Effect of mixtures of tetrapion and 2,2-DPA on the control of serrated tussock (Nassella trichotoma)

Abstract

Mixtures of tetrapion (sodium 2,2,3,3-tetrafluoropropionate) and 2,2-DPA (sodium 2,2-dichloropropionate) at rates of 1.125 + 5.2 and 0.75 + 10.4 kg/ha a.i. were applied to serrated tussock on six occasions between 1980 and 1983 and were equal to or superior to the recommended rate of tetrapion alone (1.5 kg/ha a.i.) or 2,2-DPA alone (20.8 kg/ ha a.i.) in killing serrated tussock. Although the mixtures of tetrapion and 2,2-DPA produced a much faster phytotoxic effect on serrated tussock than tetrapion alone, establishment of surfaces own pasture species was not improved by using the mixtures. The reasons for this result are discussed. Mixtures of tetrapion and 2,2-DPA may be useful on soils where residual effects of tetrapion remain for long periods, when quick phytotoxic effects will stop serrated tussock flowering or allow re-spraying to be carried out after 6 weeks rather than after 9-12 weeks with tetrapion alone, and where improved effectiveness on annual grass weeds is required. Establishment of surface-sown pasture species after use of tetrapion, 2,2-DPA, or the mixtures applied before the autumn break, was improved by killing annual weeds with glyphosate application 1 week before sowing in late autumn or early winter.