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Finding biocontrol agents

Step one: Finding biocontrol agents

Before we can find an effective biocontrol agent, we need to understand the weed. We need to learn:

  • where and why the weed is a problem in New Zealand
  • where the weed originally came from (this helps us locate natural enemies specially adapted to the weed)
  • whether the weed is one species or variety, or is a combination of species or varieties (some natural enemies may only attack a particular variety of a weed)
  • whether the weed has any enemies in New Zealand (if we know what’s here already, we can look for a new enemy that attacks a different part of the plant and avoid agents that might be killed by predators or parasites).

Step two: Look for the weed’s natural enemies overseas

We find these enemies by:

  • reading scientific journals and books about the weed
  • talking to scientists overseas who may have experience with the weed
  • going to the weed’s country of origin and collecting insects and diseases growing on it

We try to find as many natural enemies as we can. We look for organisms that attack different parts of the plant (roots, leaves, seeds, etc.) and at different times of the plant’s life cycle/seasons. We pay particular attention to enemies that cause significant damage to the weed in its native habitat. This gives us a wide range of possibilities. We need all the possibilities we can get, because many natural enemies won’t make it past step three!

Step three: Test for safety

It is important to check that any potential biocontrol agents won’t themselves become pests. To do this we carry out safety testing to make sure they will not attack important plants in New Zealand—native plants, crops, or other economically important plants. We often do this testing overseas. However, sometime it is more practical to test potential agents in New Zealand inside a secure containment facility.

To be accepted as a possible biocontrol agent, natural enemies have to be very picky eaters! Natural enemies that attack desirable plants are rejected. Many enemies don’t pass this step.

Step four: Import into New Zealand

Landcare Research has a permit from the EPA (Environmental Protection Agency) to import potential biocontrol agents into containment for further study.

In containment we can:

  • Check that the right insect or plant disease has been imported and is not contaminated with other species (some look alike, and we need experts to confirm their identity).
  • Test the agent for parasites and diseases (we want to import our biocontrol agent and no other organisms with it). Agents carrying parasites or diseases must be treated until they are clean. Sometimes that is too difficult and it is necessary to start again with a new shipment.
  • Complete any unfinished host-testing (e.g. native plants not available overseas). Reject the agent if it will cause unacceptable damage.
  • Synchronise the agent’s life cycle to New Zealand seasons (this is particularly important for agents from the northern hemisphere).

Step five: Apply for permission to release the agent

If the biocontrol agent has passed all the tests described above, we ask permission to release it into the environment. The application process is long and rigorous.

  • We prepare an application summarising the case to release the new agent. The application includes detailed information about the agent, the weed problem we hope the agent will address, and all known risks, costs and benefits. We consult with key stakeholders to ensure their views are included.
  • We send our completed application to the EPA.
  • EPA asks for public comment on the application.
  • EPA reviews the application, public response, and expert advice. They weigh the risks and benefits and decide whether to release the agent, ask for more information, or prohibit release of the agent. Sometimes a public hearing is held so any issues can be publicly debated.

Step six: Release the biocontrol agent

If the EPA approves release of the biocontrol agent in principle, we then apply to the Ministry for Primary Industry for permission to take it out of containment. They check that the agent has been correctly identified and is clean. Once out of containment, the agent is reared in large numbers. When we have plenty of material the agent is released at suitable weedy sites. The agents are then generally left undisturbed for a year.

Step seven: Monitor the agent

After a year, biocontrol agents are checked to see if they survived. Agents may need to be released several times before they become established. Once agents are doing well at one site, some are collected and released at new sites to help speed up their spread.

Follow up studies help us learn how much impact an agent is having on the weeds. We use this information to decide whether we need to import more biocontrol agents or do other things to help the agent be more effective.