Dioscorea oppositifolia (Chinese yam) is an exotic perennial vine invading natural areas in the temperate regions of the eastern United States. Rapid early-season growth of D. oppositifolia is facilitated by an extensive tuber system. Plants can reach heights greater than 370 cm, as the plants climb trees and other vegetation. Shoot length increased 3.6 cm/d from late May to mid-August under field conditions, and primary and secondary tuber length increased 0.28 and 0.2 cm/d, respectively. This indicated rapid vegetative growth and substantial food reserves to form new plants in subsequent years. Dioscorea oppositifolia plants also formed aerial bulbils of 0.8- to 1.2-cm diameter, which are important in dissemination of the species over geographical areas. A field study indicated incomplete control from manual removal, clipping by hand, or glyphosate (2% v/v) application to control D. oppositifolia, although glyphosate was the most effective. Additionally, the use of herbicides was more efficient from a time-utilization perspective than either manual removal or clipping. In a separate study, glyphosate application at flowering was more effective in reducing D. oppositifolia growth the year after application as compared with glyphosate applications soon after emergence. Under greenhouse conditions, however, glyphosate at 0.84 kg ae/ha provided <15% control. The ester formulation of triclopyr at 2.5 kg ai/ha provided >90% D. oppositifolia control. Metsulfuron provided 31% control, and mesotrione provided 36% control and at higher rates may reduce D. oppositifolia growth. Several other herbicides having diverse modes of action provided minimal control of D. oppositifolia.

Chinese yam is an exotic perennial vine that invades natural areas in the temperate regions of the eastern United States. Research was conducted from 2001 to 2004 to evaluate growth, reproduction, and management options for this weed. Vine length, lateral shoot production, and reproductive capacity were lower in the first year of growth compared to 2 subsequent years. During the second and third growing season, plants were more mature and tended to flower earlier and produce larger bulbils compared to the first growing season. Maximum vine length was not reached prior to frost in the first year and was approximately 480 cm in each of the subsequent years. Both glyphosate and triclopyr were effective in controlling plants growing from bulbils and plants growing from tubers. Triclopyr did not display acropetal translocation, in that only the treated tissue died. However, both products displayed excellent basipetal translocation resulting in elimination of tubers and no shoot regrowth the year following treatment. Native area managers should attempt to eradicate small populations of Chinese yam prior to establishment of an extensive tuber system.