African boxthorn

African boxthorn (Lycium ferocissimum Miers) is a densely branched perennial shrub that can grow 5 m high and 5 m across. It is native to South Africa where it is widely distributed in a variety of climatic conditions. In the 19th century, boxthorn was introduced in Australia and was advocated as a good hedgerow and windbreak plant. Since then, the plant has rapidly spread across the continent in a wide range of landscapes and climates; thus in 1925, the South Australian government declared L. ferocissimum as a noxious weed. As the plant continued to spread, other regions of Australia (except West Australia) have declared it as a weed. Boxthorn is difficult to control due to its establishment as dense, impenetrable and thorny thickets, present across a broad range of landscapes and its continued spread. Long-term effective control of L. ferocissimum requires a combination of treatments over many years due to the capacity of the species to regenerate from the rootstock, stems and seed. Mechanical and chemical control methods have had low success in suppressing the plant due to a persistent seed bank, strong re-colonisation capacity, and expense. Current physical and chemical control measures are considered to be quite destructive and therefore unsuitable in culturally valuable and ecologically sensitive areas, as this requires extensive planning and is unsustainable over large areas.

Biological control offers promise as a control method as it is a safe, non-destructive, cost-effective and sustainable method of control. The relative taxonomic isolation of African Boxthorn to native Australian flora, together with its negative impact profile, makes the species a suitable target for biological control. The Indigenous Plants Invasive Elsewhere Programme is working in collaboration (assisting) with CSIRO Australia to develop a biological control programme for this species with the ultimate goal of reducing the negative consequences of this weed in Australia. Native range surveys for potential biological control agents are being conducted in South Africa by the staff and students of the Centre for Biological Control (CBC) at Rhodes University. These surveys are increasing the faunal and pathogen records of African boxthorn and its hybrids (or closely related species). The Indigenous Plants Invasive Elsewhere Programme also conducts lab and field host range studies which will enable the evaluation/forecasting of behaviour of agents when they are introduced in entirely new environments free of specialist enemies and exposed to potential new hosts and different selection pressures. Finally, there is taxonomic and phylogenetic confusion concerning the position of L. ferocissimum, so an essential aspect of the project is the collection of herbarium specimens and genetic samples, which are being used to resolve these taxonomic issues. 

Last Modified: Fri, 28 Sep 2018 14:55:45 SAST