Response of Pale Swallow-wort (Vincetoxicum rossicum) to Triclopyr Application and Clipping

Pale swallow-wort is a nonnative vine, invading natural areas across much of the northeastern United States and southeastern Canada. Control of this clump-forming herbaceous perennial has been difficult. We conducted a 2-yr study (2005-2006) in a heavily infested site in Chaumont, NY to assess the response of swallow-wort to triclopyr applied once as a foliar treatment (1.9 kg ae/ha) (2005 only) alone or in combination with clipping 4 wk later, followed by a single clipping in 2006. We also evaluated the response of swallow-wort to one or two clippings during each of the 2 yr. Two yr after treatments began, swallow-wort cover was lower in plots treated with triclopyr (20 +/- 5%) compared with plots subjected to clipping-only (56 +/- 6%) or unmanaged controls (76 +/- 6%). Stem densities were also lower in triclopyr-treated plots (25 5 stems/m(2)) than in clipping-only (188 +/- 9 stems/m(2)) and control (178 +/- 10 stems/m(2)) plots across three different sample dates. Seedling densities were lower in triclopyr-treated plots (160 +/- 50 seedlings/m(2)) relative to clipping-only (1,120 +/- 180 seedlings/m(2)) and control (960 +/- 50 seedlings/m(2)) plots after the 2005 growing season. The cover of other plant species was negatively correlated with swallow-wort cover and was higher in triclopyr-treated plots (75 +/- 3%) than in clipping-only (5 +/- 1%) and control (7 +/- 4%) plots in 2006. Across both years, swallow-wort in control and clipped plots produced follicles, but not in triclopyr-treated plots. Regardless of clipping frequency, clipping in June or July was not effective in reducing swallow-wort stem density, cover, or follicle production. Although a single application of triclopyr provided considerable suppression of swallow-wort after two growing seasons, application of triclopyr in subsequent years is likely required to achieve long-term control.