Author
Grant Martin
g.martin@ru.ac.za
Centre for Biological Control, Department of Zoology and Entomology, Rhodes University P.O. Box 94, Grahamstown 6140, South Africa
Afromontane Research Unit and Department of Plant Science, University of the Free State, QwaQwa, South Africa
Coauthors
Kim Canavan, Centre for Biological Control, Department of Zoology and Entomology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa, and Afromontane Research Unit and Department of Plant Science, University of the Free State, QwaQwa, South Africa
Gerald Chikowore, Centre for Biological Control, Department of Zoology and Entomology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa
Phillip Weyl, CABI, Delémont, Switzerland
Abstract
Invasive alien trees present unique challenges and opportunities for biological control due to their long lifespans, large stature, ecological impacts, and societal value. Despite well-documented ecological harm, invasive trees remain underrepresented in global biological control programs. Yet, some of the most successful outcomes in weed biocontrol involve invasive trees such as the >90% reduction in Tamarix spp. density in North America following the release of Diorhabda carinulata and the decline of Australian Acacias in South Africa. Unfortunately, there has been a concerning decline in new tree biocontrol programs, despite their proven efficacy. For instance, South Africa despite being the most severely affected country by tree invasions globally and having a successful history of tree biological control dating back to the 1970s has experienced a 70% reduction in programmes targeting invasive alien trees over the past decade. Several challenges contribute to this decline including securing long-term funding usually required for testing trees, difficulties of working with trees in quarantine amid tightening regulations, and unresolved conflicts of interest among stakeholders. By analysing past successes, limitations, and emerging trends, we assess whether tree biocontrol remains a worthwhile pursuit or risks becoming obsolete due to regulatory and socio-political constraints. To overcome these barriers, we advocate for innovative approaches to accelerate biocontrol programmes.
keywords
Invasive trees
Biological control
Declining programmes
Highlights
Invasive trees cause major harm but are hard to control
Tree biocontrol programs declining despite success
Innovative approaches needed to revive tree biocontrol