New research showing how efforts to keep pests out of countries are failing to keep up with the pace of globalisation means New Zealand must be more vigilant than ever, a biosecurity expert says.

A just-published study shows the number of invasive species worldwide has been increasing in the past 200 years, with no sign of slowing down.

On a global scale, this meant there were almost two new pest incursions somewhere in the world every day.

New Zealand needed to ensure biosecurity was right at the top of the business and tourism agenda, said the study's senior author, Professor Philip Hulme, of the Bio-Protection Centre at Lincoln University.

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"As a country with a unique flora and fauna as well as strong economic dependence of agriculture, it is vital for New Zealand to have stringent and robust biosecurity policies," Hulme said.

"I'm not sure this message gets through enough to our millions of tourists, the airlines, or importers."

The study, involving an international team of 45 scientists, found increases in invasive species were associated with human activities, particularly the expansion of agriculture, horticulture and global trade.

While new species can boost diversity in an area, it could also have detrimental affects on the native ecosystem, economy, environment and human health.

In some cases, it could bring about the extinction of native species.

But there were some positives.

New Zealand was one of the few countries shown to have fewer records of weed incursions in the past few decades.

"The success at reducing weed incursions is largely down to New Zealand implementing a strict biosecurity policy in 1993. As such, our biosecurity systems can be viewed as a global example of best practice."

Altogether, the researchers compiled more than 45,000 records of about 17,000 species worldwide, including plants, birds, insects, mammals, fishes, fungi, algae and molluscs.

Collecting this long-term data was difficult and numbers were likely to underestimate the full extent of species incursions, Hulme said.

The study's findings highlight the continued need for improvements in national legislation and international agreements to help mitigate invasions and keep up with effects from increasing globalisation.

"New Zealand is already leading the way and hopefully through Biosecurity 2025, New Zealand is on the road to future-proofing the system to meet increasing global trade and travel that present continual new challenge."

Weed-busting bugs get to work

Meanwhile, two insects that will tackle a weed threatening the viability of New Zealand farms have been released into the environment for the first time.

A moth and a beetle, imported from Georgia by Landcare Research in 2014, have tutsan (Hypericum androsaemum) in their sights.

The weed is thriving in parts of the central North Island, where it cost an estimated $400 per hectare per year to control.

The foliage-eating beetle, Chrysolina abchasica. Photo / Supplied
The foliage-eating beetle, Chrysolina abchasica. Photo / Supplied

Landcare Research's Hugh Gourlay said the release of the beetle and moth, at Taumarunui this week, was the culmination of nearly a decade of hard work.

"Tutsan is a threat to farmers' livelihood and because of this they themselves have turned to science for a solution by forming TAG [Tutsan Action Group], a group of farmers who have dipped into their own pockets and joined forces with the likes of us, Landcare Research, Horizons Regional Council and the Sustainable Farming Fund, to come up with a solution."

Gourlay was optimistic the foliage-eating beetle (Chrysolina abchasica) and the fruit, leaf and stem-feeding moth (Lathronympha strigana) would be as effective as other recent success stories, such as the ragwort flea beetle and St John's wort beetle.

The latest two insects were approved for release by the Environmental Protection Authority last May after an application was made by TAG.

The fruit, leaf and stem-feeding moth (Lathronympha strigana). Photo / Supplied
The fruit, leaf and stem-feeding moth (Lathronympha strigana). Photo / Supplied

"A rust [Melampsora hypericorum] was self-introduced into New Zealand several decades ago and controlled tutsan throughout the country, but the weed, for a variety of reasons, has taken off in recent years and we hope that by introducing some help in the form of these two new agents we can get this problem under control again."

Recent research into tutsan populations in New Zealand had shown that the plant here had two distinct genetic types: one that grows in the North Island and another in the South Island.

The North Island plants were not being controlled by the North Island rust anymore, whereas it appeared that the other rust type was keeping the South Island plant populations under control.

Gourlay located both bugs in the former Soviet republic of Georgia in 2014 and brought them back into New Zealand, where he has reared them in Landcare Research's state-of-the-art containment facility in Lincoln, which now hosts an insect population big enough to support releases of the moth and beetle into areas where the weed is flourishing.

Tutsan is thriving in parts of the central North Island, where it costs an estimated $400 per hectare per year to control. Photo / Supplied
Tutsan is thriving in parts of the central North Island, where it costs an estimated $400 per hectare per year to control. Photo / Supplied

Tutsan was found all over New Zealand but was a significant problem in parts of the central North Island, where it formed extensive patches that threaten agricultural, forestry and conservation land.

Unpalatable to stock, hard to kill and shade-tolerant, tutsan was particularly prevalent in areas where the land has been disturbed by the likes of forestry. It was easily spread by birds, mowers, machinery, and soil and water movement.

Common seed sources include roadsides, conservation and wasteland, old gardens and forestry.

Major New Zealand incursions

• Western flower thrips - 1992
• Guava moth - 1997
• Varroa mite - 2000
• Lettuce aphid - 2002
• Iris yellow spot virus - 2006
• Tomato potato psyllid - 2006
• Psa-V - 2010
• Great white cabbage butterfly - 2010
• Hadda beetle - 2010