Upcoming Talks

Diarise the date!

18 May 2019

Time: 5.30 pm for 6.00 pm

Venue: Nivenia Hall, Harold Porter Gardens

Enquiries: Rea Borcherds 028 272 9756


Prospects and Progress with Biological Control of Invasive Alien Trees in the Western Cape

By John Hoffmann, Department of Biological Sciences, University of Cape Town

Biological control, such as deliberately introduced insect and fungus species, has been used as one of the management options for reducing the invasiveness of several Australian tree species in South Africa. The results of some long-term studies will be presented which show that considerable progress has been made and that there are encouraging prospects going forward.

John Hoffmann is retired but continues part-time work on the use of herbivorous insects for biological control of invasive alien plants (IAPs). His particular interest is in determining how effective introduced insects are in reducing the density, abundance and rate of spread of IAPs.

He collaborates closely with other entomologists at UCT and at the Plant Protection Research Institute of the Agricultural Research Council, an organisation that carries most of the responsibility for finding new biocontrol agents, screening them to ensure they are safe and effective and releasing them on the target pest in South Africa. He is an associate of the Centre for Biological Control at Rhodes University.

His recent projects have focussed on invasive Australian Acacia species, but insects on other invasive plant species, including cacti, pine trees, mesquite (prosopis), hakeas and sesbania, have also been investigated. The work has shown that several of the introduced biological control agents have had a major impact on some invasive plants, which have become relatively scarce and unimportant as a result (e.g. cacti and Sesbania punicea), but often the effects of the insects are less obvious and require meticulous, long-term surveys to detect. The results of these investigations are showing that even quite subtle changes brought about by the biocontrol agents can translate into very real long-term benefits in terms of protecting natural habitats from the devastating effects of IAPs.