Prior to the last ten years, multiflora rose grew essentially "pest free" throughout most of its area of establishment in the eastern half of the United States. This freedom from destructive diseases, insects, or other kinds of biological pests enhanced its rapid spread from use as a rootstock in propagating ornamental roses and conservation plantings made in the 1940s and 1950s.
Presently, three biotic agents have become destructive pests on multiflora rose and show potential to provide eventual significant biological control. They are:
Most attention to date has centered on rose rosette disease, but the rose seed chalcid also may have major future impact in biocontrol.
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| Figure 16 | Figure 17 | Figure 18 |
Figures 16 through 18 show rose rosette disease (RRD) symptoms on multiflora rose. Symptoms include red and purplish vein mosaic, production of bright red lateral shoots, dwarfed foliage, and proliferated development of compact lateral branches to form "witches brooms." The disease is transmitted (vectored) by a tiny eriophyid mite (Phyllocoptes fructiphilus) that is widely and naturally found on roses throughout most of the country. On average, RRD-infested plants die within 2 years of infection, with a range of 1 to 4 years. This virus disease now is found within an area roughly bounded by Iowa and Wisconsin on the north; Texas on the south; California, Utah, and Wyoming on the west; and Maryland, Pennsylvania, and West Virginia on the east. Rose rosette disease is much more prevalent in some areas than others. This agent might eventually kill 93% of multiflora rose in the eastern United States as soon as it spreads further eastward. West Virginia researchers, however, have identified several insect and fungal predators of the RRD-vectoring mite. These, along with drought, low plant density, and extreme temperature changes all can adversely influence the rate of spread and intensification of RRD.
Rose rosette also can infect some but not all types of domesticated, ornamental roses. More information concerning this disease and its impact on both multiflora and domestic roses can be found in Iowa State University Bulletin PM-1532, Rose Rosette Disease.1 Efforts to introduce rose rosette disease into "new" areas by bud grafting have proven difficult. Research by Epstein at Iowa State University has defined the kinds of infestations where bud grafting may be most successful. Iowa State Bulletin PM-1615, Biological Control with Rose Rosette Disease1, contains color illustrations of grafting procedures and best patterns of use. Researchers there warn, however, not to expect significant incidence of new RRD infestations until the second or third year following grafting.
1. Iowa State Extension Distribution Center, 119 Printing and Publications Bldg., Ames, IA 50011-3171; phone (515) 294-5247.
Rose rosette was first found in Ohio in 1987 and by 1993 was detected widely across southern Ohio. In such locations, it is not necessary to refrain from chemical or mechanical controls to rapidly reclaim tracts for other purposes. Ample RRD-infected plants should exist nearby to perpetuate local intensification of this rose pathogen.
The rose seed chalcid (Megastigmus aculeatus var. nigroflavus) has been shown to be widely distributed where multiflora rose is found in the United States. The chalcid, more prevalent in eastern states than midwestern, is spread by birds and is catching up to the widespread distribution of multiflora rose. The small torymid wasp lays eggs within seeds, rendering them sterile. This biological agent is likely to spread and colonize all stands in possibly 20 or more years, eventually destroying the viability of 90% of yearly seed production. This would become a powerful biological control, especially where rose rosette is also present.
The rose stem girdler [Agrilus aurichalceus (Coleoptera: Buprestidae)] may be of lesser importance, but in concert with the others should further enhance biocontrol. The larvae girdle can kill individual canes, not whole plants. Developing rose hips (fruits) and seeds above the girdling will die. Amrine and coworkers at West Virginia University have found an abundance of rose stem girdler at sites in Indiana, Ohio, Pennsylvania, and West Virginia providing some degree of control.
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