EFFECTS OF TIME AND RATE OF APPLICATION OF HERBICIDES ON SERRATED TUSSOCK (NASSELLA-TRICHOTOMA) AND IMPROVED PASTURE SPECIES .2. TETRAPION

The effects of time and rate of application of tetrapion on burnt and unburnt serrated tussock, growing with and without improved species, were measured in four experiments carried out near Bathurst, New South Wales, between 1975 and 1978. Tetrapion proved effective in killing unburnt serrated tussock when applied in each season of the year. The most economical rates proved to be 1.00 kg a.i, ha-1 in spring and summer and 1.33 kg a.i. ha-1 in autumn and winter. Tetrapion was also effective in killing serrated tussock that had been burnt six and nine months before spraying. Although tetrapion had harsh phytotoxic effects on Phalaris aquatica and Trioflium repens growing in association with serrated tussock, these improved species recovered. Thus it proved possible to selectively remove serrated tussock from P. aquatica and T. repens by using tetrapion. Based on 1979 costs, tetrapion appears an economic alternative to other herbicides currently used to kill serrated tussock. © 1979 ASEG.