06 Sep 2020

Department of Water and Sanitation in Maun is fighting the salvinia molesta weed, which has infested Thamalakane River.

Salvinia weed, also known as kariba weed, is a free floating weed and it is reported to be a threat to biodiversity.

In a recent interview, the department’s regional manager, Mr Keodumetse Keetile, confirmed that efforts were on going to fight the weed along the river.

He said they had received reports that the invasive weed had spread widely in the river.

Currently, he said they were using salvinia weevils to fight the weed because they did not encourage the use of chemicals. 

A weevil is a prolific breeder with a voracious appetite for salvinia molesta. 

It has been known to eat its way through as much as 90 per cent of a salvinia infestation.

The department intended to protect wetlands of the country especially that the weeds could result in decomposition leading to poor water quality, decrease in environmental value and this could affect tourism industry as well as wetlands.

Mr Keetile said they also regulated the movement of boats to prevent importation and spread of aquatic weeds.

Meanwhile, reports had shown that the department managed to control salvinia since 2002 and it kept the weed constantly at low levels.

The success was mainly due to sustainable monitoring through application of physical and biological control methods.

It was reported that salvinia could form dense vegetation mats that reduced water-flow and lowered light and oxygen levels in the water and as such the stagnant dark environment could negatively affects the biodiversity and abundance of freshwater species including fish and submerged aquatic plants.

The weed invasion also posed a severe threat to socio-economic activities that were dependent on open, flowing and/or high quality water bodies such as boat transport. Ends