Responses of Tolerant and Susceptible Maize Varieties to Timing and Rate of Nitrogen under Striga hermonthica Infestation

Abstract Purple witchweed Striga hermonthica (Del.) Benth., here called just striga, parasitizes cereal crops in the savanna zone of sub‐Saharan Africa. The objectives of this study were to investigate the expressions of a tolerant and a susceptible cultivar of maize ( Zea mays L.) to striga as affected by timing (0, 2, 4, and 6 wk after maize planting) and rates (60 and 120 kg N ha −1 ) of N application under striga infestation. The experiment was designed as a split‐split plot with four replications. Timing of N application and N rates significantly affected striga emergence, host‐plant damage scores, agronomic traits, and grain yield. Nitrogen rate x application time interaction was highly significant for striga emergence. Time of N application was more important than N rate in suppressing striga emergence and host‐plant damage. Nitrogen application at 2 wk after planting and 120 kg N ha −1 gave the best result in terms of maize performance and reduction of striga emergence. Host‐plant damage symptoms were more useful in differentiating response of host genotypes to striga than striga emergence values. The tolerant cultivar (hybrid 8322‐13) produced 188% higher grain yield than the susceptible cultivar (hybrid 8338‐1) across all treatments. Grain yield of the tolerant cultivar at 60 kg N ha −1 was 88% higher than that of the susceptible cultivar at 120 kg N ha −1 . The tolerant cultivar produced an average 157% more ears at 60 kg N ha −1 and 51% more ears at 120 kg N ha −1 than the susceptible cultivar. Among all the factors studied, the most important component for striga management was genetic tolerance, the ability of a host plant to withstand the parasite.