Response of black swallowwort (Vincetoxicum nigrum) to herbicides plus mowing

Authors: Milbrath, Lindsey; Biazzo, Jeromy; MORRIS, SCOTT - Cornell University; DITOMMASO, ANTONIO - Cornell University

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2023
Publication Date: 2/22/2023
Citation: Milbrath, L.R., Biazzo, J., Morris, S.H., Ditommaso, A. 2023. Response of black swallowwort (Vincetoxicum nigrum) to herbicides plus mowing. Invasive Plant Science and Management. 15:161-167. https://doi.org/10.1017/inp.2022.27.
DOI: https://doi.org/10.1017/inp.2022.27

Interpretive Summary: Black swallow-wort (Vincetoxicum nigrum) is a European twining vine that was introduced into eastern North America. Herbicidal control is a potentially effective management approach but has not yet been studied for black swallow-wort. Black swallow-wort was either sprayed with broad-spectrum herbicides at flowering in early July or mowed in early July followed by an herbicide application in late August, and the experiment was repeated over two years. We sprayed 2% solutions of glyphosate (two products) and triclopyr (one product). Both glyphosate products greatly reduced black swallow-wort biomass as well as black swallow-wort cover and stem densities, but mowing did not always increase the effectiveness of the treatments. Triclopyr was not effective in our study. Repeated, single applications of glyphosate can be useful for the management of black swallow-wort, but higher rates and possibly more frequent applications of triclopyr will need to be assessed to determine if triclopyr can be used for the control of black swallow-wort.

Technical Abstract: The invasive vine black swallowwort [Vincetoxicum nigrum (L.) Moench = Cynanchum louiseae Kartesz & Gandhi, Apocynaceae] 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 County, NY, USA. Experimental plots were either herbicide treated in early July or mowed in early July and subsequently herbicide treated in late August for 2 yr with the potassium salt of glyphosate (2.02 kg ae per ha), the isopropylamine salt of glyphosate (1.35 kg ae per ha), or the butoxyethyl ester of triclopyr (1.79 kg ae per ha). Both 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.