Herbicide control of exotic annual plant species in Acacia acuminata-Eucalyptus loxephleba woodland in south-western Australia and effects on native ground flora

Graham. W. Arnold, John W. Weeldenberg and Joe Leone, CSIRO Division of Wildlife and Ecology, Locked Bag No.4, Midland, Western Australia 6056, Australia.


Summary

The exotic annuals Avena fatua, Vulpia myuros, Erodium botrys, Hypochaeris glabra and Pentaschistis airoides are major invaders of Acacia acuminata-Eucalyptus loxephleba woodland. Two small plot experiments tested herbicides at two sites in 1990 for their control of exotic species without destroying the native species and were assessed at the end of the 1990 and 1991 growing seasons. The herbicides used were Assure®, Fusilade®, Fusilade plus Simatox®, Oust®, Roundup®, Sertin® and Surflan®. Only Oust gave good control of exotic dicots and monocots at both sites. There were some carryover effects in 1991 at site 1 where A. fatua was significantly lower on all herbicide treatments than on controls. Oust at 300 g ha-1 gave the best second year control of this species and of V. myuros but also eliminated native Crassula species. Nevertheless, in 1991 plots sprayed with both rates of Surflan, Oust and Roundup in 1990 had twice the cover of native species in control plots.

A further selection of herbicides were compared at another site in 1991. The herbicides were Assure, Atrazine®, Fusilade, Goal®, Oust, Sertin, Simatox and Sprayseed®. In the year of spraying, Goal came closest to the desired outcome of reducing exotic species without detriment to native species but it would have to be combined with a pre-emergence application of Simatox to eliminate the grass P. airoides and the dicot H. glabra. In 1992, there were no differences between any treatments and control plots in the proportions of exotic and native species. There were some differences in the composition of the native species.

It is concluded that herbicides can be used to eliminated certain exotic annual species with little damage to native herbaceous species. However, because of soil seed banks, application in just one year may not provide much carryover effect and so not allow native species to increase.

 

Plant Protection Quarterly (1998) 13 (1) 39-43.