Conservation Ecology
Welcome to Stellenbosch University
Conservation Ecolog​​​y & Entomology​ 

News​

 

 

Biological pest control measures: researchers now know how to transport tiny nematodes to farms http://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=8141Biological pest control measures: researchers now know how to transport tiny nematodes to farms Engela Duvenage<p>​For the past 18 years, researchers at Stellenbosch University (SU) have studied a selection of nematodes found naturally in South African soils. In the process they have identified quite a few such roundworm species that could be used to biologically control agricultural pests. A recent MSc Entomology graduate, Ms Abongile Nxitywa, has now solved one of the conundrums that have so far stumped the SU research team's efforts to roll out this natural pest control method for use on local farms: how to store and transport them live, and <em>en masse.</em></p><p>Her finding now opens the door for opportunities to commercialise the use of nematodes within the South African agricultural setting, as a substitute for chemical pesticides. Similar commercial endeavours are already underway in America.</p><p>“Because of the biosecurity risks involved, it is always better to use local species in pest control," highlights Prof Antoinette Malan, project leader of the Nematode Laboratory in the Department of Conservation Ecology and Entomology. </p><p>According to calculations, about 2,5 million nematodes are needed if one is to spray one hectare of orchards against pests such as codling moth, false codling moth, weevils and mealybugs. To do this regularly on a reliable commercial scale will require quite an operation to ensure a steady supply. </p><p>“It sounds easy to do, but bear in mind that all the beneficial species we have so far identified are smaller than one millimetre in size," explains Prof Malan, who has been focusing on nematodes since the early 2000s.</p><p>In fact, the species are so small that without the benefit of a microscope, one needs seriously good eyesight to see one move.</p><p>They are also not as abundant as one might think. Prof Malan says that over the years only 5% of the soil samples that she has collected from all over the country have contained nematodes. These then had to be tested to pinpoint the ones that work against local agricultural pests such as codling moth and false codling moth. </p><p>Nematodes are parasitic in nature. They attach to insects, and penetrate their bodies through an opening, such as a pore. Once inside, they release a bacterium which then kills the insect.</p><p>Ms Nxitywa, who hails from Mthatha, says she had agricultural science as a school subject, and it was therefore an easy choice to pursue the topic further as a student. She was first introduced to nematodes during her third year of studies, but at that stage the topic did not grab her. In her fourth year as a BScAgric student, she worked with Prof Malan on a related project.</p><p>“Prof Malan taught me to love them," she now enthuses.</p><p>Ms Nxitywa graduated with a BScAgric in Agronomy and Plant Pathology in 2018, and in 2019 worked for six months as a research assistant in Prof Malan's Nematology Laboratory.</p><p>“During this time, she showed an extraordinary ability to master such high-technologically advanced techniques as the molecular identification of nematodes and the successful <em>in vitro</em> liquid mass culture of nematodes," says a very proud Prof Malan. “Her adeptness with such techniques earned her a departmental bursary, and she which led to her promptly switching from being a research assistant to becoming a postgraduate student."</p><p>For her MSc project, Ms Nxitywa tackled the issue of how to formulate and optimise the long-term storage and use of parasitic nematodes that prey on insects. </p><p>“Their commercialisation as biological control agents are hampered by their short shelf life. I wanted to find a preservation method that can improve their storage, without negatively affecting their infectivity against target pest insects," she explains. </p><p>It was easier said than done, because amid the first Covid-19 lockdown period Ms Nxitywa was one of only a few students initially allowed back on campus, and the only one from her lab permitted in the JS Marais Building where the research facilities of the Department of Conservation Ecology and Entomology are situated. </p><p>Ms Nxitywa needed large quantities of two South African nematode species, <em>Steinernema jeffreyense</em> and <em>Steinernema yirgalemense</em>, to test her formulations. The Covid restrictions meant that she did not have the benefit of a research assistant or a fellow student to help her in culturing these roundworms in large quantities. </p><p>“She did not to let this setback hold her back, and promptly started to culture her own nematodes," Prof Malan tells the story. “Her time as a research assistant came in handy, because she used a technique she had previously learnt from Murray Dunn, a PhD student who is using bioreactors to mass produce nematodes."</p><p>In the process, Ms Nxitywa was able to raise about more than enough nematodes for her experiments. </p><p>“There was a lot of trial and error," Ms Nxitywa admits.</p><p>At long last she could embark on her actual research endeavour: to find a way to keep and transport the tiny organisms for distribution and use on farms. </p><p>She tested various mediums, and finally settled on three. One looks like translucent play dough, while another looks like course sea sand is called diatomaceous earth (also known as kieselgur). Nematodes can be stored a high concentration of 700 000 nematodes per grams of diatomaceous earth. Alga-based beads the size of ones that one would typically find on a bracelet were also tested. Ms Nxitywa was able trap up to 5000 nematodes in one such bead. </p><p>“Diatomaceous earth formulation would work well for commercial application as it dissolved in water, while in the case of beads, they can act as a slow release of nematodes in undercover production such as blueberries," says Prof Malan.</p><p>Ms Mxitywa tested the ability of the various formulations to preserve nematodes under different temperatures and found that 14 degrees Celsius is optimal.