Biological control of Australian Acacia species and Paraserianthes lophantha (Willd.) Nielsen (Mimosaceae) in South Africa

In total, ten agent species have been released in South Africa for the biological control of ten invasive Australian Acacia species and Paraserianthes lophantha (Willd.) Nielsen (Mimosaceae). Besides a single fungal pathogen species which affects both reproductive and vegetative growth of its host plant, Acacia saligna (Labill.) H.L.Wendl., there are nine herbivorous insect species which predominantly suppress the reproductive output of their host plants. These include five seed-feeding weevil species, two flower-galling fly species and two bud-galling wasp species. An indigenous basidiomycete fungus, which causes die-back disease of Acacia cyclops A.Cunn. ex G.Don, has also been investigated. During the last ten years, considerable effort has been directed at searching for new agents in Australia and in collecting additional material to bolster populations of recently-established agents in South Africa. Concurrently, ongoing evaluation studies in South Africa have measured the dynamics of the introduced agents as well as their impact on the vigour and fecundity of their host plants and the extent to which their damage is reducing the density, distribution and invasiveness of the Acacia species. Progress with all of these projects is reviewed.