Cercospora leaf spot (CLS) and Alternaria leaf blight (ALB) diseases are major constraints to sesame production. Although disease management through intercropping of sesame with maize and foliar-spray with extracts of Tithonia diversifolia have been found to be effective, the frequency of application of the extracts required to achieve optimal disease control have not been determined. Therefore, a study was carried out to determine the effect of frequency of application of T. diversifolia extract on CLS and ALB diseases of sesame intercropped with maize during the early (June – September) and late (August – November) cropping seasons of 2011. Field experiments laid out in a Randomised Complete Block design and in a split plot arrangement with three replications were conducted in Ejigbo, Nigeria. Treatments consisted of aqueous Tithonia diversifolia leaf extract applied at 7.0, 7.5 or 8.0 % (w/v) in one-, two- or three- spray regimes at 2-week intervals from three weeks after planting (WAP) to plots of sesame intercropped with maize; Unsprayed sesame/maize intercrop; sesame/maize intercrop sprayed with Carbendazim (50 %)WP and unsprayed sole sesame plots. Results revealed that CLS and ALB incidence, severity and defoliation were significantly (p < 0.05) reduced by three-spray regime of 7.5 % (w/v) T. diversifolia extract. The efficacy of 7.5 % (w/v) T. diversifolia extract was comparable to that of 8.0 % (w/v) T. diversifolia extract or synthetic fungicide (Carbendazim 50 %WP). This study showed that the three-spray regime of 7.5 % w/v T. diversifolia leaf extract is sufficient to control foliar diseases of sesame intercropped with maize.
