Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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RESPONSE OF PALE SWALLOW-WORT TO TRICLOPYR APPLICATION AND
CLIPPING. K.M. Averill, A. DiTommaso, and S.H. Morris, Cornell Univ., Ithaca, NY.
ABSTRACT
Pale swallow-wort (Vincetoxicum rossicum (Kleopow) Barbar.) is an invasive
alien vine in natural areas in many Northeastern U.S. States and Provinces of Ontario
and Quebec. Since effective control of this herbaceous perennial has been previously
difficult, we conducted a two-year (2005-2006) triclopyr and clipping field study in
Chaumont, NY. We compared the effects of a single season (mid-June 2005) foliar
application of triclopyr at the labeled rate of 1.9 kg a.e. ha -1 , alone and in combination
with clipping of aboveground tissue (mid-July), and the effects of clipping once (mid-
June) and twice (mid-June and mid-July) during the first and second seasons on pale
swallow-wort stem and seedling density and percentage cover. By the end of
September 2005, pale swallow-wort stem densities were significantly lower in triclopyrtreated
plots (0.43 to 13 stems m -2 ) than in clipped-only (181 to 206 stems m -2 ) and
unmanaged control (167 stems m -2 ) plots. Similarly, the percentage cover of pale
swallow-wort was significantly lower in plots treated with triclopyr (6 to 13%) compared
with plots subjected to clipping only treatments (76-85%) or unmanaged control plots
(78%). By the end of September 2005, the percentage cover of other plant species was
significantly higher in triclopyr treatments (66 to 67%) than in the clipping only
treatments (11-16%) and in the unmanaged control (11%). The same differences in
stem density and percentage cover were observed through August 2006. Seedling
densities of pale swallow-wort varied by year and treatment. Densities were significantly
greater in the clipping only and control treatments in 2005 (964 to 1207 seedlings m -2 )
than the same treatments in 2006 (414 to 493 seedlings m -2 ), but they were not
significantly different in the triclopyr treatments between 2005 (114 to 207 seedlings m -
2 ) and 2006 (111 to 254 seedlings m -2 ). By the end of both the 2005 and 2006 growing
seasons, in clipping only plots mature follicles were produced, however in triclopyrtreated
plots no follicles were produced. Thus, the clipping only treatments, regardless
of frequency, were not effective in reducing pale swallow-wort aboveground biomass,
cover, or follicle production. The timing of clipping may be critical in reducing follicle
production and, although further assessments are necessary, a later-season (August)
clipping may be more effective. Although in this study a single application of triclopyr
provided considerable control of pale swallow-wort even after two growing seasons, it is
likely that repeat applications of triclopyr during multiple years would be required to
achieve effective control, especially in heavily infested areas.
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