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Tuesday, March 21, 2023

Scientists unleash ancient enemy to control invasive weeds in ‘World First’

Scientists in Australia are hoping to combat an invasive aquatic weed by unleashing an army of weevils, the plant’s natural enemy.

Researchers from Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) have teamed up with one of the country’s largest water companies, Seqwater, to release the Diddy defenders and contain the spread of the invasive Cabomba plant.

“It’s a world first,” Kumaran Nagalingam, senior research scientist at CSIRO, said in a statement. “There is no organic control program [for cabomba] what is happening in other parts of the world.”

cabomba, Cabomba caroliniana, is a fast-spreading weed introduced to Australia from South America in the 1960s. “Unfortunately, it was such a pretty plant that it was brought into the county as an aquarium plant and somehow escaped the aquariums and made its way into our waters,” said David Roberts, a senior scientist at Seqwater, in a statement.

Cabomba may look attractive in an aquarium, but once released into the wild, it can wreak havoc on native plants and animals.

“It outperforms all of our native plants that used to live in the lakes, and it can also affect animals because they don’t like living in such dense plant material,” Roberts said.

“Cabomba grows up to 5 cm [nearly 2 inches] per day, strangling native ecosystems, choking waterways and affecting native aquatic animal and plant populations,” added Nagalingam.

The weed also blocks intakes and plumbing, posing a threat to boaters and swimmers who can become entangled in its vines.

For more than 20 years, the research team has been looking for the natural enemies of the plant in their home country of Argentina. “Cabomba does have some natural predators associated with it, but one thing we need to make sure is that they’re unique to Cabomba — it doesn’t eat or duplicate with other native plants,” Nagalingam said.

Eventually, they settled on the Cabomba weevil, a creature smaller than a grain of rice. The weevil attacks the plant at different stages of its life cycle: the larvae tunnel deep into the plant’s stems, while the adults feed on the plant’s leaves.

Although the researchers don’t expect the weevils to completely eradicate the cabomba, hopefully they will reduce the plant’s thickness and size and keep its growth in check. This avoids the use of harsh chemicals and expensive manual weeding to keep lakes clean and healthy. According to Seqwater, it costs about $170,000 a year to manually remove Cabomba from three lakes.

To avoid unknown diseases accidentally entering the water, the imported weevils were quarantined and carefully screened for parasitic hitchhikers before release.

They will be tested in Lake Kurwongbah near Brisbane, Queensland before being released in other lakes across the country. Seqwater will continue to raise the tiny soldiers in a purpose-built “weevil nursery” for future potential releases.

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