Biology, Ecology and Management of the Invasive Navua Sedge (Cyperus aromaticus)—A Global Review

Abstract

Navua sedge (Cyperus aromaticus (Ridley) Mattf. & Kukenth) is an invasive perennial sedge, native to tropical Africa, which is threatening many natural ecosystems and agroecosystems, especially in northern Queensland, Australia. Crop and pasture production have been impacted by Navua sedge and it is also directly causing reductions in dairy and beef production in affected regions. This review documents the biology, ecology and potential management options to minimise the spread and impact of Navua sedge. The weed reproduces both sexually (seeds) and vegetatively (via underground rhizomes). Its tiny seeds can be spread easily via wind, water, vehicles, farm machinery and animals, whilst the rhizomes assist with establishment of dense stands. The CLIMEX model (which uses distribution and climate data in native and novel ranges) indicates that in Australia, Navua sedge has the potential to spread further within Queensland and into the Northern Territory, New South Wales and Victoria. Several management strategies, including mechanical, chemical and agronomic methods, and their integration will have to be used to minimise agricultural production losses caused by Navua sedge, but most of these methods are currently either ineffective or uneconomical when used alone. Other management approaches, including biological control and mycoherbicides, are currently being explored. We conclude that a better understanding of the interaction of its physiological processes, ecological patterns and genetic diversity across a range of conditions found in the invaded and native habitats will help to contribute to and provide more effective integrated management approaches for Navua sedge.

Soil Seed Bank Dynamics of Pastures Invaded by Navua Sedge (Cyperus aromaticus) in Tropical North Queensland

“…Navua sedge is a clump-forming, creeping rhizomatous sedge growing up to 1 m in height (occasionally up to 2 m), with densely packed tillers. Lanceolate leaves are generally clustered at the base of the plant with each leaf about 15 cm in length and 3-5 mm in width (Shi et al, 2021). Five to eight leaf-like bracts subtend the flowers at the apex of the tiller (Shi et al, 2021).…”

“…A native of equatorial Africa, this species has now been introduced into many tropical countries around the globe including Vanuatu, Samoa, Tahiti, Fiji, Sri Lanka, Malaysia, Solomon Islands, and tropical north Australia (Karan, 1975;Black, 1984). This species was introduced into the Cairns region of Queensland in Australia in the 1970s and it is reported that after a relatively short lag time of 23 years its population exploded (Osunkoya et al, 2021;Shi et al, 2021). Navua sedge is now a major biotic constraint to economic production in various agricultural systems in tropical north Queensland, Australia, including the dairy and beef industries and cropping systems such as banana (Musa acuminata Colla), sugarcane (Saccharum officinarum L.) and sweet potato (Ipomoea batatas L.) (Chadha et al, 2021).…”

“…Navua sedge is now a major biotic constraint to economic production in various agricultural systems in tropical north Queensland, Australia, including the dairy and beef industries and cropping systems such as banana (Musa acuminata Colla), sugarcane (Saccharum officinarum L.) and sweet potato (Ipomoea batatas L.) (Chadha et al, 2021). Crop and pasture production have been impacted by Navua sedge and it is also directly causing reductions in dairy and beef production in affected regions (Shi et al, 2021). Over 500 beef producers, dairy farmers and hay producers in the Atherton Tableland region in Queensland are affected by Navua sedge.…”

“…A promising tactic of Navua sedge management will be to deplete the soil seed bank, and for such a tactic, a sound understanding of the species' seed bank dynamics is required. Given the importance of this topic and the understanding that Navua sedge is currently recognised as an increasingly problematic species, particularly in the agricultural areas of tropical north Queensland Shi et al, 2021), the objectives of this study were to:…”

Efficacy of halosulfuron-methyl in the management of Navua sedge (Cyperus aromaticus): differential responses of plants with and without established rhizomes

“…Navua sedge is an extremely aggressive and persistent weed that competes with pastures and crops for light, water, nutrients, and space and has the ability to quickly smother pastures (Vitelli et al 2010). Across tropical north Queensland, the dairy and livestock, sugarcane, and banana industries have raised concerns about productivity losses caused by Navua sedge (Shi et al 2021).…”