Hyacinth takes over dam
CANOPY: DELTA PARK WATER BODY COVERED BY INVASIVE PLANT AFTER LENGTHY SEWER LEAK
Planthoppers are released to eat and kill spreading species.
Shirley Tebbutt is making every effort to remove the water hyacinth plant that has completely covered the Delta Park dam as a result of a sixweek sewer leak.
Recently, members from the South African Institute for Aquatic Biodiversity and the Centre for Biological Control, Prof Julie Coetzee, Dr Kelby English, Kim Weaver and Nicolas Salinas visited the dam and released the planthopper, megamelus scutellaris, into the dam.
The hoppers are expected to eat and kill the plants. They feed on the plants by inserting a strawlike mouth part that allows them to suck up the plant’s sap. In so doing, they also introduce plant diseases caused by fungi and bacteria. The plant gradually starts to die and stops producing flowers and daughter plants.
About 25 000 hoppers were recently released into the dam. Coetzee said the biological control takes time. “It is not a quick fix, but if we get enough bugs onto the system, particularly in spring when the plants start to regrow, we could see a significant reduction within a year.”
She said it was important to know that biological control did not aim to eradicate the invasive plant but to get the population to an acceptable level of control.
If this can reduce the hyacinth cover by 85%-90%, it will be considered an excellent result.
“We will continue to release the hoppers as long as we can keep supplying them from our mass-rearing facility at Rhodes University,” she said.
“We would ideally like to set up a rearing station at Delta Park that could continually supply the dam with bugs, but there are all sorts of logistical constraints to that, the biggest being theft.”
Tebbutt said the hyacinth did not root in the sediment as it was floating and removing it had become too big and complicated for her and her team.
“This is a job that’s way too big. Unless someone gives us R20 000 or R30 000, I will have to find people who know how to swim and know about these plants. This is a disaster.”
Manual removal can help to keep key areas of the dam clear but takes a lot of effort to do so. Chemical herbicides are also available for water hyacinth control.