</p><p>“You can keep them at room temperature, but for only about 4 weeks until a type of fungi starts growing on the medium," she explains.</p><p>It was a great moment when after months of trial and error she realised that she was able to keep the nematodes alive for at least 8 weeks under optimal conditions.  </p><p>In recognition of her work, Ms Nxitywa received her MScAgric degree in Entomology <em>cum laude </em>during the March graduation ceremony. </p><p>One of the four papers she has subsequently prepared as part of her thesis have so far been accepted and will appear in due course in the South African Journal of Enology and Viticulture.</p><p>Prof Malan says that ideally it would be great to get a local commercial partner involved to take their research findings further into the commercial space. She however realises that this would come at a great investment cost. </p><p>More research in large-scale field trials is still needed to test the effectiveness and persistence of the formulations' use under field conditions. ​<br></p><p><br><br></p>
Life on Earthhttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6596Life on EarthG.Thomas<p>​<span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;">Life on earth depends on the complex interactions between microbes such as fungi and other kingdoms, living or dead</span><br><br></p>
Insects are importanthttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6594Insects are importantG.Thomas<p>​<span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;">Insects are important in the function of ecosystems as they are critical in pollination, nutrient cycling and pest control. These are the creatures that run our world</span><br></p>
The future of our planethttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6595The future of our planetG.Thomas<p>The future of our planet and the conservation of species and systems are in the hands of our youth. Research, education and engagement are just some of the tools that we use to aid our cause<br></p>
The Proteaceae are flagship species for conservation, and an integral part of our rich endemic Cape florahttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6559The Proteaceae are flagship species for conservation, and an integral part of our rich endemic Cape floraG.Thomas<p>​​​<span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;">​The Proteaceae<span class="Apple-converted-space"> </span></span><span style="font-family:calibri, sans-serif;font-size:14.6667px;color:#1f497d;">are flagship species for conservation,<span class="Apple-converted-space"> </span></span><span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;">and an integral part of our rich endemic Cape flora</span>​<br><br></p>
​​Clearing of invasive plants benefits our natural freshwater systemshttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6561​​Clearing of invasive plants benefits our natural freshwater systemsG.Thomas<p>​<span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;">​Clearing of invasive plants benefit</span><span style="font-family:calibri, sans-serif;font-size:14.6667px;color:#1f497d;">s</span><span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;"><span class="Apple-converted-space"> </span>our natural freshwater systems</span><br></p>
Conservation of megaherbivores in natural systems benefits all trophic levelshttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6562Conservation of megaherbivores in natural systems benefits all trophic levelsG.Thomas<p>​<span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;">​​Conservation of megaherbivores in natural systems benefit</span><span style="font-family:calibri, sans-serif;font-size:14.6667px;color:#1f497d;">s</span><span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;"><span class="Apple-converted-space"> </span>all trophic levels</span>​<br></p>
Small mammals form an important link between primary producers and mesopredators, and are indicators of habitahttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6563Small mammals form an important link between primary producers and mesopredators, and are indicators of habitaG.Thomas<p>​<span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;">​​​​Small mammals form an important link between primary produce</span><span style="font-family:calibri, sans-serif;font-size:14.6667px;color:#1f497d;">r</span><span style="color:#000000;font-family:calibri, sans-serif;font-size:14.6667px;">s and mesopredators</span><span style="font-family:calibri, sans-serif;font-size:14.6667px;color:#1f497d;">, and are indicators of habitat health</span><br></p>
Linda Luvuno: caring for grasslandshttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6322Linda Luvuno: caring for grasslandsCarolyn Cramer<p style="text-align:justify;">​​ “I always admired Mother Theresa's compassion and commitment to helping people," says Linda Luvuno, who received her PhD in Conservation Ecology during the Faculty of AgriSciences' graduation ceremony on 2 April. “I dreamed of becoming a nurse so that I could do just that."<br></p><p style="text-align:justify;">Growing up in eMpophomeni in Howick, Luvuno loved the grasslands. When she began to realise the impact of alien invasive species, it saddened her deeply.<br></p><p style="text-align:justify;">“I grew up in a rural township where grass is pretty much life. We use it for all manner of things and so the impacts of woody encroachment could be devastating to communities. I realised that I didn't need to be a nurse to practically help people. In fact, contributing to a better society could take many forms and I see my research as one such way of doing so."</p><p style="text-align:justify;">Luvuno's research was a collaboration between the Centre for Complex Systems in Transition and the Department of Conservation Ecology & Entomology, both at the University of Stellenbosch.