The warm, wet weather that prevailed last summer meant that three generations of locusts were born, each one up to 150 times larger than the previous generation. After over-wintering beneath the ground, the first generation of 2010 is already hatching. And following the wettest August in seven years, the climate is again perfect. The juveniles will spend 20 to 25 days eating and growing, shedding their exoskeletons five times before emerging as adults, when population pressure will force them to swarm.

It is impossible to say how many billions of bugs will take wing, but many experts fear this year's infestation could be the worst since records began – 75 years ago. All that one locust expert, Greg Sword, an associate professor at the University of Sydney, would say was: "South Queensland, New South Wales and Victoria are all going to get hammered."

A one-kilometre wide swarm of locusts can chomp through 10 tons of crops – a third of their combined body weight – in a day. The New South Wales Farmers Association said an area the size of Spain was affected and the Government of Victoria alone forecasts A$2bn (£1.2bn) of damage.

Controlling the bugs involves spotter planes identifying juvenile bands that can be targets for attack by crop sprayers armed with pesticides. But eastern Australia is struggling to find enough pilots to take on all the work.

And the spraying itself comes at a cost. Apiarists have complained that their bees are in danger from pesticides and ecologists fear for the many animals that treat the locusts as a moving smorgasbord. Concerns have also been raised by bloggers and activists that some of the chemicals used could harm humans.