Dr Minette Karsten shares how she went from researching black rhinos to studying Mediterranean fruit flies and other pome- and stone-fruit pests. By Anna Mouton.

Hortgro has appointed Dr Minette Karsten to manage its crop-protection programme from 1 October 2024. She replaces Matthew Addison, who is retiring.

Karsten grew up in a smallholding outside Stellenbosch. She started her undergraduate training in the Faculty of Science at Stellenbosch University. “I wasn’t sure exactly what I wanted to do, but I knew I wanted a career in science,” she recalls.

She became interested in evolutionary genomics, especially the work of one of her lecturers, Prof. Bettine Jansen van Vuuren, and enrolled for an honours degree in zoology. The initial topic of her mini-dissertation was the endangered Karkloof Blue butterfly.

“It proved impossible to work on because we couldn’t find material,” says Karsten. So she switched to an animal that was easier to track down — the black rhino. “The idea was to look at the genetic health of different populations, to see whether the management strategy of moving animals between parks was working.”

This project allowed Karsten to learn various genetics techniques that were invaluable when she transitioned to researching insect pests for her master’s degree.

Focus on fruit flies

Karsten started her master’s degree in 2010 under the supervision of Profs Jansen van Vuuren and John Terblanche of the Centre for Invasion Biology at Stellenbosch University. The project harnessed the same skills as her black rhino research but for investigating population genetics of the Mediterranean fruit fly, Ceratitis capitata.

“As I was finishing that project, Bettine moved to the University of Johannesburg,” says Karsten. “So, for my PhD, I moved to the Department of Conservation Ecology and Entomology at Stellenbosch University for another fruit-fly project.”

From 2012, she worked on the indigenous Natal fruit fly, Ceratitis rosa, under the supervision of Profs Pia Addison and Terblanche. During her PhD, the Natal fruit fly was discovered to be two species, and one of these, Ceratitis quilicii, was named the Cape fruit fly.

“I still did some genetic work for my PhD,” says Karsten, “but I also started doing trap work and investigating other aspects of entomology.” This laid the foundation for her applied entomology and integrated pest management expertise.

Her PhD was also the start of her relationship with Hortgro, as she worked on a Hortgro-funded project. She says she has no regrets about leaving rhinos behind. “Once I moved to entomology, there was no looking back.”

Invasive and quarantine pests

“Bactrocera dorsalis was the next fruit fly I worked on as a postdoc,” says Karsten. Bactrocera dorsalis, the Oriental fruit fly, is an invasive pest in South Africa and is listed as a quarantine pest by the European Plant Protection Organisation.

Karsten’s research on Oriental fruit flies was followed by a project on population genetics of another quarantine pest, albeit a South African native, false codling moth. In 2018, she was awarded the Stellenbosch University Top 20 Award for her post-doctoral productivity in invasion biology, applied entomology, and molecular ecology.

From 2020 to 2021, she was a contract researcher at Stellenbosch University. She participated in the Horizon 2020 European Union-funded Fruit Flies In-silico project, an international collaboration of 21 institutions. Karsten’s contribution included studying fruit-fly physiology.

“Then Hortgro advertised for an applied entomologist in 2021,” she remembers. “I got the position, so I’ve been with Hortgro for three years.”

It has been an interesting three years with two new records of invasive pests in South Africa: the polyphagous shot-hole borer and yet another fruit fly, spotted wing drosophila, Drosophila suzukii. “Spotted wing drosophila brings me back to my fruit-fly roots,” jokes Karsten. “But I think it will be interesting — we still have many questions. For each new invasive, we must create new monitoring, surveillance, and control programmes, inform growers, and develop documentation and training.”

The Hortgro leadership programme

In addition to her scientific role, Karsten was in the first cohort participating in the Hortgro industry leadership programme, which aims to expose the next generation of industry leaders to industry structures and programmes.

“It was great to meet people from different spheres. Our research is mostly involved in preharvest aspects, so it was interesting to get a glimpse into the pack houses and markets — what happens to the fruit post-orchard,” she says.

The bigger-picture perspective she gained from the programme helps to inform her research approach. “As researchers, we often have ideas about what growers should do, but they have practical constraints and different ideas,” observes Karsten. “Networking and interacting with different people, and hearing how they address or approach specific questions, was one of the programme’s benefits.”

Karsten was part of a group of young leaders who visited Australia and New Zealand in late 2023 for a study tour. Although the details differ, she found that the crop-protection challenges facing their deciduous fruit industries align closely with the South African situation.

Going forward, she hopes that some insights gained from discussions with her peers will lead to research projects directly addressing growers’ needs. Meanwhile, Karsten points out that the crop protection programme is about more than the immediate threat posed by new invasives.

“We still have all of our other pests, and pests such as sucking insects that are emerging,” she says. “So, there are many additional challenges apart from the completely new, unknown pests.”