1 Jun 2023

Battling weeds with biocontrol

From Our Changing World, 5:00 am on 1 June 2023

Aotearoa is in the weeds.

There are around 2300 species of native New Zealand plants, but an estimated 25000–30000 species of plants from overseas.

And many of them have gone rogue.

A close up of a creeper plant sprouting from a plastic pot, with brown spots of damage visible on the leaves.

Leaf mining fly attack on old man's beard. Photo: Claire Concannon / RNZ

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Without their natural predators, which co-evolved with them to keep them in check, some of these plants have escaped out of our houses and gardens.

The worst of weeds grow rapidly, spread voraciously and smother and kill native plants. Traditional chemical or mechanical control methods – spraying herbicides or pulling out the weeds – are expensive, time consuming and short-lived. So, what else have we got in the toolbox?

One option is biological control, or biocontrol for short. This involves finding a natural enemy of the weed from its host country to keep it in check. Some insects, mites and plant pathogens have evolved to be extremely plant specific, and these are the agents that Dr Angela Bownes is keen to recruit.

Angela is a senior researcher in weed biocontrol at Manaaki Whenua – Landcare Research. Based on their research campus in Lincoln, she works closely with fellow senior research Dr Ronny Groenteman to investigate different agents that might be helpful in the battle against weeds.

The research they do is to aid the National Biocontrol Collective – a consortium of regional councils, unitary authorities, and the Department of Conservation. The National Biocontrol Collective funds the applied weed biocontrol research that takes place at Manaaki Whenua and has worked with them to develop a weed prioritisation tool to build a hit list of the top weeds to target.

A man in a t-shirt wearing glasses stands in a yellow-lit lab holding a petri dish.

Arnaud Cartier, facilities manager at the Manaaki Whenua Invertebrate Contaiment Facility, and the old man's beard sawfly. Photo: Claire Concannon / RNZ

At the Lincoln campus the researchers work in the specially designed invertebrate containment facility to put the biocontrol agents through their paces. Arnaud Cartier manages the facility, ensuring all the restrictions are in place so that no agent escapes before it is approved for release.

Listen to the episode in which Claire Concannon visits the facility to learn more about biocontrol agents, how researchers ensure they are safe to release, and the hurdles an agent must clear before approval

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