IITA IPM project 26: Biological control of Imperata cylindrica in West Africa using fungal pathogens

Duration: 3 years (2003 to 2006)

Purpose: To characterise the morphological and genetic differences between biotypes of the weed originating from southeastern USA and West Africa and to test potential biocontrol agents against the West African biotype of I. cylindrica

Background/description: Imperata cylindrica [(L.) Raeuschel] reduces the yield of crops and causes the abandonment of agricultural land for resource poor farmers in West Africa. Existing control strategies are not preventing the spread of this noxious, rhizomatous grass. This study aims to develop an environmentally friendly, sustainable and selective method using fungal pathogens. In order, to understand the variance of Imperata cylindrica, samples of biotypes from across Africa are being characterised morphologically and genetically and compared with biotypes found in the south-eastern United States. Surveys for fungal pathogens in West Africa have yielded the potential biocontrol agents Colletotrichum caudatum and Glomerella cingulata. In addition, Drechslera gigantea and Exserohilum rostratum have been recovered. The latter are of interest as isolates of these species from the USA have shown efficacy in bioherbicide preparations against an US biotype of I. cylindrica and other weed grasses. Conversely, it is possible that a biotrophic pathogen may be a suitable control agent through its action as a physiological sink, depleting reserves stored in the rhizomes of I. cylindrica. It is the stored carbohydrate in the rhizomes which facilitates this weed’s competitive advantage to rapidly produce leaves following disturbance to the ecosystem e.g. in slash and burn agriculture. Isolates of the biotrophic pathogen Puccinia rufipes have been recovered in West Africa. This pathogen has also been observed, along with other biotrophs, in South Africa, where I. cylindrica is not considered a weed.

Agroecozone(s) and location(s): Humid and sub humid zones

Expected outputs: a) Characterisation of differences in the host between biotypes in the southeastern US and West Africa; b) Improved understanding of the variance of the host in order to assign the appropriate biological control option; c) Development of methods to produce uniform I. cylindrica plants for experimentation; d) Selection of plant pathogens with increased virulence for I. cylindrical; e) Epidemiological records for the most virulent plant pathogens; f) Development of preliminary mycoherbicide formulations

Potential impact and beneficiaries: Techniques will be developed to enable the further characterization of this weed from other geographical locations e.g. genetic mapping techniques. Preliminary mycoherbicide formulations of plant pathogens developed and ready for testing within IPM programmes such as those led by SP-IPM or other IITA projects.

Partners: a) University of Florida, USA; b) Plant Protection Research Institute, RSA; c) Service de la Protection des Vegetaux, Benin

Development investor(s): USAID

IITA contact person(s)/principal investigator(s): Fen Beed F.Beed@cgiar.org website http://www.iita.org