Objects
Zimmermann, Helmuth G. Rhodes University; 1982. The ecology and control of Opuntia Aurantiaca in South Africa in relation to the cochineal insect, Dactylopius Austrinus.
Klein, Hildegard, Hill, Martin P, Zachariades, Costas, Zimmermann, Helmuth G. Regulation and risk assessment for importations and releases of biological control agents against invasive alien plants in South Africa. 2011.
Mafokoane, L D, Zimmermann, Helmuth G, Hill, Martin P. Development of Cactoblastis cactorum (Berg)(Lepidoptera: pyralidae) on six north American Opuntia species. 2007.
Paterson, Iain D, Hoffmann, John H, Klein, Hildegard, Mathenge, C W, Neser, Stephan, Zimmermann, Helmuth G. Biological control of cactaceae in South Africa. 2011.
Robertson, Mark P, Villet, Martin H, Fairbanks, Dean H K, Henderson, L, Higgins, Simon I, Hoffmann, John H, Le Maitre, David C, Palmer, Anthony R, Riggs, I, Shackleton, Charlie M, Zimmermann, Helmuth G. A proposed prioritization system for the management of invasive alien plants in South Africa. 2003.
Paterson, Iain D, Manheimmer, C A, Zimmermann, Helmuth G. Taylor and Francis Online; 2018. Prospects for biological control of cactus weeds in Namibia.
Hill, Martin P, Moran, V Clifford, Hoffmann, John H, Neser, Stefan, Zimmermann, Helmuth G, Simelane, David O, Klein, Hildegard, Zachariades, Costas, Wood, Alan R, Byrne, Marcus J, Paterson, Iain D, Martin, Grant D, Coetzee, Julie A. Springer, Cham; 2020. More than a century of biological control against invasive alien plants in South Africa: a synoptic view of what has been accomplished.