Biological control agents

Biological control agents (or BCAs) are a way of managing pests, such as weeds and insects, safely, sustainably, and cost-effectively.

Biological control (or biocontrol) involves the use of biological control ‘agents’, or BCAs. These agents are introduced into the environment to target a pest species, with the aim of reducing the pest's population or abundance in the environment.

Biological control is increasingly being recognised as an essential component of integrated pest management systems, and contributes significantly to sustainable pest control.

Reducing reliance on chemicals

Weeds are one of the most intractable pest problems in New Zealand and have massive adverse effects on productive land, natural habitats, and taonga species.

Biological controls reduce reliance on conventional pest controls such as herbicides and pesticides, which may be prohibitively expensive to control pests over widespread areas, and which can also result in reduced productivity and biodiversity loss.

Assessing the risks

We have developed world-leading qualitative risk assessments to analyse and weigh up environmental, economic, societal, human health, and cultural values into a decision-making framework for using new biological control agents in New Zealand. 


Insect pest biocontrol agents approved for use in New Zealand


  • A small wasp (Thripobius semiluteus) was approved to control greenhouse thrips in June 2000.

 A wasp (Pseudaphycus maculipennis now known as Acerophagus maculipennis) was approved to control the obscure mealybug, which damages pip fruit crops, in August 2000.


  • An Irish strain of a parasitic wasp (Microctonus aethiopoides) was approved to control the clover root weevil (a significant pest of New Zealand's main pasture species) in November 2005. As this is a release with controls, this wasp strain remains a new organism.

 The wasp parasitoid Cotesia urabae was approved for the control of the gum leaf skeletoniser - a threat to eucalypt trees in July 2010


  • The parasitoid wasp Mastrus ridens was approved to control codling moth (Cydia pomonella) in June 2012.


  • Tamarixia triozae


  • Samurai wasp (Trissolcus japonicus) was conditionally approved to be released in August 2018. This approval can only be used by the approval holder (Brown Marmorated Stink Bug Council).











Weed biological control agents approved for use in New Zealand Plus