Advice on biological control agents in Mount Aspiring National Park

To: Hon Tama Potaka, Minister of Conservation 
Date: 27 June 2024

The NZCA has recently received an application from the Department, on behalf of Paul
Stephenson, seeking authorisation to introduce two biological control agents into the Young,
Siberia, and Wilkin Valleys of Mount Aspiring National Park, to protect biodiversity values. The
agents are the ragwort plume moth (Platyptilia isodactyla) and ragwort flea beetle (Longitarsus
jacobaea) to control the invasive weed species ragwort (Jacobaea vulgaris).

Release of a biocontrol agent into a national park requires the approval of the Minister who,
in making his decision, shall consult with the NZCA (sections 5A(1) and (2) of the National
Parks Act 1980 refer).

We were advised that ragwort is becoming an ecological issue especially within the Young,
Siberia, and Wilkin Valleys in the Park. Ragwort prefers areas of open space and has been
shown to invade open forests, riverbeds, swamps, pastures and coastal areas and tolerates
a wide range of environmental conditions, except for shade. It is damaging ecologically as it
outcompetes native flora.

Ragwort has proven to be difficult to control by conventional methods of hand pulling and
weed spraying manual controls. Use of biocontrol agents is therefore considered to be a more
cost-effective method in reducing and controlling the population of ragwort. The caterpillars of
the plume moth and the larvae of the flea beetle are the damaging stages that can severely
harm the crown and roots of ragwort plants. It is considered that as few as 2–3 larvae can kill
a plant or alternatively if plants are not killed, then they produce fewer flowers and seeds.

The release of these biocontrol agents was approved by the Environmental Risk Management
Authority (ERMA) in 2005 and they have been widely released across the country on non-conservation land. The Authority also noted:

• The information from Manaaki Whenua is clear and supportive of their use.
• There has been consultation with iwi and Section 4 requirements have been met -
  noting the condition of approval "that tangata whenua are notified beforehand of the
  proposed release of the biocontrol agent and invited to participate".
• The application needs to be "consistent with the Act, the General Policy, and the
  relevant national park management plan [Mount Aspiring]", and they are convinced
  that these have been met.

Therefore, the NZCA, having considered the information before it and, based on that,
recommends to you that authorisation be granted under section 5A(1) of the National Parks
Act 1980 for the introduction of the two biological control agents into the Young, Siberia, and
Wilkin Valleys of Mount Aspiring National Park, for biocontrol purposes to protect the
biodiversity values of the Park.