Australia faces worst plague of locusts in 75 years
Ideal breeding conditions for grasshoppers are
expected to cost farmers billions
Australia's Darling river is running with water again
after a drought in the middle of the decade reduced
it to a trickle. But the rains feeding the continent's
fourth-longest river are not the undiluted good
news you might expect. For the cloudbursts also
create ideal conditions for an unwelcome pest – the
Australian plague locust.
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.
Though locusts move slowly when the sun's up, at
night they can fly high and fast, sometimes
travelling hundreds of kilometres. "A farmer can go
to bed at night not having seen a grasshopper all
year and wake up in the morning to find his fields
full of them," said Professor Sword.
All locusts are grasshoppers, but not all
grasshoppers are locusts. The difference is a suite
of genetic changes that kick in when population
densities cross a critical threshold. In some species,
they produce physical transformations – the desert
locust of North Africa goes from green to black and
yellow, for example – but the Australian plague
locust merely reprogrammes its behaviour, from
solitary to gregarious.
Swarms probably make use of the available food
more efficiently as the leading edge is constantly
pushing forwards into new vegetation. It may be
fear more than hunger, however, that drives the
locusts.
Locusts are highly cannibalistic, says Professor
Sword, and any that stay still too long are likely to
get nibbled. "Swarms are like lifeboats," he says,
forging a gruesome metaphor. "If you're the only
one in the boat, you could easily starve. But if
you've got lots of company, you could be the last to
survive. We call it travelling with your lunch."
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.
The best hope for phasing out the chemicals comes
from research. But the goal, says Professor Sword,
is control not eradication. "They were here long
before humans arrived," he said.
Ideal breeding conditions for grasshoppers are
expected to cost farmers billions
Australia's Darling river is running with water again
after a drought in the middle of the decade reduced
it to a trickle. But the rains feeding the continent's
fourth-longest river are not the undiluted good
news you might expect. For the cloudbursts also
create ideal conditions for an unwelcome pest – the
Australian plague locust.
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.
Though locusts move slowly when the sun's up, at
night they can fly high and fast, sometimes
travelling hundreds of kilometres. "A farmer can go
to bed at night not having seen a grasshopper all
year and wake up in the morning to find his fields
full of them," said Professor Sword.
All locusts are grasshoppers, but not all
grasshoppers are locusts. The difference is a suite
of genetic changes that kick in when population
densities cross a critical threshold. In some species,
they produce physical transformations – the desert
locust of North Africa goes from green to black and
yellow, for example – but the Australian plague
locust merely reprogrammes its behaviour, from
solitary to gregarious.
Swarms probably make use of the available food
more efficiently as the leading edge is constantly
pushing forwards into new vegetation. It may be
fear more than hunger, however, that drives the
locusts.
Locusts are highly cannibalistic, says Professor
Sword, and any that stay still too long are likely to
get nibbled. "Swarms are like lifeboats," he says,
forging a gruesome metaphor. "If you're the only
one in the boat, you could easily starve. But if
you've got lots of company, you could be the last to
survive. We call it travelling with your lunch."
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.
The best hope for phasing out the chemicals comes
from research. But the goal, says Professor Sword,
is control not eradication. "They were here long
before humans arrived," he said.
Comment