Biological control (biocontrol) uses one living organism to control another. It is a way to control weeds and pests by introducing a natural enemy or predator into the environment.

The number of introduced plant species have dramatically increased over the years. Some of these plants are already weeds or becoming weeds. Weeds invade sensitive or native habitats, or productive land. Similarly, many insects hitchhiked to New Zealand with the development of trades, and some species negatively impact the primary industries and the native environment.

Different organisms such as beetles, wasps, mites and fungi can be used as biocontrol agents to stop introduced weeds and insects from damaging natural habitats, taonga species, and farms in an environmentally friendly way.

The underlying principles of biocontrol are safety, self-sustainability, and cost-effectiveness.

Using biocontrol to target weeds and agricultural pests

Biocontrol can be cheap over the long term and is the least damaging way to target weeds and pest insects over a long period of time. They are effective over widespread areas, and in areas that are hard to reach like hilly, bush-covered terrain. However, the action of a biocontrol agent is unlikely to fully eliminate a weed or a pest insect. Normally a combination of control methods is necessary.

Safer for non-target species

Most plants and insects introduced into New Zealand do not have the same natural enemies that they have at home. This means they can flourish here, as there is nothing to naturally keep them under control. Over time they can turn into weeds, pests or predators.

Most organisms considered as potential biocontrol agents are specific to their hosts, making them unlikely to damage non-target plants and animals. In comparison, agrichemicals are generally less specific and can also kill non-target plants and animals.

There is rigorous testing and research

A lot of research goes into testing biocontrol agents before they are released. Safety of the people and the environment is paramount. Research of new biocontrol agents can take 5 to 10 years, and can be costly to undertake.

Researchers usually only consider biocontrol agents that are the natural enemies of target weeds and pests, so it is unlikely the biocontrol agent will attack and harm non-target plants and animals. Researchers assess the risk of damage to non-target plants using procedures endorsed internationally.

Benefits of using biocontrol agents

• While implementing a biocontrol programme can be lengthy and expensive, ongoing costs are minimal.
• Some weeds can’t be fully controlled by traditional methods. They quickly re-sprout after herbicide application or they become resistant to herbicides over time. Biocontrol agents, however, keep coming back as the weed grows.
• Biocontrol agents can penetrate hilly and inaccessible areas easily.
• Biocontrol can be environmentally friendlier than conventional methods.
• Biocontrol agents are safer than agrichemicals for non-target species.

These before and after pictures show how effective biocontrol agents can be. The first set of pictures shows biocontrol success in Tongariro National Park – the weed is heather (Culluna vulgaris) and the agent is the heather beetle (Lochmaea suturalis).

The second set of pictures shows the success story of a fungus (Kordyana brasiliensis) that attacks the weed Tradescantia (Tradescantia fluminensis).

Success story of a fungus that attacks the weed Tradescantia. Image credit: Ben Wolf, Waikato

Our role in biocontrol

Our approval is required to release a new biocontrol agent into the environment. Applicants should make a case to the EPA addressing all the pros and cons.

The investigative process is long and rigorous. We invite the public to participate in this process by making submissions and attending hearings (if a hearing is needed). We also incorporate mātauranga Māori into our decision-making as Māori believe in kaitiakitanga – preserving the environment for future generations.

Our risk assessment weighs up environmental, economic, societal, human health, and cultural values into our decision-making framework.

If we grant approval, biocontrol agents first come into a containment facility where they are bred in a controlled environment.

Our approval is also required to introduce biocontrol agents into a containment facility, or to release them into the environment.

Read about approvals to release biocontrol agents on the Manaaki Whenua Landcare website 

EPA approvals lapse after five years

Any approval to import a plant or animal for release or to release an organism from containment lapses 5 years after the date of the approval, unless the organism is already released into the environment, or an extension of the time limit is granted.

Check with us or the applicant to confirm whether an organism has been released yet before using any of these approvals.