CSIRO expert explains fly season Australia 2020

War of the flies: The annual invasion has arrived

If you suddenly have a houseful of unwelcome guests who vomit all over the place and won't buzz off, you're not alone.

No, not the friends and family from inland who love to visit this time of year. They're very welcome, and if yours vomit all over the place it may be time for an intervention.


It's the time of year when most of us reach for the flyspray and wonder where on earth the multitudes appear from.

David Yeates, director of the Australian National Insect Collection at the CSIRO says they're always there. We just don't always notice them.

"Insects are ectothermic - they're cold blooded, and rely on ambient heat to get active," he said.

"When it's cool and windy they're less active, and when it rains they hide under the leaves to wait it out.

"As soon as the weather heats up they get moving and begin their population cycles. If conditions are good their populations can build up quickly.

"The consequence is you see flies on your window pane and think 'where on earth did they come from?'"

The combination of rain and warm weather has meant all insects - especially flies - have plenty of food, as well as warmth.

But before you reach for the bug spray, Dr Yeates said it was worth considering alternatives.

"When you use spray, you kill the fly you're aiming for, but you also kill any of their predators that are around," he said.

"That predator would have killed hundreds of flies in its life if it lived."

He said a healthy ecosystem would balance itself out. One way of encouraging that, short of bringing spiders into your home, is to have a healthy, messy garden.

"Flowers - preferably native - and messy spots are good for insects," he said.

"A lawn is a bit like a desert for insects."

This story War of the flies: The annual invasion has arrived first appeared on South Coast Register.