A Review of Research and Developments with Insect Agents Used for Biological Control of Australian Acacia Species (Caesalpinioideae) in South Africa

There are 14 species of Australian Acacia now known to be invasive in South Africa, ten of which are under some form of biological control (biocontrol). The biocontrol agents introduced against this group include a fungal pathogen, Uromycladium morrisii Doungsa-ard, McTaggart, Geering & R.G. Shivas (Pucciniales: Raveneliaceae) for Acacia saligna (Labill.) H.L.Wendl., and ten insect species, including two bud-galling wasps, five seed-feeding weevils and three flower-galling fly species, all of which supress reproductive output of their hosts. There are also two native fungal pathogens that have become associated with the introduced acacias, and which have been developed for potential mycoherbicide use. Screening and importation of new agents has seen limited activity in the ten-year period reviewed here (i.e., 2011–2020). Most attention has been focussed on efforts to evaluate the effectiveness of the established agents and, importantly, to gain an understanding of the role of seeds in the population dynamics of the host plants.