New method for the devitalization of imported horsetail (Equisetum hyemale)

Despite being rated as one of the world's worst weeds, Equisetum hyemale was until recently imported into New Zealand for use by the floristry industry, subject to devitalization. It was subsequently found that imported stems were not being successfully devitalized and importation was banned. This study, in two trials, used different dilutions of six herbicides, including Roundup, the one listed in the MAF Biosecurity NZ standard, to investigate if it were possible to render stems non-propagable without destroying their commercial use. This research found that a Sharpshooter (oryzalin) formulation at 1× and 1:2 dilutions of the field application strength was the only herbicide that completely devitalized the stem material with minimal impact on stem quality. Roundup at the concentration required by MAF Biosecurity NZ destroyed the stems, while 1:5 and 1:10 dilutions reduced the ability of the stems to be propagated, but still caused stem damage. AGPRO activated amitrole, Duplosan, Agritone and Kamba were not successful as devitalization agents.