1 Apr 2018

Hunting exotic disease-carrying mosquitoes

From Sunday Morning, 10:45 am on 1 April 2018

New Zealand could become home to exotic disease-carrying mosquitoes because of climate change and urbanisation.

The discovery of Culex sitiens mosquitoes in the Kaipara Harbour north of Auckland proves non-native mosquito species can sneak in and set up home quite comfortably here, says insect scientist Sophie Hunt.

Mosquito researcher Sophie Hunt

Sophie Hunt Photo: Supplied

At present there are 15 mosquito species in New Zealand – not counting Kaipara Harbour's recent arrivals – 12 of which are found nowhere else in the world.

Currently, none of these carry human disease, but global warming makes it a real possibility other species that do could establish themselves here in the future, Hunt says. 

“With climate change, and the way we’re creating more habitats for them, I think it’s probably a matter of time.”

The warmer it is, the easier it is for the insects to go through their life cycle, she says.

“It’s just faster for them to establish.

“I got a really big shock when I moved from Christchurch to Auckland – how many there are here. It is a big difference.”

Hunt recently co-wrote a paper highlighting the risk as part of a Masters degree at the University of Canterbury.

Her research team surveyed Canterbury and the South Island’s West Coast for two commonly found mosquitoes – the stripy-legged Aedes notoscriptus, from Australia, and the native Culex pervigilans, the type that makes a buzzing sound at night.

The disease-carrying Aedes notoscriptus mosquito is from Australia.

Aedes notoscriptus Photo: Angus McIntosh

“We measured any kind of habitat we could find; forest, natural grassland and farmland and urban areas.

“We just found then so much more in urban areas because there’s so many more habitats.”

In built-up areas and gardens, there are fewer predators than in forests and lakes, she says.

“Dragonflies and damson flies, they all live in the water before they start flying and they really like eating mosquitoes. If you’ve got just a tyre or a pot in the backyard that’s got water in it the mosquitoes can grow up in that because there’s no predators.”

There are various methods of control, including chemical, and Hunt says ports and MPI are doing a great job detecting the insects in ships and vehicles at the border.

The main thing people can do themselves is to try to limit potential habitats, Hunt says.

“[Mosquitoes] don’t fly that far. If you’ve got bucket-loads of mosquitoes flying around you’ve probably got standing water somewhere which is breeding them.”

During the survey, Hunt visited one mosquito-plagued property only to discover a large drum of seaweed soaking in water that a resident was preparing for use on her garden.

“It was full of mosquito larvae – she had just been breeding them herself.”

Hunt's study was co-written with Dr Mark Galatowitsch and Professor Angus McIntosh of UC's School of Biological Sciences and recently published in the ecology journal Freshwater Biology.