Once again a plague of locusts is descending on Australia. This time it could be a rare native fungus that defends us from agricultural disaster. But the Metarhizium fungus loves the damp, while the locusts love the dry. And only 2 locusts have ever been reported killed by the fungus out in the wild. The journey from microscopic curiosity to white knight has been long and difficult; but this year, for the first time, this fungus is on the frontline.

TRANSCRIPT

Narration
Mudgee in central NSW is famed for its wine and honey.

But now it's under siege by a bunch of nymphomaniacs who'll eat you out of house and home.

The so called bands of marching baby locusts OR NYMPHS look like a dirty stain .

And the best hope to clean them up lies with a rare fungus most experts thought wouldn't even work

Dr Richard Milner
Most of us I think were sceptics. We thought well of all things to use a fungus to control locusts which are very dry country organisms seemed to be a crazy idea.

Narration
Around the world and especially in Africa - locusts like the green feed of intensive agriculture where there tend to be people and towns.

Organophosphate pesticides can have side effects so in the early 90s an international push began to find a substitute.

And interest soon focused on a fungus called Metahizium which had a particularly soft spot for locusts..

Chrisopher Zinn, reporter
Metarizhium is common in soils around the world but the Australian strain we are interested in is very rare in fact its almost an endangered species . In the wild only two locusts have ever been found which were killed by it

Narration
In Queensland in 1979 a farmer found one and thoughtfully handed it in. A fungus was cultured and stored but no one knew what they had until early tests showed its virulence to the dreaded Australian plague locust.
Metarizhium spores literally bore into the locust's cuticle or skin.

They steal water and nutrients and grow little tubes that burrow further eventually killing the insect

Dr Richard Milner a now retired CSIRO entomologist is an expert on fungi that attack insects. He worked on the project for a decade

Chrisopher Zinn, reporter
It's not very large is it?

Dr Richard Milner
No it's a small insect but it has a great capacity to breed up(cut).

Narration
Richard was excited by the possibility of a selective bio pesticide which TOOK out their target but didn't hurt the good guys.

Dr Richard Milner
These are so called Petagonid Longhorn Grasshoppers, and they're actually beneficial insects. They're predators on other insects these grasshoppers. And we got one killed there and they're very very difficult to kill with Meterhisium. (cut)

Narration
A good idea is one thing but mass producing a rare fungus and putting it to work economically in the real world is quite another .

And Richard found hot Australian conditions knocked the spores for six during field trials in the later 90s.

Dr Richard Milner
So we very carefully took it down to Cooma in an air conditioned car. And then we arranged with the publican, the local pub to put it in his fridge overnight to make sure that it didn't deteriorate too much (EDIT) It was 40% viable which was okay. We put it in the plane and sprayed it and brought some back and you know it had dropped from 40% to 2% by putting it in to the plane.

Narration
Worse the spores quickly died on the ground.

The secret after lots of experimentation was to dry them at a very low humidity for a long time.

Dr Richard Milner
And that stabilizes the fungus extremely well. And now it will survive for several years in storage.

Narration
But the scientists say it's NOT persistent in the environment meaning after two weeks the spores are gone.

Yet a fundamental issue still had to be faced

Chrisopher Zinn, reporter
To keep locusts out of valuable places like this vineyard metarizhium seems to be the perfect answer but first there was a problem . Locusts like dry environments and fungus likes damp ones so how on earth do you get and keep the two together?

Narration
The answer came when they tried to mix the spores with water for spraying -they just don't-but in a vegetable oil the spores form a lovely suspension which also protects them from the sun

Dr Richard Milner
The fungus has a great affinity for oil. And by putting it into oil you can spray it on under very hot conditions. It won't dry out and it will still infect and kill locusts under the conditions which I would have thought were not suitable for the fungus to infect insects.

Narration
However It must be used early as its only effective against the hoppers in their nymphal stage before they sprout wings.

It also takes 10-14 days to kill 'em

Ecologist David Hunter spent years developing the fungus with the Australian plague locust commission.

David Hunter
A Well these were sprayed about four or five days ago, and so the fungus has got on the outside of them and is growing inside them now(edit) So it takes a while to work, but it's just because the spores are so very small and they have to grow and put the fungus through the whole insect (cut)

Narration
The fungus developed by the CSIRO has just become available as GreenGuard.

At 40,000 million spores per gram and you need to land 500 spores on each locust to kill it

It costs a mite more than chemicals but for farmers who want to keep their organic status there's just no choice

David Hunter
The real point is that this is a natural thing in the Australian environment anyway, and so all that you're doing is bringing a bit more into the environment

Narration
Avoiding chemicals can also help the birds and the bees.

This Mudgee seed farm needs its bees for pollination so they tried Metarizhium against the hopper infestation

Christopher Zinn, reporter
So when did you spray here Davidl?

David Hunter
Oh I'd say about eleven days ago and it was just fully crawling with locusts. And as you can see now there's none.

Christopher Zinn, reporter
So where have they all gone David? I can't see any of the bodies.

David Hunter
Well normally what happens in these situations is that the ants get them and you can see a few ants crawling around through here, even on this cooler day.

Narration
In Mudgee the locusts deadly nemesis is doing its bit around sensitive areas but because of cost and timing chemicals will still have to be used.

However there will always be locusts and as organic produce become more popular and industrial pesticides less so Metarizhium will never be a rare fungus again.

Dr Richard Milner
Well it's very exciting, because we're now recognised as being the leaders in this area in the world. Australia is now making the most use of this particular fungus and it's likely that in the future we're going to have export markets to places like China, to USA, to Mexico, perhaps even to Africa.

Story Contacts

Dr Richard Milner
Honorary Fellow
CSIRO

David Hunter
Former Plague Locust Commission

Related Info

Australian Plague Locust Commission

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