Advice on proposed biological control agents into Kaniwhaniwha Stream Recreation Reserve, to protect biodiversity values
28 April 2023: Read NZCA's advice to the Minister of Conservation on the proposed introduction of biological control agents into Kaniwhaniwha Stream Recreation Reserve, to protect biodiversity values.

To: Hon Willow-Jean Prime, Minister of Conservation 
Date: 28 April 2023

The NZCA has recently received an application from the Department, on behalf of Nadene Berry, of Te Pahu Landcare group, seeking authorisation to introduce four biological control agents into Kaniwhaniwha Stream Recreation Reserve, Waikato, to protect biodiversity values. The agents are Tradescantia leaf beetle (Neolema oglobini), Tradescantia tip beetle (N. abbreviata), Tradescantia stem beetle (N. basicostata), and yellow leaf spot fungus (Kordyana brasiliensis) to control the invasive weed species Tradescantia (Tradescantia fluminensis).

Release of a biocontrol agent into a Crown reserve requires the approval of the Minister who, in making her decision, shall consult with the NZCA (s51A Reserves Act 1977 refers).

We were advised that Tradescantia is regarded as a serious plant pest, that has high shade tolerance, spreads easily through stem pieces, and forms dense mats under forest canopy and along stream banks suppressing native flora from growing. Tradescantia is a very persistent weed that is difficult to control with current herbicide methods alone.

The release of these biocontrol agents was approved by the Environmental Risk Management Authority (ERMA) in 2011 and they have been widely released across the country on non- conservation land. The biocontrol committee also noted:

  • The information from Manaaki Whenua is clear and supportive of their
  • 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 Conservation Management Strategy [Waikato]", and they are convinced that these have been met.

Therefore, the NZCA’s Biocontrol Committee, acting under delegation from the full Authority, has considered the information before it and, based on that, recommends to you that authorisation be granted under section 51A of the Reserves Act 1977 for the introduction of the four biological control agents into Kaniwhaniwha Stream Recreation Reserve, Waikato, for biocontrol purposes to protect the biodiversity values of the reserve.