error code: 523 Tiny weevils can fight off invasive aquatic plant on SA’s rivers – The Mail & Guardian – Newsglobalarena

Tiny weevils can fight off invasive aquatic plant on SA’s rivers – The Mail & Guardian

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Julie Coetzee, the deputy director of the Centre for Organic Management at Rhodes College, oversaw the discharge of the Cyrtobagous salviniae organic management agent into the Crocodile River.

A tiny weevil species has been launched into the Crocodile River close to Hartbeespoort to deal with the unfold of the widespread salvinia, an invasive alien aquatic plant that may be a rising menace to South Africa’s freshwater ecosystems.

On Monday Julie Coetzee, the deputy director of the Centre for Organic Management at Rhodes College, oversaw the discharge of the Cyrtobagous salviniae organic management agent into the Crocodile River. 

The 2mm-long weevil species is a subaquatic herbivorous insect that feeds on the widespread salvinia (Salvinia minima), which is native to South America.

Since first being recorded at Hartbeespoort Dam in 2011, salvinia has unfold throughout varied water our bodies in North West and Gauteng and has prolonged its vary to the Limpopo River, which kinds the nationwide border with Botswana. 

“If we don’t management this plant, whether it is allowed to unfold, we’ll see it shifting into increasingly more water our bodies throughout the nation. Sadly, it thrives in polluted methods,” famous Coetzee, who was joined by the deputy minister of water and sanitation, Isaac Sello Seitlholo

This plant, and different invasives prefer it, block out the daylight from the water physique, which reduces oxygen, she stated. “Crops in that water physique received’t be capable of create oxygen via photosynthesis. If there’s no oxygen, there aren’t any fishes, no crabs, no bugs. It fully destroys or alters the aquatic ecosystem.” 

Salvinia is on the transfer within the nation’s waterbodies.

“We first recorded it round Hartbeespoort Dam and we’ve step by step been discovering it in additional of those Highveld dams. It was on Bon Accord Dam close to Pretoria, Roodeplaat Dam, Bronkhorstspruit Dam after which we discovered an enormous infestation on Bospoort Dam, which is on a distinct river — the Hex River, simply north of Rustenburg,” Coetzee stated.

“The Hex river flows into Vaalkop Dam and Vaalkop now has an enormous salvinia minima drawback on the Hex River itself after which Vaalkop overflows into the Elands [River], which joins the Crocodile, after Roodekoppies Dam, so now Roodekoppies Dam has acquired some salvinia minima from Harties.”

Vaalkop and Roodekoppies are close to one another and be part of within the Crocodile River. “Then it flows all the way in which to the Limpopo River on the border with Botswana and we discovered it within the Limpopo River as nicely. 

“And the issue with that’s that it’s on our  border with Botswana; it’s going to movement into Zimbabwe, so it’s a little bit of a difficulty … We must always have a mandate to manage something coming downstream from our invaded methods.”

Partly via Rhodes College’s Centre for Organic Management, Coetzee has carried out intensive analysis over a number of years to consider the efficacy of Cyrtobagous salviniae as a organic management agent for salvinia. The centre was granted approval for launch of the insect late in 2024.

“It’s utilized in Florida [United States] fairly extensively and so they don’t actually regard salvinia minima as a lot of an issue plant anymore. We all know from that success, that we’re extremely prone to get success in South Africa as nicely,” she stated. 

The weevil was imported from Louisiana within the US, which additionally battles Salvinia minima

“We’ve launched a small starter inhabitants,” Coetzee stated of the 150 bugs that have been unleashed on Monday. “However what we will likely be doing is rearing them at rearing amenities. Now we have one at Rhodes College in Makhanda.

“Now we have additionally arrange neighborhood rearing stations round Hartbeespoort Dam, Vaalkop Dam, and Bronkhorstspruit. Now we have lots of neighborhood companions who’ve realised the worth, the sustainability and the cost-effectiveness of those bugs.”

One other batch of 100 bugs was put right into a rearing station at Lakeland, an property at Hartbeespoort that’s “already rearing the water hyacinth management brokers [the water hyacinth hoppers] for us”.

Seitlholo applauded Coetzee and her crew for the way in which they have been tackling the salvinia drawback “firstly of a price chain”.


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