Declared Plant Policy under the Natural Resources Management Act 2004
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D  eclared Plant Policy
under the Natural Resources Management Act 2004 polygala (Polygala myrtifolia) Polygala myrtifolia is a South African garden escape, a shrub growing up to 3 metres tall. It has become established in some coastal areas on Eyre Peninsula, Yorke Peninsula, Kangaroo Island, and more generally in the Southern Lofty and South East regions. Management Plan for PolygalaOutcomes
Objectives
Implementation
Regional Implementation Refer to regional management plans for further details.
DeclarationTo implement this policy, polygala is declared under the Natural Resources Management Act, 2004 throughout the whole of the State of South Australia. The movement or transport of the plant on a public road by itself or as a contaminant, its entry to the State, or the sale by itself or as a contaminant is prohibited. NRM authorities may require land owners to control polygala plants growing on their land. NRM authorities are required to control plants on road reserves, and may recover control costs from the adjoining land owners. Polygala is declared in category 2 under the Act for the purpose of setting maximum penalties and for other purposes. Any permit to allow its movement or sale can only be issued by the Chief Officer pursuant to section 188. The following sections of the Act apply to polygala throughout each of the NRM regions noted below:
ReviewThis policy is to be reviewed by 2020, or in the event of a change in one or more regional management plans for polygala. Success will be measured by the number of new infestations recorded. Weed Risk Invasiveness Polygala has high seed production. The seed is dispersed by ants over short distances as it has an oil body attached, as is typical for Polygala species around the world. Wind and water may also carry seeds short distances. It lacks any adaptations for long-range dispersal, which appears to be dependant on human activity through planting and movement of infested soil. Seedlings germinate in autumn and quickly establish before the next dry season. Its high rate of spread is inferred from observations at Discovery Bay, Victoria, where an infestation of P. myrtifolia doubled its area from 500 ha to 1000 ha over 10 years. The infestations on unallotted Crown land near Port Lincoln and in the Bernoulli Conservation Park appear to have spread as rapidly into vegetation with no visible disturbance. Polygala has the potential to spread more widely into some native vegetation types with consequent reduction in some native species. As the main pathway of long-range dispersal is planting in gardens, a prohibition on its sale will minimise further spread. Impacts Polygala myrtifolia establishes under the canopy of native vegetation where it reaches high densities. It is most significant as an invader of coastal dune scrublands, where it can form a monoculture replacing Leucopogon parviflorus and Acacia longifolia subsp. sophorae. It displaces native species due to its dense growth and the heavy layer of leaf litter formed under it. The dense thickets that result restrict access. Potential distribution Most infestations occur on sandy, well-drained soils. Polygala does not appear to tolerate heavy frosts, which may also confine it to near-coastal areas. Feasibility of Containment Control costs No herbicides are registered for use on polygala, but it is covered by permits for the use of glyphosate and metsulfuron-methyl on woody weeds in general. Small plants can be hand-pulled, and larger plants can be cut off at the base. These control methods are labour-intensive. The possibility of biological control of polygala is being investigated by the Victorian government. Persistence The seed is long-lived, forming a seed bank in the soil under infestations. The seed bank enables dense seedling regeneration after a cool burn or clearing. Current distribution Polygala is still scattered in its distribution around the coast, and further dispersal is likely to depend on its deliberate planting. State Level Risk AssessmentAssessment using the Biosecurity SA Weed Risk Management System gave the following comparative weed risk and feasibility of containment scores by land use:
ConsiderationsPolygala was introduced as a garden shrub in the 19th century and was first recorded naturalised in 1926. Most polygala infestations occur in native coastal vegetation on public land. Risk assessment indicates the action of site management in native vegetation, and monitoring in southern permanent pastures. While sale and movement are prohibited uniformly across the State, regional actions vary according to amount of vulnerable native vegetation in each region. The Adelaide Mount Lofty Ranges, Eyre Peninsula and South East regions will manage polygala by site protection; the South East also aims to prevent spread to key sites and assets of high economic, environmental and/or social value. The Alinytjara Wilurara and Northern and Yorke regions will destroy any infestations of polygala as the weed is absent from that region, and Kangaroo Island aims to contain spread. Polygala will be managed in the South Australian Murray Darling Basin region. Only limited action, by prevention of any sale of polygala, is undertaken in the South Australian Arid Lands. The impacts on native vegetation of polygala control by herbicides or mechanical clearance must be considered. Restoration or revegetation of treated sites is necessary to prevent erosion or invasion by other weed species. A garden hybrid, Polygala X dalmaisiana, includes several cultivars. They are all smaller shrubs that have not been found naturalised in SA although they may produce viable seed. This hybrid is not included in the declaration. Synonymy Polygala myrtifolia L., Sp. Pl. 2: 703 (1753) Taxonomic synonyms: Polygala amoena Thunb., Prodr. Fl. Cap. 2: 120 (1800). Polygala myrtifolia var. amoena (Thunb.) Harv., Fl. Cap. 1: 83 (1860). Polygala myrtifolia var. grandiflora Hook., Bot. Mag. 64: t.3616 (1837). The name Polygala grandiflora has also been misapplied to P. myrtifolia. Common names include Bellarine pea, boukappie and septemberbosssie. Reference Adair, R.J., Shackleton. A., Stajsic, V. & Gajaweera, R. (2012) The Biology of Australian Weeds 61. Polygala myrtifolia L. Plant Protection Quarterly 27(4): 119-130.
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