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South Africa uses insects to fight invasive species

May 11, 2022

Can planthoppers help fight the spread of water hyacinth in South African waterways?

A boat entrapped by the aquatic week at a jetty in Hartbeespoort Dam in South Africa’s North-West province
Hyacinth for over 50 years in Hartbeespoort Dam in South AfricaImage: Jason Boswell/DW

Planthoppers versus water hyacinths

Water hyacinth, an aquatic weed from South America, is widely regarded as one of the world's most problematic plants. 

It has spread across the globe and invaded local waterways, making them difficult to access. It also presents an environmental challenge by outcompeting native species and creating a dense mat of leaves across the water's surface that prevents sunlight from reaching plants and animals below.

Since arriving in the early 1900s in South Africa, water hyacinth has spread throughout the country. Attempts to control its growth using chemical herbicides or removing it by hand or machinery have had little impact. 

A water hyacinth planthopper, Megamelus scutellaris, sits on a hyacinth leaf showing the damage inflicted on the invasive plant by the insect
The planthopper has proven to be an effective biological control agent against the invasive plant in South AfricaImage: Jason Boswell/DW

In 2019, the Center for Biological Control(CBC), part of Rhodes University in the country's Eastern Cape Province, introduced a new tool in the fight to control the invasive species: a native insect called the planthopper. 

Since 2019, the CBC has bred over 1 million planthoppers at a special facility and put the insect army into action on the Hartbeespoort Dam, where hyacinth covers more than 40% of the surface area of the water. 

A film by Jason Boswell

An aerial viewing showing the vast mats created by the free-floating weed
The plant accumulates in certain sections of the dam effectively blocking out sunlight and clogging the waterway for boat trafficImage: Jason Boswell/DW
Jason Boswell Jason Boswell is a reporter based in Cape Town, South Africa.