Science: Research scientist Hasan Rahmani is the man in the hot-house, carefully breeding the weevils in a tightly controlled environment.
Photo by
Daneka Hill
The best way to fight an alien is to become friends with its enemy.
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Of course this strategy has backfired on us in the past; the legendary cane toad being the most infamous example.
But researchers at Tatura’s SmartFarm are excited about the possibilities of three weevil species from the swamps and bayous of the United States’ deep south.
The weevils are natural enemies of the noxious irrigation channel weed Sagittaria platyhylls, which is particularly prevalent in the Goulburn Valley’s waterways.
Pretty noxious: Sagittaria platyhylls was bought into Australia as an ornamental garden plant. Without any pests or predators, it took off.
Photo by
Daneka Hill
The approval process began five years ago and is still ongoing as scientists ensure there will be no ‘cane toad effect’, according to biocontrol team leader Raelene Kwong.
“In here we introduce the weevil to different native plants and plants of particular significance to see how they react,” Ms Kwong said.
“That’s why it takes so long because we have to work our way through each native species. Then our research is sent off and peer-reviewed.”
The Sagittaria weed is a prolific seeder, able to drop thousands of seeds into the water and send them downriver where they form dense mats of weed matter.
The weevils from its natural environment in the United States have evolved to lay their eggs inside the weed’s flowers and seed pods.
Their larvae then destroys the seeds as they grow and feed on the plant.
“We’ve been looking at three different biocontrol agents,” Ms Kwong said.
“I have a saying about using them, ‘it’s the lesser of two weevils’. Might be time to retire that joke, some of you didn’t laugh.”
Team leader: Raelene Kwong from Agriculture Victoria. Ag Vic is running the tests and is bankrolled by the Victorian Government, Goulburn-Murray Water, Goulburn Broken CMA and other water authorities.
Photo by
Daneka Hill
Research scientist Hasan Rahmani has been mass rearing the weevils in a secure hot-house at the Tatura SmartFarm.
“Their whole life cycle is five to six weeks,” Mr Rahmani said.
“We normally place a plant into a mesh cage where the eggs are laid. Then we incubate the eggs in containers. Spring to autumn is our egg laying season and after a whole week the larvae will emerge and we study the results.”
Once the weevils are approved they will be released in selected ‘nursery sites’ where eggs will be collected and spread to other trouble areas.
Mesh cages: A series of little tents where a selection of weeds is put to feed the weevil population.
Photo by
Daneka Hill
Cut loose: Larvae are incubated inside these airtight containers.
Next threat: Once the Sagittaria is dealt with, studies will move on to fully-submersed weeds, such as these ones which exist in Lake Mulwala and keep washing into the Murray River.
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