They’ve got the Dusi bugged | Mercury article 10/01/12

Hyacinth concerns for Dusi canoeists
Copy of Copy of NM Dusi bugs1 
 Picture by Bart Fokkens of DUCT 

Will the water hyacinth cause this year’s Unlimited Dusi Canoe Marathon to choke?
While his team was putting measures in place to eradicate the problem, race organiser Ray de Vries said they were concerned about the blockage the water weeds, the fastest growing weed on the planet, had formed at the top of Inanda Dam.
“It is so dense that it would force paddlers to get out of their canoes, take to land and walk,” he said. “With temperatures reaching 40°C, this would be unacceptable.”
He said that organisations like the Dusi Umgeni Conservation Trust (Duct) were working hard to solve the problem.
De Vries said that while infestation was always a problem, it was especially bad just as summer began – water hyacinth has been a problem in the river since the early 1900s.
“The increased heat and humidity cause the plant to flourish,” he said.
He said that usually the heavy rains would flush the river clean, but because of the blockage, all the weeds that were uprooted and washed away would add to the blockage.
“Hand-spraying is just not going to work – so we’ve enlisted the help of a helicopter that will spray the weeds, kill them and cause them to sink, relieving the blockage,” he said.
Implementation manager at Working for Water Ryan Brudvig said that the dead plants usually took two weeks to sink but the team, consisting of the Department of Water Affairs’ initiative Working for Water, the eThekwini Municipality, Umgeni Water, the Dusi Umgeni Conservation Trust (Duct) and the South African Sugarcane Research Institute, had started early because they had a large area to tackle.
The team, he said, had started removing the hyacinth mechanically in December.
Last year Brudvig blamed effluent from factories and sewage works which had acted as “fertiliser” for the plants.
Special water weevils have been enlisted to assist in the fight against the alien invasive species.
The hyacinth moth, Niphograpta, the hyacinth-specific Neochetina weevil and the water hyacinth mirid Eccritotarsus catarinensis, (which sucks chlorophyll from the leaves), were introduced last year – the insects target water hyacinth and do not eat indigenous flora.
De Vries said that this was the reason the water from Blue Lagoon to the Dam was clear for the “first time in years”


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