The "sterile insect technique" is being used against the codling moth in Hawke's Bay. Photo / Simon Winkley & Ken Walker, Museum Victoria/CC
The "sterile insect technique" is being used against the codling moth in Hawke's Bay. Photo / Simon Winkley & Ken Walker, Museum Victoria/CC
New Zealand scientists have found a new hope against a tide of invasive pests threatening to invade our borders, with hundreds of millions of dollars at stake.
Bioprotection scientists have begun a trial targeting some of our most feared threats, including the brown marmorated stink bug, the Korean pumpkin fly, the European grapevine moth and spotted wing drosophila, a fruit fly.
If they became established, the species could wreak havoc in orchards and vineyards.
Plant and Food Research's bioprotection team was looking to target the potential invaders with a chemical-free approach called the "sterile insect technique".
Large numbers of sterile or partially sterile insects are released into the environment, where they compete with wild males to mate with wild females, reducing the number of successful matings and offspring.
It was already being used in one promising Hawke's Bay trial, in which hundreds of thousands of sterile male Canadian moths were being dropped by drone to combat codling moths that attacked apple, pears and walnuts.
Overseas, the tactic had proven effective against mosquitoes spreading the Zika virus in Brazil, and helped eradicate the pink bollworm moth in California.
The Crown research institute was boosting its bioprotection efforts, at a time when New Zealand was under unprecedented threat from foreign pests.
As world trade and travel increased, so to did the risk, senior plant pathologist Dr Nick Waipara said.
Ministry for Primary Industries figures showed that between 2003 and 2014 air passenger numbers increased 47 per cent, sea containers 37 per cent and parcels 216 per cent.
"Like many of our traditional trading partners we are also trading with new markets and that means we are being exposed to new pests from both new and traditional trading partners."
Professor Max Suckling, who heads the bioprotection team, said the global eradication and response database, Gerda, showed the rate at which pest insects were "going global" was accelerating.
New Zealand, meanwhile, was experiencing a third wave of migration.
"First there was the original flora and fauna, then people arrived with the animals and plants they wanted to grow, and now we seem to be getting fast-moving super pests," Suckling said.
The spotted wing drosophila, a type of fruit fly. Photo / Shane F. McEvey, Australian Museum/CC
The multi-agency effort to eradicate the painted apple moth cost $65 million.
Estimates of the cost to the economy if that moth established here ranged up to $290m, while the cost saved by interceptions, and eradication programmes to date, ranged from $100m to as much as $1b.
Suckling said new technology was also likely to make detection and tracking more efficient.
New super-sensitive electronic sniffers, capable of detecting airborne compounds well below one part per billion, would help detect pests at the border.
Similar electronic sensors could be deployed with pheromone traps tailored to target species to provide live monitoring and reporting, when necessary.
"If a new pest arrives we could deploy prototype traps and link them up to quickly build a picture of spread and density in different areas," Suckling said.
"And we could push texts to people entering those areas, alerting them to the things they need to know, such as not taking plant material out of the zone."
Traps baited with artificial pheromones helped eradicate the European grapevine moth around Napa, California – a pest which spread across 2800 square kilometres in Chile costing its table grape industry NZ$70m a year.
Pheromone traps were also in regular heavy use in New Zealand orchards at this time of year – not as part of an eradication programme but as a management tool.
Orchards are much more lively with insect activity today than in the days of regular and heavy spray use.
The brown marmorated stink bug. Photo / Hectonichus/CC
Orchardists and farmers monitor pest numbers and spray only when they cross a certain threshold.
This formed the cornerstone of the integrated pest management system (IPM) that Plant and Food Research designed together with growers.
Today, there were now virtually no chemical residues on our export apples, meaning they could be exported to more than 70 countries - more than any other apple exporting nation.
A Plant and Food Research study had also shown that mature IPM orchards had the same level of biodiversity as totally organic orchards – just far fewer pests.
A new generation of insect lures was also showing promise.
When insects ate foliage, volatile chemicals were released from the plant that attracted more insects to the feast.
Suckling said lures based on those chemicals would be simpler and cheaper to prepare.
They also attracted broad classes of pest insects – and their predators – not just individual species.
They could be combined with pheromones to attract specific species, as work in that field continues to advance.
"There is no doubt that more insect pests will arrive here," Suckling said.
"Increasing contact with the rest of the world means we are engaged in a never-ending battle to protect our horticulture and native ecology against new threats.
"We have had good success against some of these fast-moving super pests already and now we are developing new tools and international collaborations to take on the next challengers."
