, and Robert Hartzler, agronomy, will coordinate the effort. 

Managing the weed with herbicides is costly, and can have serious effects on nearby trees. The best control measure seems to be a natural enemy - rose rosette disease (RRD), which can cause the death of a multiflora rose plant in two to five years.

This isn't the first time Iowa State has turned its attention to multiflora rose. Earlier work showed RRD occurs throughout most of Iowa. Even though RRD is known to infect domesticated roses, only two specimens of flowering roses showing symptoms of RRD were submitted to the ISU Disease Clinic during a seven-year study period.

The primary concern about the use of RRD for biological control of multiflora rose is the possible effects on domesticated roses. "Yet as long as high densities of multiflora rose occur in Iowa, there will be a natural reservoir of RRD to infect domesticated roses," Hartzler says. "So the reduction of multiflora rose densities should be a common goal for rose growers and landowners."

That common goal was discussed at a meeting in January between Iowa State officials and representatives of rose growers associations. In the past, rose growers generally opposed projects that involved spreading RRD in an effort to control multiflora rose. But the meeting earlier this year led to an agreement that this new project should move forward.

Obrycki says even though ISU researchers have learned a great deal about RRD and multiflora rose during the past decade, several important questions remain. "For example, RRD is caused by an unidentified agent and is spread by an eriophyid mite. But the role of the mite in the spread of RRD is unknown," he says.

The first step in this new project is to survey the prevalence of RRD and the distribution and density of multiflora rose in the state. Ten fields in each of four counties in southern Iowa will be selected for the survey. Two sections of each field will be marked off, and the number of multiflora rose plants and the number of plants infected with RRD will be counted. Similar counts will be done annually for five years.

Once the first survey is complete, some sites where multiflora rose plants aren't infected with RRD will be chosen for the second part of the project. On these sites, an attempt will be made to infect multiflora rose plants with RRD by placing stems of infected plants near healthy plants. The progression of disease symptoms will be monitored.

One criteria for choosing these test sites will be that there are no known plantings of ornamental roses within one mile. Selected ornamental roses in the area will be monitored for RRD symptoms.

"If these releases result in enhanced spread of RRD and a reduction of multiflora rose densities, we will initiate an extension program to promote the release of RRD at selected sites in southern Iowa," Obrycki says. "At the same time, we'll outline the steps necessary to ensure the safety of nearby ornamental roses."

Daryl Frey, director of the laboratory division at the Iowa Department of Agriculture and Land Stewardship, provides administrative support to the Iowa Multiflora Rose Technical Advisory Committee. "I'm very pleased Iowa State has decided to begin this project. We need to gain an understanding of the prevalence of rose rosette disease in southern Iowa pastureland and augment this disease to reclaim these pasturelands for economic use," Frey says.

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