John Hoffmann leads a team of entomologists working on the use of herbivorous insects for biological control of invasive alien plants (IAPs). The team includes Fiona Impson, Carein Kleinjan and Cliff Moran. Their particular interest is in determining how effective introduced insects are in reducing the density, abundance and rate of spread of IAPs. The UCT team collaborates closely with entomologists and plant pathologists from 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. The UCT group sets up monitoring programmes to quantify how much damage is being caused by the agents on the plants and whether this is sufficient to curb the invasiveness and abundance of the IAP in question.
Most of the recent efforts of the UCT group have focussed on invasive Australian Acacia species, but insects on other IAPs, including cacti, pine trees, mesquite (prosopis), hakeas and sesbania, are also under investigation. The work has shown that several of the introduced biological control agents have had a major impact on some IAPs, 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.
van Wilgen B.W., Moran V. C. and Hoffmann J. H. 2013. Some perspectives on the risks and benefits of biological control of invasive alien plants in the management of natural ecosystems. (Environmental Management,
Impson F.A.C., Post J. and Hoffmann J.H. 2013. Impact of the flower-galling midge, Dasineura rubiformis Kolesik, on the growth of its host plant, Acacia mearnsii De Wild, in South Africa. South African Journal of Botany 87: 118-121.
Kleinjan C.A.and Hoffmann J.H. 2013. Advances in clarifying the phylogenetic relationships of acacias: relevance for biological control. Acta Oecologia 48: 21-29.
Haiden S.A., Hoffmann J.H. and Cramer M.D. 2012. Benefits of photosynthesis for insects in galls. Oecologia 170: 987-997.
Moran V.C. and Hoffmann J.H. 2012. Conservation of the fynbos biome in the Cape Floral Region: the role of biological control in the management of invasive alien trees. Biocontrol 57: 139-149.
Marchante H., Freitas H. and Hoffmann J.H. 2011. Post-clearing recovery of coastal dunes invaded by Acacia longifolia: is duration of invasion relevant for management success? Journal of Applied Ecology 48:1295-1304.
Paterson I.D., Hoffmann J.H.,Klein H., Mathenge C.W., Neser S. and Zimmermann H.G. 2011. Biological control of Cactaceae in South Africa. African Entomology 19: 230-246.
Hoffmann J.H., Moran V.C. and van Wilgen B.W. 2011. Prospects for biological control of invasive Pinus species (Pineaceae) in South Africa. African Entomology 19: 393-401.
Impson F.A.C., Kleinjan C.A., Hoffmann J.H., Post J.A. and Wood A. 2011. Biological control of Australian Acacia species and Paraserianthes lophantha (Mimosaceae), in South Africa. African Entomology 19: 186-207.
Zachariades C., Hoffmann J.H. and Roberts A. 2011. Biological control of mesquite (Prosopis species) (Fabaceae) in South Africa. African Entomology 19: 402-415.
Moran V.C., Hoffmann J.H. and Hill M.P. 2011. A context for the 2011 compilation of reviews on the biological control of invasive alien plants in South Africa. African Entomology 19: 177-185.
Wilson J.R.U., Gairifo C., Gibson M.R., Arianoutsou M., Bakar B.B., Baret S., Celesti-Grapow L., DiTomaso J.M., Dufour-Dror J-M., Kueffer C., Kull C.A., Hoffmann J.H., Impson F.A.C., Loope L.L., Marchante E., Marchante H, Moore J.L., Murphy D.J., Rinaudo A., Tassin J., Witt A., Zenni R.D. and Richardson D.M. 2011. Risk assessment, eradication, containment, and biological control: global efforts to manage Australian acacias before they become widespread invaders Diversity and Distributions 17: 1030-1046.
van Wilgen B.W., Dyer C., Hoffmann J.H., Ivey P., Le Maitre D.C., Moore J.L., Richardson D.M., Rouget M., Wannenburgh A. and Wilson J.R.U. 2011. National-scale strategic approaches for managing introduced plants: insights from Australian acacias in South Africa. Diversity and Distributions 17: 1060-1075.
Marchante H., Freitas H. and Hoffmann J.H. 2011. Assessing the suitability and safety of a well-known bud-galling wasp, Trichilogaster acaciaelongifoliae, for biological control of Acacia longifolia in Portugal. Biological Control 56: 193-201.
Marchante H., Freitas H. and Hoffmann J.H. 2011. The potential role of seed-banks in the recovery of dune ecosystems after removal of invasive plant species. Applied Vegetation Science 14: 107-119.
Kotze M.J., Jürgens A., Johnson S.D. and Hoffmann J.H. 2010. Volatiles associated with different flower stages and leaves of Acacia cyclops and their potential role as host attractants for Dasineura dielsi (Diptera: Cecidomyiidae). South African Journal of Botany 76: 701–709.
Marchante H., Freitas H. and Hoffmann J.H. 2010. Seed ecology of the invasive alien species Acacia longifolia (Fabaceae) in Portuguese dune ecosystems. American Journal of Botany 97: 1780–1790.
