Major, minor and potential parasitic weeds in semi-arid tropical Africa: the example of Scrophulariaceae.
The parasitic Striga spp. found in African savannas are reviewed. Their diversification from natural vegetation to cultivated fields, and their increase in numbers over time until they become major pests, are outlined. Major and minor parasites, occasional parasites and potential parasitic weeds are described. An awareness of the possible evolution of minor and occasional Orobanche weeds into major pests is also discussed.