Eco tourism operator Chobe Holdings Limited has scaled up efforts to assist the department of Water and Sanitation in the control and management of Salvinia weed in some parts of the Okavango Delta that it operates. This is hot on the heels of the recent observations on the widespread of the weed’s proliferation in the Delta.
The company through its subsidiaries, Ker and Downey and Desert and Delta Safaris, under the Salvinia Weed Project established salvinia weevils breeding tanks in key sites – Camp Xakanaxa in the Moremi Game Reserve and Kanana up in the Xudum system due the seriousness of the threats posed to the areas and their downstream.
Salvinia Weed or Salvinia molesta, an invasive aquatic plant that poses threat to the ecosystems’ biodiversity, if left uncontrolled takes over water bodies and suck life out by reducing the amount of dissolved oxygen. The floating weed’s mats have also been blamed for channel blockages, leading diversion of water flow.
The infestation can also have devastating effects of human or economic activity on the watercourses infested leading to disruption in livelihoods.
To keep the weed under control, the use of a biological control method, salvinia weevils is currently trusted for effective control.
Chobe Holding Environmental Manager Segametsi Monnamorwa has been instrumental in seeing through the group’s Salvinia Weed Project in all the key selected sites.
She recently told The Ngami Times that of the two sites, Xakanaxa was key, particurly that the proliferation of the invasive plant in lagoons within the area had been unprecedented, threatening the entire system that connects Khwai, while the Xudum flows towards the Buffalo fence and could join the Thamalakane system during high floods and the consequences of the weed spreading downstream would be dire.
After overseeing the breeding of the weevils at Xakanaxa site – Monnamorwa was this week in the area to perform the final phase of releasing the them into the infested areas.
While in Xakanaxa, Monnamorwa undertook transects to re –valuate the level of the invasion in the different lagoons in the area, among them Jesse’s pool 1 and 2, all the small channels feeding both Jesse’s pools 1 and 2 one and two, paradise pool, Lagoon around the old DWNP boat station
A further boat transect was undertaken in the main channel up to the mokoro station, and ended due a blockage at the 7 kilometre point.
“From the boat transects, Boat Transect Findings, there were still isolated pockets of the alien invasive plant in the channel, the fresh and newly forming Salvinia molesta was mostly found in shaded isolated pockets of the channel. The bigger isolated sections infested with fresh salvinia molesta were seeded with the weevils for control. The Salvinia molesta found on the edges of the channel was mostly dead, probably due to the recurring heat wave. Fresh Salvinia molesta was collected from the mostly the isolated pockets within the channel to establish the feeding stock tank,” Monnamorwa reports.
From the road transects to lagoons mentioned above, Monnamorwa revealed that they did not have large infestations of fresh Salvinia molesta.
“Resurgence of Salvinia molesta is anticipated with temperatures dropping and water levels rising a bit from the local rain. The teams on the ground will be undertaking weekly checks and scout for resurgences. Weevils bred in the lodge will be collected and handful of weevils dropped around the active isolated patches within the channel and at the infested pools,” she said of possible resurge of the weed.
One of the observations made, she said, was that the harsh weather conditions of extreme heat may have had a negative impact on the breeding process of weevils.
Meanwhile, staff training on the whole salvinia project remains crucial for day to monitoring and execution of action plans for the success of the operation.
To this end, Monnamorwa said Camp Xakanaxa General manager Andrek Ditsaro has been responsible for ensuring the pools are well managed to keep the breeding of weevils ongoing.
“Mika Tenego (Groundsman) and Joel Forembi (Maintenance personnel) were involved to get the us to all the Salvinia molesta sites. They were also hands on the dropping of weevils in the channels. Mike and Joel have been involved in this project before, so they have their prior knowledge and a very good understanding of this project, “she said.
Meanwhile in Kanana, on the Xudum system Monnamorwa reports that from the road transects conducted this week, it was evident that surface water has receded quite significantly in both the e lagoons and channels, resulting in the significant reduction of the infestation of the alien invasive plant around the camp.
“Weevil breeding tanks were set up for the long-term management off the alien invasive plant. Weevils fetched from Xakanaxa were dropped in lagoons that were largely infested. It is also anticipated that the increase in water levels from the local rain may result in resurgence of the alien invasive plant. Therefore, ongoing site monitoring will be undertaken by camp teams,” she said.
Previously, Monnamorwa had in an interview underscored Chobe Holdings Limited’s commitment to ethos geared towards sustainability in environmental conservation, which have been the bedrock of its operations in the sensitive ecosystems it operates.
Monnamorwa highlighted that the salvinia molesta project within the group was one of those flagship initiative that directly seek to ensure environmental sustainability.
She also highlighted that in a playing part in controlling this ecological challenge that is salvinia, the company had collaborated with the department of water and sanitation in the setting up of salvinia weevils breeding ponds in the camps.
The major setback in control of the weed, according to her, is that the weevils’ reproduction drops dramatically when temperatures are lower, only to pick up when it becomes warmer. The winter season therefore presents a significant resurgence of infestations due this setback.
Breeding ponds, with regulated temperatures to ensure healthy weevil population even in winter would be the solution, she said. This would allow weevils abundance even when its winter.
Monnamorwa then pledged her support for the use of both the biological control and physical control methods to complement each other for efficacy. Physical control would allow for salvinia to be handpicked from the water bodies and be disposed in areas where it would not survive or regerminate
Key to effective control, and besides the methods used, Monnamorwa is of the of the view that its collaboration between the department, the tourism industry and various stakeholders. The long awaited memorandum of understanding with the industry would be an efficacious tool on the management and control of the weed to save the water systems.
The department of Water Affairs and Sanitation – North West regional manager, Keodumetse Kehitile
Itseng Kgosidialwa, water engineer with the department of water and sanitation who is responsible for the monitoring of salvinia molesta in the Okavango Delta in a recent interview cited the lack of resources, mainly transport as a hindrance in their bid to effectively monitor and control the weed.
He has noted that they are currently working on a Memorandum of Understanding (MoU) which when finalised will intensify their collaboration with tourism operators in the delta on control of the weed.
“We have once done activities which were dealing with the control measures and engaged some operators for assistance but because of financial constraints we could not further engage our communities to assist in that regard.”
Meanwhile, he buttressed that the current method is effective noting that they do comparison before and after applying releasing the weevils, adding that the results are visible and impressive.
Although the infestation of these weed is identified in both the down and upper streams of the Okavango Delta, Kgosidialwa indicated that they are more focused on the downstream which has the most concentrated infestations.
The department of Water Affairs and Sanitation – North West regional manager, Keodumetse Kehitile has also assured previously assured, while acknowledging the spike in infestations, that the control method they use is effective.
He also highlighted its shortcomings like Monnamorwa that the weevils’ reproductive metabolism goes down during winter season and only picks up again in summer which is their most vibrant times.
“Biological control by its nature does not completely eliminate the weed because to sustain the existence of these weevils there has to always be some patches of salvinia which they must feed on. So it’s not complete elimination,” Kehitile also clarified.
He acknowledged that there are also alternative methods- being the physical and chemical ones which they have applied before but because of certain challenges they had to stop using them. The physical method is whereby the weed is removed by handpicking while the chemical one involves the spreading of herbicides into the river where there is infestation.
