About a third of the Hartbeespoort Dam is currently covered by hyacinth plant but the plants are showing signs of damage due to the biological control bugs.
“Although plants still look green and healthy from a far, upon closer inspection the plants are undergoing high levels of damage. This increase in biological control numbers is positive, considering the cool and wet weather that Hartbeespoort dam has been experiencing over the last few weeks. The number of agents counted on the dam during this month is comparable to January 2021,” the Centre of Biological Control of the Rhodes University said this week.
The team visited the dam last week to monitor the growth of hyacinth and the biological control bugs, M. scutellaris, on the plants.
Between October and December 2021, 64 400 Megamelus scutellaris from the CBC mass-rearing facility was released onto the dam. Particular sites includes the Coves, Lakeland, Pecanwood, Ifafi Senior Club and Cosmos Marina Club. In addition, 11 120 Megamelus were released from satellite stations located around the dam. “We commend all our stakeholders and the community members who made this possible.”
On 16 January, the estimate cover was 37% (over 614 hectares).
“Our latest monitoring data (15 January 2022) indicate that the biological control agents are thriving in huge numbers on water hyacinth. Our data shows that there is currently 4 600 M. scutellaris individuals present per square meter. This is a rapid increase, considering that M. scutellaris numbers were only 109/m2 in November 2021. We also measured high numbers of Neochetina spp. weevils.
Researchers from the CBC will continue to monitor biological control agent populations and water hyacinth on the dam during the coming weeks.