Brought to you by La Trobe University’s Research Week, a series of lunchtime talks where we celebrate our research excellence. This year’s focus is engagement and the impact of our research.
When you think of Australia’s Most Wanted, who comes to mind? Ned Kelly? Chopper Read? Someone like that?
Here are some clues. The criminal suspect is small, slender, yellow, erratic and devastating. For 60 years it has wreaked havoc, running through ecosystems, building super colonies and leaving a trail of destruction in its wake. It’s a global menace, spreading its brood and decimating local vegetation, crops and wildlife. And over the years it has killed tens of millions on Christmas Island.
It’s the yellow crazy ant, and authorities have been powerless in their fight against it.
From the time Captain Cook landed at Botany Bay in 1770, Australia has become home to many destructive species. But nothing tops the yellow crazy ant, ranked among the world’s 100 most-invasive species. It’s a global scourge that needs to be slowed and contained.
On Christmas Island, yellow crazy ant super colonies are out of control, with countless millions of the island’s iconic red crabs falling victim to a deadly method. The crazy ants spray acid on the crab, which produces two outcomes. Either the creature dies from dehydration or the ants tear it to shreds.
Something had to be done.
Enter Dr Peter Green, Head of Department at La Trobe University’s College of Science, Health and Engineering. Dr Green has produced results in the asymmetric battle to curtail the powerful species. He’s enlisted an ally, a 2mm-sized Malaysian micro-wasp known as the Tachardiaephagus somervilli.
The wasp was a good choice for biocontrol because it only exhibits predatory behaviour toward one species, none other than the yellow lac scale insect, which produces honey dew.
Honey dew is the yellow crazy ant’s main source of food.
That makes the micro-wasp super valuable.
Who can forget the colossal blunder that was the Cane Toad? Introduced to Australia in 1935 as a biocontrol method for taming the Sugar Cane Ravaging Beetle, this little amphibian species was an unmitigated disaster.
After its introduction, predators began to prey on the toad. But the poisons it secreted were deadly. Soon, wildlife numbers for birds, snakes, lizards and other Australian predators went into rapid decline.
Today, the Cane Toad is one of the country’s worst invasive species.
So when Dr Green, in partnership with Parks Australia, enlisted the services of the Malaysian wasp, they made sure the method would not affect local wildlife, vegetation and nests.
The Malaysian wasp was the perfect fit, a viable biocontrol method that won’t scale out of control and could potentially curtail crazy ant growth.
Researchers had their champion.
How the wasp works
Think of the lac scale insect as a sort of all-you-can-eat buffet for crazy ants.
For years, the crazy ant has been gluttonously feeding on honey dew.
The insect sucks up sap from trees, then secretes honey dew, making an offering that’s irresistible to the crazy ant.
The result was a biological nightmare for Australia.
For years, the crazy ant has been gluttonously feeding on honey dew. This creates the equivalent of crazy ant colonies on steroids. Because no predators exist to kill lac scale insects, they’ve been able to supply crazy ants with a super abundant food source.
In response, Dr Green’s plan is simple. With Parks Australia, he spread 18,000 wasps across four crazy ant super-colony sites on Christmas Island. The goal wasn’t to eradicate the crazy ant, but to contain its seemingly unstoppable spread.
By laying its eggs inside fully mature lac scale insects, the wasp will ultimately dwindle the population size of the insect, which then slows crazy ant population growth.
By the way, the lac scale insect isn’t native to Australia. It’s yet another invasive species. So, metaphorically, Dr Green and Parks Australia will kill two birds with one stone.
It’s a win-win situation.
Although signs are promising, it will take many months before the wasps have a significant impact. Once the lac scale insects have significantly reduced, we expect to see a drop in crazy ant numbers.
According to Dr Green’s research, the wasps are not only surviving but spreading. They’ve been able to successfully lay eggs inside lac scale insects without a deadly reaction from the crazy ants.
Dr Green says, “Although signs are promising, it will take many months before the wasps have a significant impact. Once the lac scale insects have significantly reduced, we expect to see a drop in crazy ant numbers.”
No doubt farmers, ecologists and environmental experts worldwide will applaud when that happens. And that’s testimony to La Trobe University’s groundbreaking scientific research, aimed at solving some of the world’s most pressing issues.
Want to learn about insect ecologies and the ways they interact with the environment? Enrol in a Bachelor of Science at La Trobe.