Use of low rates of flupropanate for serrated tussock control

M. H. Campbell, NSW Department of Primary Industries, (Retired)

A paper presented at the 2006 Grassland Society of NSW Conference (Nicholls 2006) reported that flupropanate killed serrated tussock on a property near Gunning NSW but it also killed associated useful species.

The flupropanate was applied to serrated tussock growing on infertile soil derived from slate and shale at a recommended rate of 2 L/ha of product (75% a.i.).

It has been known for many years that rates lower than 2 L/ha will kill serrated tussock on infertile soils and cause less damage to associated useful species..

For example, the 2 L/ha rate needed to kill serrated tussock on fertile basalt soils was deemed too high for killing serrated tussock on less fertile soils derived from granite, slate or shale; here 1 to 2 L/ha have proven effective (Campbell 1983, 1995).

The distribution of information on low rates is restricted and that is why producers new to serrated tussock use high rates recommended on the label and elsewhere.

In the supplement to the NSW Department of Primary Industries Agfact of 1995 (Campbell 1995) information on the use of low rates was presented. However, later Agfacts did not have supplements that discussed the rates of herbicide to use on soils of varying fertility. Thus information on low rates is difficult to access.

Low rates of flupropanate can be used under the authority of Permits. For example, rates from 1.0 to 2.0 L/ha were used on the Monaro under the provision of a Permit and rates from 1.5 to 2.0 L/ha can be used under Permit 9198 at present.

The above information is now available in the Third Edition of the Environmental and Noxious Weed Control Handbook from NSW Department of Primary Industries.

In general, applying rates of flupropanate lower than 2 L/ha is permissible without a Permit but they are not covered by the manufacturer’s warranty.

The effective low rate to apply on a particular property needs to be determined by trial and error by the producer to ensure a reliable kill.

Flupropanate is more effective at low rates when applied in spring or summer than when applied in winter.

As has been emphasised for many years, the use of herbicides for killing serrated tussock should go hand in hand with pasture improvement/management (Campbell 1962).

This can be done by sowing improved pasture species after spraying or by selectively removing serrated tussock from improved or native pastures.

Serrated tussock can be selectively removed from phalaris, cocksfoot or fescue pastures with flupropanate (Campbell 1979, 1997). It can also be removed from pastures containing sub clover by applying it in late spring, however, it will severely damage the clover if applied in autumn or winter.

Serrated tussock can be selectively removed from red grass, kangaroo grass or poa tussock pastures by using flupropanate. For example, a 40 ha hillside on the Abercrombie River aerially sprayed with 1.75 L/ha flupropanate in 1995 reduced the serrated tussock ground cover from 75% to 8% by 2004. Over the same period the ground cover of red grass increased from 10% to 65%.

This hillside was grazed lightly with sheep but no spot spraying was undertaken and no superphosphate or subterranean clover applied. Had the latter been done production would have been increased and control of serrated tussock enhanced.

Some native grasses are killed by flupropanate even at low rates, the most important being Wallaby grass and Weeping grass.

Flupropanate will kill useful species if it is applied at very high rates. The danger is greatest when spot spraying because, given the same mixture of herbicide to water, some sprayers spray tussocks quickly while others spray slowly. Tests on the southern tablelands of NSW revealed that rates of flupropanate varied from 1 to 17 L/ha depending on the spraying speed of the operator.

Naturally, when extremely high rates are applied almost all plants are killed.

In some cases, operators add extra herbicide above the recommended rate to ensure a kill. This is not necessary with flupropanate.

Conclusion: More information should be made available to producers on the use of low rates of flupropanate so its selectivity can be maximised.

Campbell, M. H. (1962). Kill serrated tussock with chemicals. Agricultural Gazette of NSW. 73, 626.

Campbell, M H. (1983). Review of the present state of knowledge of the effect of flupropanate on serrated tussock. NSW Department of Agricultue, Flupropanate Update Seminar, Bathurst.

Campbell, M. H. (1995). Serrated tussock control. NSW Department of Agriculture Agfact P7.6.30, Herbicide Supplement.

Campbell, M. H. (1979). Selective removal of serrated tussock from a phalaris pasture. Proceedings 7th Asian-Pacific Weed Science Society Conference. 129-30.

Campbell, M. H. (1997). Effect of low rates of flupropanate on selective removal of serrated tussock seedlings from a young improved pasture. Plant Protection Quarterly. 13, 80-6.

Nicholl, A. (2007). Conquering serrated tussock at “Yellanglo”. Proceedings Grassland Society of NSW 21st Conference, Wagga Wagga. 33-5.