Influence of adjuvants on tetrapion efficacy for nassella tussock (Stipa trichotoma Nees) control and subsequent seedling establishment: a preliminary study

Nassella tussock (Stipa trichotoma Nees) is a perennial grass weed that seeds prolifically, resulting in build-up of a large soil seed bank. Due to it's vigorous growth it has the potential to spread rapidly in disturbed environments and overgrazed areas. Field trials were initiated in a dense nassella tussock infestation to assess the influence of various adjuvants (Citowett, Frigate and Reverseal 9) on the herbicide activity of tetrapion (sodium 2, 2, 3, 3-tetrafluoropropion) and to monitor subsequent seedling establishment. Reverseal 9 was the only adjuvant that significantly increased the efficacy of tetrapion at 0.44kg ai ha1, but this level of control achieved (75%) was not considered adequate for large-scale nassella tussock control operations. The next higher rate of tetrapion (0.88 kg ai ha1) was effective in achieving nearly total mortality (98%) with or without the addition of Reverseal 9. This rate also restricted establishment of nassella tussock seedlings for up to 23 months after initial ap...