Understanding the present distribution of parasitic weeds of the genus Striga and predicting its potential future geographic distribution in the light of climate and land use change

Parasitic weeds of the genus Striga (Orobanchaceae) cause considerable yield losses, especially in the savanna regions of Sub-Saharan Africa (Sauerborn et al. 2003). The geographic distribution and the infestation level of Striga are steadily increasing, particularly in Sub-Saharan Africa (Emechebe 2004, Ejeta 2007). There are different explanations for this trend such as trade and transport of contaminated seeds, cattle movement between fields, dispersal of Striga seeds through wind and surface water flows and lack of knowledge and means to control Striga (Berner et al. 1994). The main driving forces for the increase of the Striga problem, besides convenient climate, however, are (1) reduced soil fertility (Sauerborn et al. 2003), (2) increased land use, mostly on depleted soils and (3) expansion of the area cropped with susceptible host crops (Gressel et al. 2004). Future climate change may further influence the geographic distribution and invasive potential of Striga as habitats suitable for Striga growth might expand and/or shift to new areas (Mohamed et al. 2006).

As Striga is a major constraint to agriculture of the semi-arid regions in Sub-Saharan Africa, Striga´s actual and future distribution needs to be estimated urgently, in order to better and more efficiently target available Striga management strategies. Using innovative GIS-based modeling complemented by greenhouse and field studies, this project aims to better understand the present geographic distribution of Striga species and to predict potential future expansion areas of these dangerous weeds. Parameters determining the presence or absence of Striga will be analyzed and available data complemented by new studies on Striga ecology and seed bank dynamics.