Reviving biological control efforts against invasive alien weeds in Zimbabwe
Gerald Chikowore, Martin Hill, Julie Coetzee, Kim Canavan,
Grace Hamah and Grant Martin
Centre for Biological Control (CBC), Rhodes University, South Africa
Invasive alien weeds pose a significant threat to Zimbabwe’s ecosystems, agriculture, and biodiversity, creating severe environmental and economic challenges. Zimbabwe has historically been a leader in Africa with regards to the implementation of biological control dating back to the 1960s. Unfortunately, progress has stalled due to limited resources, research gaps, and institutional challenges, with no new agents released since 2009. In response, the Centre for Biological Control (CBC), Rhodes University, South Africa, working with Zimbabwean authorities, has been actively revitalizing classical biocontrol programs in the country. Through this initiative, the CBC participated in a workshop co-hosted by the Food and Agriculture Organisation of the United Nations (FAO) to produce a national action plan for the management of invasive alien species in Zimbabwe. Furthermore, the CBC provided Megamelus scutellaris for water hyacinth
(Pontederia crassipes) and Cyrtobagous salviniae for Kariba weed (Salvinia molesta), marking the resumption of classical weed biocontrol activities in Zimbabwe.
The release of these agents has resulted in significant impacts on the target weeds with an 80% reduction in Kariba weed cover at two sites within a year of releasing C. salviniae. In addition, the collaboration is initiating the first ever complete biocontrol programme from agent selection, host specificity testing to release in Zimbabwe with the weevil Listronotus cinnamomeus for the management of Amazon Frogbit, Hydrocharis (=Limnobium) laevigata. Finally, work is ongoing to transfer the successful Australian Acacia management programme to Zimbabwe which may provide conservation of the critically endangered grassland bird, the blue swallow, the lifeline it desperately needs. This is part of the CBC’s broader strategy to capacitate southern African countries to effectively deal with invasive alien plants. Current experiences highlight the need to strengthen collaboration between countries, research institutions, and policymakers to ensure sustainable and effective biocontrol measures.
Photos above. Salvinia molesta infestation before (left) and after release of the biocontrol agent, Cyrtobagous salviniae (insert) at Chinyika Dam in Zimbabwe.
Photo top right. Flower galls and subsequent seed reduction on Lantana camara by a naturally dispersed biocontrol agent, Aceria lantanae, in Zimbabwe.
Photo bottom right. Participants at a workshop to draft the national action plan for the management of invasive alien species in Harare, September 2023.
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