Influence of Cropping Pattern Systems on Incidence of Scab and Septoria Leaf Spot Disease of Cowpea (Vigna unguiculata)

Abstract

Aims: Scab caused by Sphaceloma sp and Septoria leaf spot caused by Septoria vignae were evaluated on one variety (Ife Brown) of cowpea: in this study. Ife Brown is highly susceptible to scab and moderately susceptible to Septoria leaf spot. Cowpea (Vignia unguiculata L. Walp) was planted simultaneously with maize (intercrop) and sorghum (intercrop). The scientific importance of intercropping pattern in this study was to develop an information based system on how crop pattern can influence disease incidence and severity and thus improve crop yield within an agro ecological zone Study Design: The field layout was factorial concept in Randomized Complete Block Design (RBCD) with four replications Place and Duration of Study: The two cereals used for this study were, maize variety TZEEW, and sorghum variety ICSV111. The investigations were carried out during three cropping seasons of 2004, 2005 and 2006 at Samaru and Shika in Zaria, Nigeria. Methodology: Five cropping patterns: interrow, intrarow, doublerow, strip and sole cropping on the incidence and severity of scab and Septoria leaf spot fungi isolated from infected field plants, were studied. Disease incidence and severity for scab and Septoria leaf spot were recorded at weekly intervals starting from the first appearance of the symptoms. Data for the different plant parts (leaf, stem, peduncle, flower cushion and pod) infected by scab and leaves infected by Septoria leaf spot were recorded from four middle ridges for each plot. The data obtained was subjected to analyses of variance (ANOVA) and mean separation was by Student Newman Keuls Test (SNK). Results: Infection of the cowpea and severity of scab and Septoria leaf spot on the crop significantly increased with increase in age of the variety tested. Symptoms of infection resulting from scab were seen on all the aerial parts of the crop from seedling stage to maturity, depending on the time of infection. Cropping patterns significantly affected the incidence and severity of the two fungi on cowpea in the order of sole<double-row<strip<inter-row<intra-row for scab and sole<intra-row<double-row<strip<inter-row for Septoria leaf spot. However, the reaction of the crop to the individual pathogens was different across the various cropping patterns with the rate of infection of scab higher compared with that of Septoria leaf spot. Cowpea sole cropping proves better for both pathogens compared to the other cropping patterns. Conclusion: This study showed that sole cropping system was more ideal for disease managements and incidence of Scab and Septoria leaf spot diseases of cowpea with respect to cropping systems studied.