Van Driesche R.G., Carruthers R.I., Center T., Hoddle M.S., Hough-Goldstein J., Morin L., Smith L., Wagner D.L., Blossey B., Brancatini V., Casagrande R., Causton C.E., Coetzee J.A., Cuda J., Ding J., Fowler S.V., Frank J.H., Fuester R., Goolsby J., Grodowitz M., Heard T.A., Hill M.P., Hoffmann J.H., Huber J., Julien M., Kairo M.T.K., Kenis M., Mason P., Medal J., Messing R., Miller R., Moore A., Neuenschwander P., Newman R., Norambuena H., Palmer W.A., Pemberton R., Perez Panduro A., Pratt P.D., Rayamajhi M., Salom S., Sands D., Schooler S., Schwarzländer M., Sheppard A., Shaw R., Tipping P.W. and van Klinken R.D. 2010. Classical biological control for the protection of natural ecosystems. Biological Control 54: S2–S33.
Mathenge C.W., Holford P., Hoffmann J.H., Zimmermann H.G., Spooner-Hart R. and Beattie G.A.C. 2010. Determination of biotypes of Dactylopius tomentosus (Hemiptera: Dactylopiidae) and insights into the taxonomic relationships of their hosts, Cylindropuntia spp. Bulletin of Entomological Research 100: 347-358.
Mathenge C.W., Holford P., Hoffmann J.H., Zimmermann H.G., Spooner-Hart R. and Beattie G.A.C. 2010. Hybridization between Dactylopius tomentosus (Hemiptera: Dactylopiidae) biotypes and its effects on host specificity. Bulletin of Entomological Research 100: 331-338.
Post J.A., Kleinjan C.A., Hoffmann J.H. and Impson F.A.C. 2010. Biological control of Acacia cyclops in South Africa: the fundamental and realized host range of Dasineura dielsi (Diptera: Cecidomyiidae) Biological Control 53: 68-75.
Dorchin N., Hoffmann J.H., Stirk W.A., Novák O., Strnad M. and van Staden J. 2009. Sexually dimorphic gall structures correspond to differential phytohormone contents in male and female wasp larvae. Physiological Entomology 34: 359-369.
Mathenge C.W., Holford P., Hoffmann J.H., Spooner-Hart R., Beattie G.A.C. and Zimmermann H.G. 2009. Distinguishing suitable biotypes of Dactylopius tomentosus (Hemiptera: Dactylopiidae) for biological control of Cylindropuntia fulgida var. fulgida (Caryophyllales: Cactaceae) in South Africa. Bulletin of Entomological Research 99: 619-627.
Mathenge C.W., Holford P., Hoffmann J.H., Spooner-Hart R., Beattie G.A.C. and Zimmermann H.G. 2009. The Biology of Dactylopius tomentosus (Lamarck) (Hemiptera: Dactylopiidae). Bulletin of Entomological Research 99: 551-559.
LennoxC.L., Hoffmann J.H., Coutinho T.A. and Roques A. 2009. A threat of exacerbating the spread of pitch canker precludes further consideration of a cone weevil, Pissodes validirostris, for biological control of invasive pines in South Africa. Biological Control 50: 179-184.
Moseley C.T., Cramer M.D., Kleinjan C.A.and Hoffmann J.H. 2009. Is vegetative growth of Acacia cyclops impaired by carbon and nutrient costs of Dasineura dielsi-induced flower galls? Journal of Applied Ecology 46: 214-222.
Impson F.A.C., Kleinjan C.A., Hoffmann J.H. and Post J.A. 2008. Dasineura rubiformis (Diptera: Cecidomyiidae), a new biological control agent for Acacia mearnsii in South Africa. South African Journal of Science 104: 247-249.
Le Maitre D.C., Krug R.M., Hoffmann J.H., Gordon A.J. and Mgidi T.N. 2008. Hakea sericea: development of a model of the impacts of biological control on population dynamics and rates of spread of an invasive species. Ecological Modelling 212: 341-358.
Foxcroft L.C., Hoffmann J.H., Viljoen J.J. and Kotza J.J. 2007. Factors influencing the distribution of Cactoblastis cactorum, a biological control agent of Opuntia stricta, in Kruger National Park, South Africa. South African Journal of Botany 73: 113-117.
Foxcroft L.C., Hoffmann J.H., Viljoen J.J. and Kotza J.J. 2007. Environmental factors influencing the distribution of Opuntia stricta, an invasive alien plant in Kruger National Park, South Africa. South African Journal of Botany 73: 109-112.
Dorchin N., Cramer M.D. and Hoffmann, J.H. 2006. The carbon costs of wasp-induced galls on Acacia pycnantha. Ecology 87: 1781-1791.
Moran V.C., Hoffmann J.H. and Zimmermann H.G. 2005. Biological control of invasive alien plants in South Africa: necessity, circumspection, and success. Frontiers in Ecology and the Environment 3: 77-83.