Herbicides to replace flupropanate for the control of serrated tussock (Nassella trichotoma (Nees) Arech.)
M.H. Campbell and H.I. Nicol, NSW Agriculture, Orange Agricultural Institute, Forest Road, Orange, New South Wales 2800, Australia.
Experiments carried out in the southern tablelands of New South Wales from 1995 to 1999 to investigate possible herbicide replacements for flupropanate for killing serrated tussock (Nassella trichotoma (Nees) Arech.) showed that glyphosate was the only practical alternative available at present. However, results from applying rates within + or -0.20 kg a.i. ha-1 of the following, 0.45, 0.90, 1.35, 1.80, 2.25, 2.70 and 3.15 kg a.i. ha-1 to unburnt/ungrazed serrated tussock varied, respectively, from 0 to 81% kill, 0-91%, 0-99%, 75-100%, 78-100%, 80-100% and 93-100%. Effectiveness was favoured by dry conditions after spraying, shade, infertile soils and non-grazing. Because of the variable results recorded, recommendation of a minimum effective rate for all regions cannot be made. The most practical method of determining this rate is for producers or researchers to apply a range of rates from 1.0 to 3.0 kg a.i. ha-1, at 0.5 kg a.i. ha-1 intervals, over a number of years.
Results from aerial application of glyphosate indicated that it is effective in killing serrated tussock when applied by helicopter but at moderate and high rates trees would also be killed. The major disadvantage of glyphosate, damage to associated useful species, was reduced by applying it when the useful species were dormant. Overall spraying of serrated tussock in an introduced pasture resulted in re-infestation of 11 300 tussock seedlings ha-1 due to damage to the introduced species. To attempt to control these seedlings it would be necessary to re-sow the pasture after spraying.
Plant Protection Quarterly (2001) 16 (2) 69-74.