Assessing the status of biological control as a management tool for suppression of invasive alien plants in South Africa

Abstract

Background: Biological control of invasive alien plants (IAPs) using introduced natural enemies contributes significantly to sustained, cost-effective management of natural resources in South Africa. The status of, and prospects for, biological control is therefore integral to National Status Reports (NSRs) on Biological Invasions, the first of which is due in 2017. Objectives: Our aim was to evaluate the status of, and prospects for, biological control of IAPs in South Africa. We discuss expansion of biological control and suggest indicators to be used in the upcoming NSR to assess sufficient growth. Method: We used published literature, unpublished work and personal communication to assess the status of biological control of IAPs. We propose indicators based on the targets for biological control that were proposed in the 2014 ‘National Strategy for dealing with biological invasions in South Africa’. To prioritise targets for future efforts, we used published lists of damaging IAPs and assessed the prospects for their biological control. Recommendations for using biological control as a management tool were made after discussion among the authors and with colleagues. Results: Significant control of several Cactaceae, Australian Acacia species and floating aquatic plants, and many other IAPs has been achieved in South Africa since 1913. Recently, biological control has benefited from improved international collaboration, a streamlined application process for the release of new biological control agents (resulting in the approval of 19 agents against 13 IAP species since 2013), and increased funding and capacity. There is still a need to improve implementation and to better integrate biological control with other control methods. In order to maximise benefits from biological control, increased investment is required, particularly in implementation and post-release evaluation, and in targeting new IAPs. Proposed targets for growth between 2017 and 2020 include an increase in financial investment in research by 29%, implementation by 28% and mass-rearing by 68%. Research capacity should increase by 29%, implementation capacity by 63% and mass-rearing capacity by 61%. New research projects should be initiated on 12 new IAP targets, while post-release monitoring efforts should be expanded to another 31 IAPs. Conclusion: Biological control of IAPs has contributed substantially to their management in South Africa, and continues to do so. Further investment in targeted aspects of IAP biological control will increase this contribution.

Biotic Interactions as Mediators of Biological Invasions: Insights from South Africa

“…As posited by the ERH, the liberation from highly specialised parasitic interactions (such as herbivores or pathogens) will aid establishment success. More than a century of biological control of invasive plants in South Africa provides strong support for the role of enemy release in plant invasiveness (Zachariades et al 2017; also see Hill et al 2020, Chap. 19), although the high levels of control observed can equally be explained by the biological control agents having been released from their natural enemies.…”

Ghosts from the past: even comprehensive sampling of the native range may not be enough to unravel the introduction history of invasive species—the case of Acacia dealbata invasions in South Africa

“…Invasive Australian acacias (genus Acacia s.s. formerly Acacia subgenus Phyllodineae, family Fabaceae) are major contributors to the reduction of this critical ecosystem service (Le Maitre et al., ). While many types of control measures are being implemented to reduce the extent and impacts of invasive plants in South Africa, including biological control (Zachariades et al., ), substantial challenges remain (Richardson and Kluge, ; van Wilgen and Wannenburgh, ).…”

Analysing the Risks Posed by Biological Invasions to South Africa

“…Permit applications for the release of biological control agents, including an estimate of the likelihood and consequences of non-target effects and an assessment on the potential benefits of the introduction, are compiled by a dedicated team of scientists and submitted to the decision making body (in this case chaired by DALRRD). The applications including the risk assessments are then reviewed by an independent panel of experts similar to ASRARP, namely the National Biological Control Release Application Review Committee (Zachariades et al 2017), and sent for review to international experts. The record of safety is enviable.…”