A tiny, ravenous beetle is set to devour tonnes of one of the world’s most dangerous water weeds – averting a potential existential threat to the local aquatic ecosystem.

Salvinia molesta, a type of invasive aquatic plant also known as Kariba, Kariba a weed or giant salvinia, is a free-floating aquatic fern , has invaded Poplar Dam in Wavecrest, Jeffreys Bay – already covering more than 90% of the dam’s surface. But there is hope for the dam, and it comes in the shape of a small, innocuous-looking but remarkably powerful water-dwelling beetle.

Kouga Municipality, in conjunction with the Centre of Biological Control (CBC), is set to use cyrtobagous salviniae weevils – which is being reared not too far from the dam – to control the spread of salvinia molesta at the specific dam.

This forms part of the greater Invasive Alien Management Plan for the dam.

“Currently, common salvinia is running rampant at Poplar Dam, and the newly-reared weevil will be used to combat this invasion,” said Kouga Executive Mayor, Horatio Hendricks.

Using weevils is a highly effective biological mechanism of controlling salvinia. The Biological control is a long term sustainable natural process that has worked at many sites all over the world. It is also cost-effective and environmentally friendly

“Tested under quarantine conditions to ensure its safety, the weevil is host specific, thus it can only carry out its life cycle on salvinia.”

According to Hendricks, the municipality, with the support of a local resident, will mass-rear the weevil over the winter period, before releasing it onto the invaded site in spring.

“The insect does not do particularly well in shaded areas as it is from the tropics and prefers heat,” said Hendricks. “The municipality will thus trim and remove some of the pine trees surrounding the dam.”

He said the management of the salvinia at Poplar Dam is an ongoing process, and the municipality is continuously assessing the options available to control the spread and density.