The rise and fall of an invasive estuarine grass

  • Published source details Riddin T., van W.E. & Adams J. (2016) The rise and fall of an invasive estuarine grass. South African Journal of Botany, 107, 74-79.


This study is summarised as evidence for the following.

Action Category

Use herbicide to control problematic plants: brackish/salt marshes

Action Link
Marsh and Swamp Conservation
  1. Use herbicide to control problematic plants: brackish/salt marshes

    A before-and-after study in 2009–2015 in an estuary in South Africa (Riddin et al. 2016) reported that within three years of spraying invasive smooth cordgrass Spartina alterniflora with herbicide, native salt marsh plants had colonized. Herbicide application began in 2011. In October 2014, the first seedlings of native salt marsh plants appeared. In November 2015, 49 of 60 former cordgrass patches contained native salt marsh plants with up to 95% total cover. The total area of smooth cordgrass in the estuary was 10,221 m2 in 2011, then only 10 m2 in 2015. The above-ground biomass of smooth cordgrass within patches was 933 g/m2 in 2009, then only 240 g/m2 in 2015. Methods: From 2011, smooth cordgrass in the Great Brak Estuary was sprayed with herbicide. Intense treatments began in January 2013, with 2–3 applications each summer of glyphosate (10 kg/ha) and 0.5% imazapyr (100 g/L). Before 2014, herbicide was broadcast over cordgrass patches. From 2014, herbicide was applied to individual cordgrass plants. Between 2009 and 2015, cordgrass patches were mapped. Vegetation was also surveyed in living (pre-treatment) or dead (post-treatment) cordgrass patches (details not clearly reported for all surveys). Biomass was dried before weighing.

    (Summarised by: Nigel Taylor)

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