Urban surveillance key to tackling insect invaders

Urban surveillance key to tackling insect invaders

The discovery of five previously undetected insect species in urban areas has prompted a recommendation to increase surveillance efforts for invasive invertebrates.

Tiny insect invaders can be a major threat to New Zealand’s environment, and the volume of our international trade and travel means our borders cannot be made totally secure. Surveillance is usually targeted at specific pests such as the Asian gypsy moth. However, there is no generalised surveillance in urban areas that may harbour “sleepers” – species that have established but are not yet widespread.

Landcare Research scientist Richard Toft is researching the prevalence of introduced insects in urban habitats, and whether any have established here undetected. At the same time he has been trialling a range of traps, from sticky traps to tent-like “malaise” traps, to see which are most efficient and cost-effective for sampling invasive invertebrates.

Mr Toft and his team trialled traps at the Port of Nelson, and around The Warehouse distribution centre at Wiri in Auckland. He also coordinated malaise trap surveys in suburban gardens in Christchurch, Nelson and Wellington.

Two new introduced beetle species were discovered at Wiri, and are in the process of being identified. Three new introduced species of fungus gnats (small flies) were recorded in suburban gardens. One was very abundant, and is now believed to have been here for more than 20 years. It is not yet known what effect these gnats may have on native ecosystems.

In some typical backyard gardens, half of the moths and 80% of beetles found were introduced species.

At the Port of Nelson, a new ant incursion (an Australian ant, Mayriella sp.) was detected, reported to the Ministry of Agriculture and Forestry (MAF), and subsequently eradicated. Invaders were also discovered in new places; for example, various ant species were recorded for the first time in Nelson or the South Island.

Mr Toft says the research shows the potential benefit of generalised urban invertebrate surveys.

“It is clear that we need to be better aware of what insects are getting here. By way of further illustration, since MAF began surveillance around ports for red imported fire ants in 2002 they have discovered two new introduced ant species established here and have launched incursion responses against six others, as well as detecting an incursion of red imported fire ant at Napier.

“New Zealand has some of the strictest biosecurity measures in the world, but unless we search every square centimetre of every container, detecting all invaders at the border is simply not possible. We need better post-border surveillance, to detect any invaders that have made it past the border, most likely into surrounding suburban areas.

“As suburban areas are usually highly modified and have many introduced plants, they are ideal reservoirs for introduced species, both known and unknown. If we can detect invertebrate pests in their ‘lag’ stage, we can still eradicate them before they threaten our native ecosystems.”

Mr Toft says catching pests at this stage is usually far more cost-effective than battling pests that are well established. “For example, the current effort to eradicate fire ants around Brisbane is costing tens of millions of dollars per annum.” Additionally, having a better knowledge of the variety of invertebrate invaders we have reduces the risk of unwittingly spreading these pests to other countries.

Plans for future research include further identification work on the insect specimens collected during the surveys and continued development of potential surveillance techniques. There will also be work on some of the existing urban “sleepers” to better determine their potential threat to the environment.

Mr Toft says the public can play a vital role in biosecurity by keeping an eye out for the unfamiliar.

“The public are actually very good at detecting larger invertebrate pests and the small ones that make a big nuisance. The painted apple moth, the tussock moth, the Australian saltmarsh mosquito, and the fire ant colony at Auckland were all first detected here by members of the public.”

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