Author: Selwyn Jackson
Roodeplaat Dam is situated 22km north-east of Tshwane and is the main rowing venue in Gauteng, often referred to as the home of South African rowing. The dam caters for 1000m races and 2000m races and is the venue for the main championship regattas in South Africa. The World Masters Regatta in 2023 will be held at Roodeplaat Dam.
Biological control at Roodeplaat Dam
Roodeplaat Dam has struggled for many years with Water Hyacinth (Eichhornia Crassipes). Water Hyacinth is frequently branded as the world's worst aquatic weed due to its invasive potential, negative impact on aquatic ecosystems, and the cost it necessitates to control it. Over the past two decades, the Department of Environment Forestry and Fisheries (DEFF) together with the Centre for Biological Control (CBC) at Rhodes University has introduced a number of biological control agents at Roodeplaat Dam to control the Water Hyacinth. These bio controls target only the Water Hyacinth and do not affect other plants.
In addition, manual spraying and removal of the Hyacinth using pitchforks has helped keep control of this invasive species and ensure that training and regattas can continue to be held at the dam.
Impact of COVID-19 on Roodeplaat Dam
In March 2020, the Planthopper (Megamelus scutellaris) was introduced and initial results showed that the scales may finally have tipped in controlling Water Hyacinth.
AND THEN COVID-19 ARRIVED!
The Covid-19 pandemic resulted in South Africa going into lock-down level 5 at the end of March. For months, pandemic restrictions meant no-one could visit the dam and control the growth of the Water Hyacinth.
Over the space of a couple of months, the Water Hyacinth had overrun the dam and destroyed our course!
As soon as lock-down restrictions were eased (around end of September 2020), the team under Selwyn Jackson, put together a plan to recover the course and eliminate the Water Hyacinth problem.
Recovering the Roodeplaat course
Teams of volunteers from the rowing community, went out over many weekends to decommission the course. Lanes were intertwined and overrun with Water Hyacinth; trees had drifted into the dam around which lanes and buoys were tangled; everything had to be removed.
Selwyn's team recovered as much of the course equipment as possible, and purchased additional equipment to make up the shortfall. The equipment arrived in January, but before the new lanes could be installed, the Water Hyacinth problem had to be tackled.
Winning the war against Water Hyacinth
The following bio control agents are present at Roodeplaat Dam:
- Larger weevil Neochetina eichorniae
- Smaller weevil Neochetina bruchi
- Mirid Eccritotarsus catarinensis
- Moth Niphograpta albiguttalis
- Planthopper Megamelus scutellaris
Although the bio control agents had shown positive results in March 2020, the sheer volume of Water Hyacinth by December 2020 was too much for these bugs to tackle without some help. On 17th December 2020, a sub-lethal spray of Glyphosate herbicide was applied by DEFF to the main body of the dam away from the banks. This spray did not kill the Water Hyacinth outright but stunted the growth and prevented the Hyacinth from flowering. The Glyphosate is absorbed by the Hyacinth and it migrates to the growing parts of the plant - the bulb and roots.
The bio control agents were not affected, but as the plants died off, the bio control agents moved to more healthy plants. Four weeks after spraying the Water Hyacinth coverage of the dam reduced from 65% to 12%. The concentration of the bio control agents increased dramatically on the remaining plants.
The bio control agents do not increase at the same rate as the Hyacinth, so rearing stations are used to supplement the bio controls on the dam.
Rowing South Africa announces 2021 National Regatta
Work commenced on installing the course from the middle of February. At the end of March, Rowing South Africa announced that the National Senior Regatta would take place the first weekend in May.
Now it was all hands on deck! Not only did all the lanes have to be laid and tensioned, but lots of hyacinth needed to be removed manually to help the bugs be more effective.
In the space of six weeks, what had seemed an insurmountable challenge was achieved and the course was ready! By 20 April, the hyacinth coverage was down to 1.8% from a peak of 65%.
On 1st and 2nd May, South African rowers participated in the first rowing event in over a year. To allow the regatta to go ahead, Rowing South Africa had to implement extra measures to ensure all athletes remained compliant with current COVD-19 regulations. All athletes were incredibly receptive and compliant. The regatta was been hailed as brilliantly organised by all sporting federations.
Congratulations to the rowing community in South Africa
The progress that has been made this year at Roodeplaat Dam was due to the rowing community pitching in and helping wherever possible. This kind of determination, energy and commitment augers well for what promises to be a fantastic World Rowing Masters Regatta in 2023.
- Biological Control at Roodeplaat - Selwyn Jackson, February 2021