Super pests resist spray

They're the bane of barbecues and a pain at picnics, but flies are no longer content with spoiling summer occasions.

Pest controllers say business is booming as a strain of super-insects makes a mockery of wintry weather, creating unprecedented demand for their services.

Nigel Stevenson of Fumetech Pest Control in Auckland says flies have been more active in generally higher temperatures and are harder to kill.

"As the weather gets warmer the fly's metabolism is getting faster and the flies are becoming less susceptible to the pyrethrum we're using."

Pyrethrum, a plant-based product used in insecticides, can't be used in many parts of Australia because flies are becoming resistant to it. "We're starting to notice that here a little bit now," says Stevenson.

Tracey Taylor of Ants 2 Go says flies are definitely becoming more persistent. "I wonder if they're breeding genetically stronger every year, because I'm almost having to use a can of fly spray on each lousy fly these days."

Taylor says the company's branches in Auckland and Wellington have noted an increase in infestations.

"Our guy in Wellington says business is booming because even Wellington's getting warmer. It's global warming - that's what I put it down to. It's getting warmer so they're breeding more. As the temperatures warm up, even the South Island might be next."

TV "bugman" Ruud Kleinpaste said flies could be developing resistance to insecticide, although he had not noticed the trend in his work. "Creatures that breed a heck of a lot become resistant a lot faster than creatures that don't breed a heck of a lot."

But he was sceptical about global warming creating a spike in fly numbers this year. He says higher temperatures have persisted for longer this year and flies breed more often when it is warmer.

"To pin it on climate change is far-fetched. There's far more ecologically going on with flies than just a little bit of warming of the universe."