COWPEA YIELD LOSSES ATTRIBUTED TO STRIGA INFESTATIONS

Experiments using cultivars with differing degrees of striga resistanc e were conducted at two sites at Kamboinse in 1988 and at two location s (Kamboinse and Kouare) in 1989 in the Sudan-Savannah region of Burki na Faso. At each site, striga free (SFP) and striga-infested plots (SI P) were selected. Two factors, location and genotype, were found to be associated additively with yield losses in soils infested by striga. The location effect was probably due to lower soil fertility in the SI P than the SFP plots under farming conditions. Yield losses in SIP rel ative to SFP ranged from 3.1%, at the experimental station, to 44.2% u nder farmers' field conditions. The genotype effect was evident at all locations. Depending on the susceptibility of the cultivars, it varie d from 3.1 to 36.5% of the mean yield of SFP with an average of 31.4% in susceptible cultivars. The location effect was evident only at Koua re, where SIP plots were under continuous cultivation without appropri ate soil fertility maintenance and/or restoration measures. This amoun ted to c. 19.4% of the mean yield in the SFP. To reduce yield losses i n soils infested by striga, it appears to be necessary to grow high yi elding, striga-resistant cultivars using agronomic practices which are known to improve soil fertility.