Invasive weed swallow-wort (Cynanchum acutum L.) response to chemical and mechanical practices.
Swallow-wort (Cynanchum acutum) is increasingly getting a problematic invasive weed in many parts of Iran and several countries around the world. Despite the extensive invasion of C. acutum, the efficacy of different mechanical/chemical treatments for its effective control has rarely been investigated. The objective of the present study was to explore the effects of mechanical weeding (brush cutter) and herbicide applications on C. acutum biomass and density at two locations (Abyek and Yazd) in Iran during a 3-year experiment. Treatments included: (a) no chemical/mechanical treatment, (b) glyphosate, (c) bromoxynil + MCPA, (d) mecoprop-p-dicloprop-p-MCPA, (e) triclopyr, (f) metribuzin, and (g) brush cutter. Results showed that glyphosate and triclopyr provided the highest efficacy in reducing C. acutum density and biomass relative to non-treated control according to most post-treatment assessments; although glyphosate showed more relative efficacy than triclopyr in reducing C. acutum density in Yazd at 1 year after retreatment and in reducing C. acutum biomass at both the locations at 1 year after treatment. It was shown that mecoprop-p-dicloprop-p-MCPA had statistically similar efficacy as glyphosate and triclopyr in reducing C. acutum density at most assessments. After retreatment, bromoxynil + MCPA at both the locations and mecoprop-p-dicloprop-p-MCPA in Abyek showed no statistically significant differences with glyphosate and triclopyr in terms of C. acutum biomass reduction. Metribuzin and brush cutter could not provide acceptable efficacy in C. acutum control. Overall, results indicated selective herbicides are also good chemical options for improving C. acutum management plans and decreasing this invasive weed damage.