Boneseed

(Chrysanthemoides monilifera)

Progressive Control Pest

Boneseed is a perennial shrub growing to 3 metres. Stems are woody, with many branches. Leaves are bright to dark green, with a mealy/powdery surface, alternate, toothed and hairless. The flowers are bright yellow and daisy-like, with 8-12 petals clustered at the ends of the branches. Boneseed flowers in September to February. It produces black berries that are spread by birds but can also be water-distributed.

Reasons for the Strategy

Green steemed boneseed shrub with bright yellow flowers.

Boneseed is an aggressive coloniser and competes with native species, especially in coastal areas. It is considered a serious environmental weed in other parts of New Zealand, such as Canterbury and Manawatu. It has the potential to displace native species in the Tasman-Nelson region on coastal cliffs, sand dunes, and in salt marshes.

Boneseed is assessed at “3” on the infestation curve. It is widespread in the Port Hills of Nelson. However, outside this area, known sites include Cable Bay, Kina, Collingwood and Jackett Island. This control programme focuses on the infestations that pose the greatest risk to the coastal environment and those that could increase its spread. The widespread distribution, number of property owners involved, and the difficult terrain of the Port Hills make the provision of advice, monitoring, and investment in biological control (biocontrol) the most cost-effective measures to contain the infestation in this area. A biocontrol agent (a defoliating caterpillar) has become available and it will be trialled during the term of this Strategy. Outside the Port Hills, the low incidence of Boneseed in the Tasman-Nelson region, extensive areas of suitable habitat, and the potential for it to cause significant adverse effects, mean the benefits of progressive control far outweigh the costs.

Objective

  1. To reduce the density and distribution of Boneseed outside of the Port Hills as defined on the map below by ensuring that all known sites in the Tasman-Nelson region are inspected annually and all live plants are destroyed during the term of the Strategy.
  2. To introduce a biocontrol agent into the Port Hills during the term of the Strategy and monitor its effectiveness in reducing Boneseed’s distribution and density.

Alternative Measures

The alternative option of “do nothing” or relying on voluntary control will not achieve the objective of eradication, and will result in significant additional costs to the community with respect to lost natural values and the increased cost of control in the future. Requiring total control of Boneseed is not practical given its widespread distribution in the Port Hills area, and the difficulty of eradicating it from areas where it is providing a soil stabilisation function.

Strategy Rule for Boneseed

The occupier shall destroy all adult and juvenile forms of Boneseed on land that they occupy except within the Boneseed Containment Area as defined on the map below. A breach of Strategy Rule 5.1.5 is an offence under Section 154(r) of the Biosecurity Act 1993.

Biosecurity Act Requirement

No person shall knowingly sell, propagate, breed, release, or commercially display Boneseed, under Sections 52 and 53 of the Act.

Map showing Port Hills Boneseed Containment Area

Map showing Port Hills Boneseed containment area.