Response of Vincetoxicum nigrum (Black Swallowwort) to Herbicides plus Mowing


 The invasive vine Vincetoxicum nigrum (L.) Moench is difficult to control and herbicide studies are lacking. This long-lived perennial species is primarily found in high light environments in natural areas and perennial cropping systems in northeastern North America. We conducted a 3-yr herbicide efficacy study, with or without mowing, in an old-field site infested with V. nigrum in Dutchess Co., NY, USA. Experimental plots were either herbicide treated in early July or mowed in early July and subsequently herbicide treated in late August for two yr with the potassium salt of glyphosate (2.02 kg ae ha-1), the isopropylamine salt of glyphosate (1.35 kg ae ha-1), or the butoxyethyl ester of triclopyr (1.79 kg ae ha-1). Two glyphosate formulations were effective in reducing V. nigrum aboveground biomass although they were somewhat less effective in reducing cover or stem densities of V. nigrum plants > 10 cm tall after 2 yr compared with untreated plots. Mowing did not always enhance the efficacy of foliar glyphosate applications. Triclopyr, with or without mowing, was generally not effective against V. nigrum in our study. The only significant effect of triclopyr was to increase the cover of grasses in the plots. While annual applications of glyphosate can be useful for management of V. nigrum infestations, higher rates and more frequent applications of triclopyr need to be investigated to determine its usefulness for V. nigrum control.