Efforts by the Dusi Umgeni Conservation Trust (DUCT) to restore the health of Durban’s uMngeni River between Midmar Dam and Blue Lagoon are paying off – and it comes just in time to make life a little easier for paddlers during the Unlimited Dusi Canoe Marathon starting on 16 February.
Limpopo grass has been able to completely straddle the uMngeni River in places (see picture above), using floating beds of invasive alien vegetation, such as water lettuce and water hyacinth, for support. But a combination of manual labour, herbicide and the deployment of armies of biocontrol agents has cleared a pathway in the uMngeni River in Durban’s Reservoir Hills area for the first time in years.
Last year, DUCT field manager Bart Fokkens released thousands of South American weevils in the river. These weevils feed on the invasive plants. Reared by the SA Sugar Research Institute, the weevil population bloomed after the cold winter.
“The level of infestation is magnificent,” said Fokkens. “We’re seeing up to nine weevils per plant. The leaf damage is phenomenal.”
DUCT also hired an amphibious tool-carrying vehicle to cut a path through the floating carpet at Reservoir Hills last year. Then a team of 17 labourers moved in, cutting and hauling 140t of biomass and setting it up in windrows on the river’s edge to compost.
“The floods in December pushed the biomass into Neptune’s Garden. That was the end of the compost, but at least the river is completely open,” said Fokkens.