13 Mar 2017

The Department of Water Affairs in Maun has embarked on registration and sterilisation of motor boats, dugout canoes and fishing nets operating in the Thamalakane River system and surrounding areas as a way of controlling the notorious weed called Salvania Molesta.

This followed confirmation by the Department of Water Affairs in Maun regarding the presence of the weed in some parts of Thamalakane River in Maun.

If not controlled, Salvania Molesta also known as Kariba can result in poor water quality which will affect wetlands leading to decrease in their environmental value amongst others.

Speaking in an interview, the department’s chief technical assistant in Maun Mr Gift Katorah confirmed that indeed the Salvania Molesta weed was identified in the area along the Thamalakane River stretching between Matlapana ward and the Maun General Hospital territories.

Mr Katorah attributed the spread of this aquatic weed to torrential rainfalls experienced in the northern parts of Botswana.

He said the current water levels were a great aid to the Salvania Molesta as it was able to move far more easily from upstream to downstream taking advantage of the strong water currents. “We encourage members of the public using the river for different purposes to bring their equipment for sterilization before embarking on using them in the river.

We are talking about motor boats, mokoro, fishing nets and others to avoid the spread of this plant,” said Mr Katorah. He said the aquatic weed was first discovered in Botswana in 1948 in the Kazungula region, adding that the weed originates from Southern Brazil.

Mr Katorah said around the 1990s the Botswana government discovered that the Australian government had experienced the same challenge at Lake Mondara.

Therefore the government of Botswana through the help of the Australian government introduced the method where a certain Cyrtobagous salviniae weevil came into use in Botswana.

He said this weevil was introduced in the upper areas of the Okavango River near Namibia where the river system enters the country to begin feeding on the plant. Mr Katorah said the weevil was able to consume parts of this aquatic plant that enabled it to flourish therefore cutting its lifecycle.

He said the weevil was able to produce a caterpillar that was able to consume the stem of the weed completely shattering its lifecycle, and in that manner controlling multiplication of the plant since the weevil specialises only on this plant.

He said some of the effects of the existence of the Salvania Molesta are the fact that other aquatic life can drastically be affected.

He said the aquatic plant acts as an umbrella by floating in the river therefore depriving other aquatic species such as fish and others sufficient light needed by any animal for survival and therefore dying.

Mr Katorah said given the situation in Maun they were well prepared to combat the situation. He said in the past they used to employ temporary employees to remove the plant from rivers where it was seldom seen.

He highlighted that as a department they were working round the clock to come up with the best method of combating the weed where it was spotted in Maun.
Mr Katorah said fishing from place to place encouraged the spread of Salvania Molesta to places that were least expected to be having the weed.

He cautioned about the movement of motorboats in the river sighting that any disturbance of the water contributes to the spread of the weed. Other contributors were animals like hippopotamus and elephants which in their case were hard to control. ENDS