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Landscape-scale management of invasive Cymbopogon afronardus (Stapf) in the rangelands of Uganda

Author: Stella Kabiri-Marial, Department of Crop Systems Analysis, Wageningen University and Research centre, the Netherlands

Date: 28/03/2014

Introduction:

Mrs Kabiri, who won the second prize of the Young Professionals in Science competition, said to Knowledge for Development that mapping Cymbopogon afronardus in Uganda had shown the unprecedented scale of the weed’s invasion. ‘I observed that an essential oil from C. afronardus controls Cyperus rotundus, another weed severely affecting crop production in Africa. C. afronardus is a cheap and environmentally friendly alternative for selective biological weed and pest control in high value crops. Moreover, its harvesting will improve the quality of rangeland pastures.’ She continued: ‘The award gave me confidence as a scientist. It made me realise that my research is important for society and that, in its own small way, it contributes to improving food security. I hope that in five years I am a reputable scientist who contributes towards the consolidation of food security and poverty alleviation in sub-Saharan Africa.’    


 

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Cymbopogon afronardus is an unpalatable, extremely rabid plant invader encroaching on the pastures of Uganda’s cattle corridor. Commonly known as Muteete grass, its growth is encouraged on rangelands mainly by overgrazing and burning. It is also associated with a significant reduction in animal production. Yet Cymbopogon can provide income for farmers and pastoralists: it provides good thatching and mulching material, and produces pungent and volatile essential oils that make it unpalatable to grazers.   

Research was conducted to: (i) estimate the extent of the acreage covered by Cymbopogon growth in the study area; (ii) evaluate the landscape characteristics and its ecological impact on threatened vegetation; and (iii) identify the allelopathic properties of Cymbopogon oil extracts and its potential as natural pest control.  

Satellite images of the rangelands in Uganda’s Kiruhura district were used to develop a map of the spatial distribution and habitat niche. Results revealed that 11% of the country’s rangelands and 61% of the Kiruhura district were invaded by Cymbopogon, most notably in open woody savannah on steep, north facing slopes with less eroded nutrient rich soil. According to Kabiri, more studies are required on invasion mechanisms and rangeland ecosystem dynamics to understand what facilitates the spread of Muteete grass.  

In terms of allelopathic properties, at even very low concentrations, experiments showed Cymbopogon essential oil had negatively impacted seed germination, root and shoot growth of Lolium perenne (ryegrass) and Cyperus rotundus (sedge), exposing the oil’s potential for natural bio-herbicide formulation.  

Research communication targeted a diversity of stakeholders to raise awareness of the extent of Cymbopogon’s invasion in Uganda’s cattle corridor. Data and results of the analysis helped in the preparation of a national invasive species strategy. A report was also submitted to ENDURE Network. The success of Cymbopogon detection and landscape characterisation from the Landsat imagery established a basis for a landscape-scale regional control strategy and a baseline for monitoring future spread.   

28/03/2014