Dioscorea oppositifolia (herb, vine, climber)

Ecology Distribution Management Info Impact Info References and Links Contacts

Management Information Preventative measures: Tu (2002) states that as with all prolific invaders, the key to the successful control of D. oppositifolia is to prevent new infestations or to control them as soon as possible. In North America, it has a wide range of environmental adaptability and few pests and predators. It has a high degree of asexual reproductive vigor, and is difficult to manage once firmly established. The use of manual and mechanical methods followed by another control technique (for example, periodic herbicide sprays to control for new bulbil recruitment and root sprouts) for several years should be accompanied by active restoration efforts to obtain desired results. Physical: Manual and/or mechanical methods of plant removal can effectively control small isolated patches. These methods, however, are extremely time and labour-intensive, as the large, deep tuber makes manual removal very difficult. All pieces of the tuber must carefully be removed or resprouting may occur. The removal of aboveground biomass appears to eventually exhaust the tuber, and indicates that perhaps a management regime of repeated grazing or burning may also work to kill the plant. These other methods, however, have not been tried. Manually picking the aerial bulbils off the vines will not kill the plant, but will prevent the further spread of D. oppositifolia for a growing season. Once the bulbils have dispersed, hand-pulling the young germinating bulbils from soil can be an effective control measure if the entire bulbil is removed (K. Johnson, pers. comm., in Tu, 2002). Although there are no conclusive results reported from long-term fire effects on D. oppositifolia yet, Kristine Johnson of the Great Smoky Mountains National Park has noted that sites burned in a wildfire from the previous fall had reduced amounts the following year. Chemical: Herbicide application appears to be the most effective means to control large infestations. One application of some herbicides can effectively kill all new germinating bulbils, but repeat treatments are probably necessary to completely kill large underground tubers that originally supported large mature vines. The herbicides glyphosate or triclopyr have been the most successful at killing the weed. Glyphosate also significantly lowered rates of plant growth from germinated bulbils as measured by stem length and numbers of leaves. Biological: There are currently no available biocontrol agents for D. oppositifolia. Snails and caterpillars have been observed browsing on leaves of this species, but do not appear to damage the plants significantly. Rodents and other small mammals also consume the bulbils, but the degree of consumption and damage to the plants has not been quantified (Beyerl 2001). The exact species of these consumers have not been determined, nor has it been elucidated if they are specifically feeding on D. oppositifolia or are only generalist feeders.              Location Specific Management Information North Carolina According to Kristine Johnson (in Tu, 2002), the Supervisory Forester at the Great Smoky Mountains National Park in eastern Tennessee and western North Carolina, the herbicide Garlon 4®, applied at 2% with an adjuvant, worked well to control D. oppositifolia. The timing of application is very important, with the best control achieved by spraying late in summer on foliage. Follow-up treatment is necessary, and herbicide or hand pulling of young germinants from bulbils works well if the entire bulbil is removed. Ohio In southern Ohio, constant mowing or clipping D. oppositifolia at the base of the vine (top of the tuber) appears to eventually kill it (Peter Whan of TNC’s Edge of Appalachia Preserve System, in Tu, 2002). Tennessee According to Kristine Johnson (in Tu, 2002), the Supervisory Forester at the Great Smoky Mountains National Park in eastern Tennessee and western North Carolina, the herbicide Garlon 4®, applied at 2% with an adjuvant, worked well to control D. oppositifolia. The timing of application is very important, with the best control achieved by spraying late in summer on foliage. Follow-up treatment is necessary, and herbicide or hand pulling of young germinants from bulbils works well if the entire bulbil is removed.          Management Resources/Links 1. Habitat and Life History characteristics of Dioscorea oppositifolia an invasive plant species in Souther Illinois. [Accessed 30 Dec 2003]         Summary: Detailed report on description, distribution, dispersal methods, impacts, habitats and control. 2. SEPPC (Southeast Exotic Pest Plant Council). Undated. Exotic Plant Management Plan         Summary: Summary of description, origin, similar species, habitat and control. 3. Tu M. 2002. Element Stewardship Abstract for Dioscorea oppositifolia L.. The Nature Conservancy.         Summary: An Element Stewardship Abstract containing detail report on description, distribution, dispersal methods, impacts, habitats and control.          Results Page: 1