'Trojan' technique could help make NZ pest-free

"The essence of our idea is to use these mitochondrial mutations to produce continuous, self-sustaining biological control," Otago University researcher Professor Neil Gemmell says. Photo / File

A world-first technique just proven by Kiwi scientists on fruit flies could one day help eradicate pests like mice and wasps.

The "Trojan Female Technique" (TFT) - in which females pass on genes that make male offspring infertile - offers pest-control advantages that are likely to help as New Zealand works toward its 2050 predator-free goal.

"This is a world-first proof-of-concept and we need to test the general applicability of this approach more widely," said Professor Neil Gemmell of the University of Otago's Department of Anatomy.

Gemmell said the approach used naturally occurring mutations in mitochondrial DNA that affected male, but not female, fertility and fitness.

Mitochondria were considered the "power generators" of a cell and turn oxygen and nutrients into chemical energy which runs the cell's metabolic activities.

"The essence of our idea is to use these mitochondrial mutations to produce continuous, self-sustaining biological control.

"What we discovered some years back is that, as a by-product of the maternal inheritance of mitochondrial DNA, mutations that affect only males can occur quite commonly in populations, potentially contributing to fertility issues in some populations.

"Our idea turns this problem around. If these mutations can affect population viability, we wondered if they might be turned into a tool that has the potential to control and even eradicate pests."

Gemmell said the paper - recently published by eLife and conducted in collaboration with Dr Damian Dowling and Dr Jonci Wolff of Monash University - showed population reduction could be achieved in lab-raised fruit flies.

Broadening this technique to introduce Trojan females into wasp and pasture weevil populations was under way, with funding from the Biological Heritage National Science Challenge and the Ministry of Business, Innovation and Employment.

"There are several advantages of this approach, which does not require elaborate, and probably uncontrollable, delivery systems, such as parasitic vectors and intermediate hosts.

"It is species specific, there is little danger of accidental release or cross-species transmission, and it is adaptable to any pest species, because mitochondria are common to all higher organisms.

"While there are many tools to control pest populations, we think this might be an important part of a growing arsenal. Certainly around New Zealand there is a great deal of interest in this approach as a way to control rats, possums and stoats as part of the Predator Free 2050 goal."

Co-author Dr Dan Tompkins, of Landcare Research, said another critical advantage was that it did not require genetic modification.

"This technique is currently being explored for application to pasture weevils, which cause millions of dollars of loss to the dairy and other livestock industries each year.

"This is particularly relevant at the moment, given data suggesting that the current biocontrol of these weevils could be failing.

"It could potentially also be used for controlling vertebrate pests, but that line of research is several years behind insect work and is currently unfunded in New Zealand."

Pests are estimated to cost New Zealand about $3.3 billion a year through lost productivity and cause profound damage to native fauna and flora.

The implications globally are even larger, particularly when insect-borne diseases, like malaria, are considered.

Entrepreneur to head predator-free effort

Meanwhile, the entity that's set to lead New Zealand's Predator Free 2050 goal is to be headed by entrepreneur Ed Chignell.

Chignell founded Treescape New Zealand, a Trans-Tasman company specialising in tree, vegetation and environmental management, and has spent 37 years with as co-CEO.

He has now been appointed as chief executive of Predator Free 2050 Ltd, which is responsible for managing and leveraging $6 million a year of the Crown's investment into ridding New Zealand of possums, rats and stoats by 2050.

"I'll be looking to bring the required skills of collaboration, coordination and development to take Predator Free 2050 Ltd towards the goal of eliminating all possums, rats and stoats in our country," he said.

His focus in the first six months is to meet with all players currently doing work and research in this field, while also meeting with philanthropic companies."

An estimated 25 million eggs or chicks of native birds are killed by introduced predators every year. That's a huge number and it is the path to extinction for many of our endemic bird species.

"In turn, those species are indicative of New Zealand's total biodiversity; if they are under threat, it means all our fauna and flora is under threat. This makes the task ahead a crucial one for all New Zealanders."

Board chair Jane Taylor said the entity now had a draft science strategy to develop breakthrough technology, which would be made public later this year.

"We're also developing a strategy for managing additional Crown funding for large-scale collaborative predator control projects and expect to announce our plans for identifying, selecting and funding suitable projects as the year progresses."