Research on the Biological Control of Hakea sericea Over the Past Ten Years: Lessons Informing Future Management of the Species in the Western Cape Province, South Africa

Although Hakea sericea Schrad. & J.C. Wendl. (Proteaceae) remains a significant invasive species in parts of South Africa, efforts made to curtail its spread over the past decade have shown varying levels of success. Here, we describe progress-to-date with the insect agents and factors that have contributed to their success or failure. In particular we cover: (i) research on the ability of the seed-feeding weevil, Erytenna consputa Pascoe (Coleoptera: Curculionidae) to recolonise burnt areas after fire; (ii) the impacts and dispersal ability of the seed-feeding moth, Carposina autologa Meyrick (Lepidoptera: Carposinidae); (iii) the impacts and future prospects for the stem-boring beetle, Aphanasium australe (Boisduval) (Coleoptera: Cerambycidae); and (iv) the establishment discrepancy observed for the flowerbud-feeding weevil, Dicomada rufa Blackburn (Coleoptera: Curculionidae). In general, findings show: (i) E. consputa is able to quickly re-establish populations after fires; (ii) that C. autologa has a modest impact and disperses slowly; (iii) A. australe is performing relatively well in the field, with healthy localised populations in South Africa which should be left to increase before harvesting and redistribution of the beetle commences; (iv) climate mismatch between native and introduced ranges is a problem for D. rufa, along with other possible causes for establishment discrepancies which are still under investigation. As a result of these findings, we provide suggestions for possible management plans for some of the agents, so as to maximize resources and increase the overall impact of the H. sericea biological control programme in South Africa.