Unwanted or introducedcan have a huge impact on Aotearoa New Zealand’s environment, and native and . Chemicals such as pesticides or poisons can get rid of these species, but are often bad for the environment or affect other species. Alternatives such as trapping, culling or weeding can be time consuming and may only have a tiny impact on the pest population.
A successful Bioforce – breeding bugs for biocontrol.programme reduces or removes the need for other controls.Learn more about biocontrol in
Getting rid of weeds
In Aotearoa, biocontrol agents have been used to control the spread of weeds. For example, six different biocontrol agents currently control the spread of gorse – a prickly and invasive weed introduced from Scotland. The small red spider mite has been the most successful of these biocontrol agents as it can eat enough gorse to reduce the plants’ growth and spread.
Protecting pasture from pests
Biocontrol can also be used to control insect pests that destroy farmland. The clover root weevil is a pest that was accidentally introduced to New Zealand in the late 1990s and has degraded pasture, especially in the Waikato, where it thrived. The introduction of a tiny wasp from Ireland is now helping to control clover root weevil numbers. Find out more about in this article, Irish wasp to the rescue.
Ryegrass is an important food for grazing stock in New Zealand. A type of Amazing ryegrass., called an , is being used to protect ryegrass from attack by insect pests, like the Argentine stem weevil and black beetle. Find out more about in this article,
In 2006 the green thistle beetle, Casida rubiginosa, was selected by Landcare Research Manaaki Whenua after it was found to be the most effective insect in reducing the spread of the Californian thistle – a weed species that costs farmers millions each year in lost production. It was first released in a controlled test in 2007, then released to other areas in Aotearoa. It has been monitored since then, proving to be moderately successful.
The possum problem
The possum is one of New Zealand’s worst pests. Possums have aeffect on the environment – eating native forests, spreading disease and preying upon native birds. At present, possum numbers are controlled with a combination of poison (1080) and trapping. Scientists are currently researching effective and humane alternatives for controlling possum numbers.
One biocontrol strategy being investigated is the development of immunocontraceptives that use baits,, viruses, or parasitic worms. These immunocontraceptives prevent the possums from producing offspring by making them .
This article outlines some initiatives working to achieve New Zealand Government’s vision of becoming predator-free by 2050.
Biocontrol was a potential answer to the controversy surrounding 1080. Read about 1080 in this introductory article.
In our Biocontrol in action unit plan, students carry out a practical investigation to help AgResearch scientists monitor the spread of a tiny wasp and its success as a biocontrol agent for clover root weevil. This can be adapted for other biocontrol agents.
The Pest detective is an online guide to help identify the signs left by pest animals. Developed by the National Pest Control Agencies (NPCA) in partnership with the Ministry for Primary Industries, TbFree New Zealand, the Department of Conservation, and Local Government New Zealand, with substantial sponsorship.
The Biological control agents section on the Environmental Protection Authority (EPA) website explains what biological control agents are, how they work, and the EPA's role in ensuring they are safe for Aotearoa New Zealand.