Experimental control of exotic spiny rush, Juncus Acutus from Sydney Olympic Park: I. Juncus mortality and re-growth

Abstract

Two experiments were conducted in Badu Saltmarsh within Sydney Olympic Park to test the efficacy of methods for controlling and/or eradicating Spiny Rush (Juncus acutus), an exotic weed. The experiments were conducted over a period of 30 months, between March 2001 and September 2003. One experiment was based on the physical removal of J. acutus and the other on the application of Glyphosate and salt. The physical-based experiment had four treatments and the Glyphosate-based experiment had five treatments, including a control. Each of these nine treatments had three replicate quadrats, each 2m x 2m size; hence there were 27 quadrats in total. Including the pre-experiment data, systematic observations were made on 11 occasions at varying intervals. Observations were made on mortality, coverage, re-growth and seedling growth of J. acutus, weed and native saltmarsh vegetation coverage. Results indicated that by physically removing J. acutus and by transplanting the plots with native saltmarsh species, significantly faster colonisation of these native species was possible. Addition of J. acutus or traditional garden mulch effectively restricted J. acutus seedlings. The growth of J. acutus seedlings was very slow in mulched plots – only about 15cm in 30-months period. By applying Glyphosate (50:1) on the whole plant, even for a single application, it was possible to completely kill J. acutus. A single application of Glyphosate (50:1) on the cut bases of J. acutus did not restrict the re-growth of the J. acutus. J. acutus initially re-grew quickly from cut bases but then the growth rate slowed down remarkably, reaching about 50cm high in 30 months. All the treatments were effective in controlling J. acutus but the efficacy varied largely between the treatments. It was concluded that a combination of two or more methods might be the best approach for tackling J. acutus.