EFFECT OF SOILS, CROPPING SYSTEM AND HOST PHENOTYPE ON INCIDENCE AND SEVERITY OF STRIGA GESNERIOIDES ON COWPEA IN WEST-AFRICA

Striga gesnerioides, a plant parasitic phanerogam, is a known constrai nt to cowpea production in the sahelian and northern guinea savanna zo nes of West and Central Africa. A survey was done in 1990 across six c ountries to collect data on soil types, cowpea phenotype, and cropping systems with relation to incidence and severity of striga on cowpea. Of the 153 fields visited, 40% were infested with S. gesnerioides, Gen erally, the severity of the parasitic weed was light, with a mean rati ng of 1.5 on a scale of 1 to 5. A high correlation was found between i ncidence of striga and the amount of sand in the soil. Of the 153 site s only 27 had no sand in the soil. Of those 27, only three (11%) had s ome S. gesnerioides compared with 50% on sandy soils. A database was c ompiled on cowpea phenotypes and the cropping systems in which they ar e used. Severity of striga infestation per cowpea plant decreased some what from east to west, though it is unclear whether this was a functi on of cowpea genotype or striga pathotype. The predominant cropping sy stems where striga infestation occurred were sole cowpea, intercrop wi th millet, and with sorghum. Fields in rotation with cotton, or interc ropped with vegetables and legumes were always striga-free.