It was a double celebration for Caitlin Gevers who was capped at the University of Pretoria’s Spring Graduation on 1 September and presented her Prestige Seminar “Changes in genetic diversity of Leptocybe invasa populations in South Africa and its impact on pest management” on 2 September, marking the successful completion of her PhD.

Caitlin’s PhD was completed under the supervision of Prof. Brett Hurley, Prof. Bernard Slippers, and Dr Gudrun Dittrich-Schröder. Prof. Irene Barnes was the Internal Examiner for her thesis while the external examiners, Dr Andy Howe (University of the Sunshine Coast, Australia) and Dr Steve Pawson (University of Canterbury, New Zealand) both joined online for Caitlin’s Prestige Seminar.

Prof. Brett Hurley was fulsome in his praise for Caitlin’s resilience in pushing through to complete an excellent piece of work despite numerous challenges. He said that Caitlin was the right person for the job and persisted despite having to work with tiny insects. He also commended her for being active in fieldtrips and at the FABI Biocontrol and Insect Rearing Facility.

FABI Director Prof. Bernard Slippers also commended Caitlin on her hard work saying that her PhD showed a deep understanding of Leptocybe, that it was a big contribution to the study of invasion biology and that she had mastered a wide range of skills during her PhD which included a massive sampling effort of over 100,000 samples and successfully establishing colonies of minute wasps!

Leptocybe invasa is an important and devastating pest of Eucalyptus in South Africa. The importance of her study can be gauged by the fact that several collaborators from the forestry industry also joined the meeting online.

Caitlin’s PhD investigated the genetic diversity of insect pests at the subspecies level and its importance in managing invasive agricultural and forestry pests. In South Africa, two genetically distinct Leptocybe lineages (A and B), which are likely cryptic species, exist simultaneously. Molecular and morphological analyses indicated that Lineage A was already widespread at the start of this study, while Lineage B originally showed a limited distribution but has since spread to all forestry regions. Her study also shed light on the host preference of the two linages and distribution of biological control agents and parasitoids

These findings can inform breeding programs aimed to develop resistant host genotypes and biological control programmes that consider sub-species diversity of the target insect. This thesis made an important contribution to the understanding of genetic diversity of invasive insect pests and the consequences of that diversity to management approaches.