Mr Harm Barten
Zoology and Entomology
As an entomologist my interests involve insect diversity and biological control. This began when I started collecting insects at the age of 9 while visiting my grandfather in South Africa. Naturally following on this, I did my BSc and MSc at Wageningen University in The Netherlands where I studied Biology with a specialization in biological control of insects. During the bachelor I took part in the minor Ecology and Biological Control of Insects, and for my masters I did an artificial selection experiment on geotaxis behavior of the two-spot ladybird beetle, a natural enemy of aphids. Furthermore, I did an internship at the North West University in Potchefstroom, where I studied the effect of host size on the development of a parasitoid of stemborers in maize.
At the moment I am doing my PhD in entomology in the Forestry & Agricultural Biotechnology Institute (FABI) at the University of Pretoria. I am working on biological control of the Eucalyptus Snout Beetle Gonipterus sp. n. 2, a major pest in South African Eucalyptus plantations. To control this pest, the egg parasitoid Anaphes nitens was imported from the native range in Australia and released in South Africa in 1926. Although this introduction is generally seen as a main example of successful classical biological control, the pest remains of importance for the forestry industry today. From a literature review we found that several environmental factors are involved in (un)successful biocontrol of Gonipterus sp. n. 2, such as climate change and variation in host trees. A lack of genetic diversity of A. nitens, due to a bottleneck at introduction, has been hypothesized to impair its ability to cope with the variable environment, sometimes resulting in the breakdown of biocontrol.
Because of this, in 2022 a new A. nitens population was imported from Boonah, Queensland, from an area better climatically matched to the main Eucalyptus growing areas in South Africa. Before release, I compared several fitness characteristics of the two populations and the crosses between them, to ensure reproductive compatibility. No signs of reproductive barriers were found, and the new Australian population was released near Ixopo in Kwa-Zulu Natal.
Now I am studying the population genetics of A. nitens in South Africa and comparing it to samples from the native range in Australia as well as specimens from Brazil and Portugal, where the parasitoid was also released for biological control. I designed a set of 15 microsatellite markers and genotyped around 950 parasitoids. The analyses are currently underway, and they will increase our understanding of population structure and genetic differentiation in the A. nitens populations.
Some separation between the Australian and South African A. nitens populations was observed, and by using pre-release samples, unique Australian microsatellite alleles could be determined. Those unique alleles will now be used to track the establishment and spread of the newly imported A. nitens population from Boonah, by genotyping a series of post-release samples. If we find the Australian A. nitens alleles back in the South African population, the abundance and distribution will give us insight into potential fitness benefits of this new population and the possible benefits for biocontrol.
Besides my PhD, I am involved in identifying insect samples that we receive through the TPCP Diagnostic Clinic. This involves managing incoming specimens and preserving them appropriately, as well as performing morphological identifications. For insects that we cannot reliably identify using morphology, we use DNA barcoding to get to a species name.
Twenty four FABIans attended and presented at the recent 23rd Congress of the Entomological Society of Southern Africa.
The TPCP held its 34th Annual Meeting at the Future Africa conference centre, where staff, postdoctoral Fellows and students present their work to industry and government stakeholders as feedback on the work conducted in the past year.
A tiny egg parasitoid, Anaphes nitens, was released in the KwaZulu-Natal Midlands for the control of the eucalypt snout beetle.
Despite travel restrictions due to the COVID-19 pandemic, a shipment of Anaphes nitens collected in Queensland, Australia was received by the FABI biocontrol facility at the University of Pretoria’s experimental farm last week.