Bio-control agents deployed in river hyacinth war

The next battle to win the ongoing war against water hyacinth to rescue the Toti River is being waged.

Now that most of the river has been cleared of hyacinth, the next step is to spray and introduce bio-control agents.

“Mark Pontes of Toti Canoe Club contacted me about three months ago to ask for assistance in managing the infestation of water hyacinth on the Toti River using biological control,” said the biological control and aquatic weeds officer for coastal KZN, Karen Hope. “I made a request to the commercial biocontrol mass-rearing facility at SASRI for bio-control agents.”

The bio-control agents in this case are the stem-boring weevils, Neochetina bruchi and N. eichoniae, two of eight available for water hyacinth in South Africa.

“The day before I was due to release the agents onto the Toti River, I received an email informing me of eThekwini Municipality’s decision to manually clear the plants from the river and a few other rivers in the vicinity, using local labour as a way of poverty-alleviation and skills development.”

After a meeting with the canoe club and municipality, Karen agreed the parks department would do the clearing and thereafter she would release the bio-control measures to manage any plants that were either missed or germinated after the clearing. “We did the first spray on Saturday morning,” said Mark. “We use midstream to spray on top of the plants as they pop up and it will be an ongoing project, with a monthly spray cycle.” The chemicals are supplied by council, but Mark and his team use a rubber duck to reach the plants and he hope a regular spray will keep the water hyacinth at bay, although it is being well-fed with all the nutrients in the water. “In the water sample test we did, the results were very bad – with over 7,000 particles of sewage per millilitre, which is unacceptable.

We thank the Army Saints and public support for being the real heroes of the day. Half the battle is already won,” said Mark.

“We had about 20 people who pitched in to help with the river and lagoon clean-up on Sunday,” said sergeant Justine Purcell.

“We noticed the river has started flowing again and washing clumps of water hyacinth down stream. Most of the lagoon has been cleared, so the next step is to ensure it remains hyacinth-free in the future.”

The Saints thank Tommy Ackerman senior for making them boerewors rolls for lunch. “We are winning it seems,” said Army Saints founder, Shaun Callaghan. “We were able to paddle from Toti Lagoon to about 100m past the Hutchison Road bridge. Along the way we saw two goliath herons, six Egyptian geese, three cormorants and a ton of small birds. The water was pretty clean and only smelling in a few places.”

Army Saints will meet at 10am on Sunday, 29 June to clean the river behind Toti Rugby Club, with another group cleaning the river at Warnadoone Lifesaving Club.

Everyone must take along gumboots and gloves, as the water is unsanitary.