</p><p style="text-align:justify;"> </p><p style="text-align:justify;">In her thesis, titled <em>Understanding social-ecological regime shifts: the case of woody encroachment in South Africa</em> Luvuno builds on the ecological literature on encroachment to present a broader social-ecological understanding of woody encroachment. Humanity has been very successful in modifying the planet to meet the demands of a rapidly growing human population. As human activities have grown in magnitude, they have become increasingly interlinked with ecosystem dynamics, creating social-ecological systems. Increased human impacts on ecosystems are also leading to an increased occurrence of regime shifts: large, persistent changes in the structure and function of ecosystems and social-ecological systems that often have substantive impacts on the suite of ecosystem services provided by these systems, and on the well-being of people who live in them. As global changes accelerate, better understanding the drivers, impacts and risks of regime shifts has become a key need.</p><p style="text-align:justify;"> </p><p style="text-align:justify;">This knowledge has important implications for the formulation of management strategies that aim to either maintain existing desirable regimes, restore previous regimes where a regime shift has occurred, or facilitate transformation to new regimes in the novel planetary conditions we face.</p><p style="text-align:justify;"> </p><p style="text-align:justify;">A prevalent regime shift in savannas worldwide, and certainly in Luvuno's home province of KwaZulu Natal, is woody encroachment. Woody encroachment is a shift from a grassy savanna to a persistently woody savanna, and has direct implications for a variety of ecosystem services such as livestock grazing, and people's livelihoods that depend on these services. Much of the historical work on woody encroachment has focused on the direct drivers of the process, such as the role of fire or grazing in inhibiting or promoting encroachment. However, less is understood about how underlying social processes may impact these drivers, how ecological changes may feedback to affect some of these underlying social processes, how to monitor woody encroachment as a regime shift and how encroachment impacts ecosystem services and human well-being.</p><p style="text-align:justify;"> </p><p style="text-align:justify;">“A real highlight of my research was spending time back in Zululand interviewing community members and game reserve staff about woody encroachment. Living in the Cape for so many years, I'd forgotten how friendly Zulu people are and how much I missed grass! It seems so silly but the landscapes we grow up in can be attached to our identity. Being there was cathartic."</p><p style="text-align:justify;"> </p><p style="text-align:justify;">Linda hopes that her research will inform policy and management practices, emphasising the importance of understanding the social and ecological interactions that underlie woody encroachment.</p><p style="text-align:justify;"> </p><p style="text-align:justify;">​ <br></p><p><br></p>
Matie researcher wants more cat fleashttp://www.sun.ac.za/english/Lists/news/DispForm.aspx?ID=6302Matie researcher wants more cat fleasEngela Duvenage<p>​Most people visit their local animal welfare association only when they want to adopt a new kitten or puppy. Not Dr Luther van der Mescht. He goes to visit in search of fleas. To be precise, cat fleas. He is working on a comprehensive study of the different species found on South African dogs and cats.<br></p><p>Worldwide, cat fleas (<em>Ctenocephalides felis felis</em>) are the most commonly found fleas plaguing pets. Despite their name, these little insects also occur on dogs. Animals covered with these fleas often suffer from tapeworms over time, and can become quite emaciated in the process.<br></p><p>Dr van der Mescht hopes to be able to determine which species are all found in South Africa. He will be using microscope and genetic techniques to study the fleas that he collects. Such information can ultimately be valuable when trying to ensure that the right types of flea repellents are used in different regions. </p><p>"It is very difficult to identify with the naked eye species which fleas are all members of the <em>Ctenocephalides felis</em>-complex, and therefore we do not really know which species of cat fleas are found on South African dogs or cats," explains Dr van der Mescht. "The previous thorough survey on the topic was done in the 1970s."</p><p>His research project is funded by the Claude Leon Foundation.</p><p>Dr Van der Mescht works closely with parasitologist Prof Sonja Matthee of the SU Department of Conservation Ecology and Entomology, who concentrates on parasites such as fleas and ticks, and evolutionary biologist Prof Conrad Matthee from the SU Department of Plant and Zoology.</p><p>According to Dr van der Mescht, 20 animal welfare organizations and private veterinarians across the country are already involved in his studies. They are helping him to collect enough fleas from a diversity of regions so that he can identify and genetically study them.</p><p>Members of the public who are interested in helping his research can send flea samples collected from their cats and dogs to Dr van der Mescht until the end of April. This is when the typical summer flea season ends. It is best to store dead insects in a small container of ethanol.</p><p> For inquiries about how to do so, contact Dr van der Mescht at luthervdm@sun.ac.za.</p><p>​<br> <strong><span lang="EN-ZA" style="line-height:107%;font-family:calibri,sans-serif;font-size:13pt;">Background: Dr Luther van der Mescht<br> </span></strong><span lang="EN-ZA" style="line-height:107%;font-family:calibri,sans-serif;font-size:11pt;">• He obtained his doctorate in conservation ecology in 2015 at Stellenbosch University after researching the factors that determine the variety and distribution patterns of fleas on mice across South Africa.<br> • From September 2016 to September 2018, he did postdoctoral research at the Ben-Gurion University of the Negev in Israel. He worked under one of the world's leading flea scientists, Professor Boris Krasnov.<br> • Currently, he is a postdoctoral fellow at Stellenbosch University, and focuses on expanding and updating information on the diversity, evolution and habitats of different South African fleas.<br> • He matriculated in 2004 at Punt High School in Mossel Bay.<br> <br> </span>​<br></p><p><br> </p>