New Zealand might be an island nation, but that doesn’t stop us from having to deal with a variety of unwanted organisms that find their way to our shores. These pests range from insects like the clover root weevil and varroa mite to Asian date mussels and the fungi Austropuccinia psidii that causes myrtle rust. These invaders threaten our native biodiversity, the quality of our waterways and natural environment and our primary industries such as horticulture.
Scientists are constantly working on ways to stop these pests or to reduce the destructive effect of them. Biocontrol – the use of biological agents – is one method that scientists use to control these pests. For example, an Irish parasitoid wasp has been important in controlling the clover root weevil on dairy farms, and a fungal endophyte has been added to ryegrass to make it resistant to the Argentine stem weevil.
Biocontrol is particularly important in the primary industries – those industries where food is being grown or produced (such as dairy farming, orchards and market gardens). Consumers are becoming more demanding that their food comes from environmentally friendly and sustainable farming methods. Biocontrol leaves no chemical residues, and pests cannot build up immunity to biocontrol agents as they can with chemical pesticides. As well, end products have no chemical residue and they’re safer for people to work with.
So where do farmers and orchardists go when they’re wanting biocontrol agents? Where do the good bugs come from?
Director John Thompson set up Bioforce over 20 years ago. At the time, he was a chemist working in horticultural science and could see the need for a supplier of biocontrol agents. The New Zealand-based company is growing around 10 different bugs for biological control and importing others for supply. It also sources and on-sells beneficial microbes for fungal control.
Bioforce supplies biocontrol agents for the horticulture industry. Learn about some of its methods for rearing beneficial bugs.
Bioforce supplements its locally grown bugs with some imported varieties. It imports nematodes such as Steinernema carpocapsae to control beetles, cutworms and other moths in soil and turf. Nematode production is an expensive microbiology process where nematodes are grown in fermentation tanks, and it has been more efficient for Bioforce to import and distribute from offshore companies.
Bioforce predominantly supplies market gardeners – especially those growing tomatoes, capsicums, cucumbers and strawberries in glasshouses. The team at Bioforce works with many of the growers, helping them to set up and tailor an integrated pest management (IPM) programme for their individual operations. IPM programmes are an environmentally sensitive approach to the management of pest organisms and involve pest identification, pest monitoring, integration of different pest control methods and, importantly, the setting of pest threshold levels that act as a trigger for the introduction of control methods.
Understanding pests and pest thresholds is important because biological controls do not completely eradicate pests – they maintain pest populations at levels low enough that any damage caused is insufficient to warrant chemical intervention. Effective biological control requires the use of beneficial organisms that are able to reach an ecological balance with the pest population at levels that don’t financially impact growers.
What does Bioforce grow?
Bioforce grows a variety of invertebrate predators and parasitoids. A parasitoid is an organism that has young that develop on or within another organism (the host), eventually killing it. One of these parasitoid invertebrates produced by Bioforce is the wasp Aphidius colemani. It is used to control a variety of aphids and Encarsia formosa (tradename Enforce™), which specialises in parasitising greenhouse whitefly.
It also grows a number of straightforward predators on site like pirate bugs (Orius vicinus) and dusty ladybirds (Scymnus loewii). Ladybirds are generalists – they are primarily an aphid predator, but they will also predate on psyllid and whitefly eggs, mites and the eggs of larger insects such as butterflies and moths.
So how do you grow and harvest bugs for on-selling?
Growing and harvesting biocontrol bugs
Growing beneficial bugs is not as straightforward as you might think! The production of E. formosa parasitoid wasps starts by growing a host plant – Bioforce grows tobacco plants as host plants in glasshouses. The whitefly pest species is then introduced to the host plants. Once the pest species is established, the E. formosa wasp species can be introduced. The whitefly has four larval stages, and E. formosa lays its egg in the final larval stages of the whitefly’s life cycle. The parasitised larvae turn black about halfway through their growth cycle and can then be harvested from the underneath side of the tobacco leaves. The E. formosa nymphs have about 2 weeks before they hatch from the host larval shell to become a biocontrol in the field or glasshouse. The females can lay up to 50 eggs in their life, one egg per whitefly larvae.
Bioforce markets Encarsia formosa wasps as Enforce™. The E. formosa nymphs are packaged in cardboard tags that growers hang from plants.
Harvesting and packaging of the beneficial bugs depends on the bug. E. formosa nymphs are washed from the tobacco leaves and dried, the nymphs are packaged in cardboard tags and the tags are hung at intervals on the crop they are to protect. Ladybirds are delivered as eggs embedded in fabric on tags. A. colemani larvae are delivered within mummified aphids. Mites are delivered in a dry mixture of the mineral vermiculite with a supply of their food.
Research, development and regulations
Bioforce runs ongoing research and development aimed at improving production of the species being reared. It also assists in field trials to look at the efficacy of biocontrols.
Due to a stringent regulatory framework for the introduction of new organisms into New Zealand, Bioforce does not research organisms as possible biocontrols but waits until organisms are approved before it considers importing or growing a new species.
In New Zealand, regulations relating to new organisms are outlined in the Hazardous Substances and New Organisms (HSNO) Act 1996. The Environmental Protection Agency (EPA) is the organisation responsible for assessing new organisms for release, and the Ministry for Primary Industries enforces and monitors the use of new organisms and biocontrols. The regulatory framework is important to assure new organisms entering New Zealand do not cause unwanted problems – for example, scientists have to make sure that any new organism does not pose a threat to native species.
Nature of science
Without context, the word ‘bug’ can mean anything from an insect to a nematode to a computer glitch. For this reason, most scientific texts use technical words with precise meanings. With informal or popular texts, the need for precision is not as significant. Learning the language of science supports the ‘Communicating in science’ strand of the New Zealand Curriculum.
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.
For general information on biological controls, read Biocontrol.
Biological control has the potential to provide novel ways to control possums – read more in Biological control of possums.
A little mite like a tiny spider the size of a pinhead has been plaguing New Zealand’s bee industry. But help for the bees might be at hand. Scientists have been investigating a fungus biocontrol that may well turn out to be the mite’s worst enemy. Learn more in Fighting a little bee mite.
You can learn more about integrated pest management programmes and view different biocontrol products on the Bioforce website.
See on the Manaaki Whenua – Landcare Research website their section on weed biocontrol education resources.
To understand the regulations involved in bringing new organisms into New Zealand for biocontrol, go to the Environmental Protection Agency website or Biocontrol information resource for EPA applicants. To learn about some of the biocontrol agents already brought into New Zealand, go to BCANZ biocontrol agents introduced to New Zealand.
The Science Learning Hub thanks Showdown Productions for its assistance in the writing of this story.
The video clip is courtesy of Rural Delivery a television programme that looks at excellence and innovation within the primary industries in New Zealand.